Phytoliths from subantarctic Campbell Island: plant production and soil surface spectra

Review of Palaeobotany and Palynology 132 (2004) 37 – 59 www.elsevier.com/locate/revpalbo

Phytoliths from subantarctic Campbell Island: plant production and soil surface spectra Vanessa Clare Thorn * Antarctic Research Centre, Faculty of Science, Victoria University, P.O. Box 600, Wellington, New Zealand Received 15 September 2003; accepted 6 April 2004

Abstract Phytolith (plant opal) production, and its preservation within the soil surface, is described for the first time in the subantarctic region from Campbell Island, ca. 600 km south of New Zealand, forming the basis for a new modern reference collection for the region. Plant samples (many from species endemic to the island and vegetation community dominants) were sourced from Campbell Island and from gardens in New Zealand. Short and long cell phytoliths are described from four graminoids (Chionochloa antarctica, Poa litorosa and Poa sp. (Poaceae), Carex trifida (Cyperaceae)), four forbs (Acaena minor var. antarctica and Acaena anserinifolia (Rosaceae), Myosotis capitata (Boraginaceae), Anaphalioides bellidioides (Asteraceae)) and a shrub (Hebe elliptica (Plantaginaceae)) from 23 analysed taxa. The remainder were found to be non-producers, including the distinctive macrophyllous forbs or ‘megaherbs’. Soil surface samples collected with 11 of the plants from Campbell Island contain abundant, predominantly graminoid-type phytoliths. Two-sample Kolmogorov-Smirnov tests indicate the soil surface assemblages beneath different vegetation community types are nevertheless similar to each other. This is interpreted to be a direct result of widespread grasses in the island’s vegetation that produce abundant phytoliths of robust morphology. The overrepresentation of grass phytoliths in the soils may also be explained by the absence of other non-grass phytolith producer taxa in the vicinity of the collection locality, or the dissolution or fragmentation in the soil of fragile forms. Localised concentrations of sedge ‘hat-shaped’ phytoliths in two soil surface samples result in significantly different assemblages from the other collection sites, suggesting that despite the high proportion of grass-type phytoliths, there is still potential for differentiating vegetation community types on Campbell Island on the basis of the dispersed soil surface assemblages. With further knowledge about modern phytolith production in the subantarctic, this technique may then be applied to regional fossil assemblages. The predominantly grass-type phytoliths described during this pilot study differ significantly from the Oligocene and Miocene tree/shrub-dominated assemblage of the Cape Roberts Project cores from the Ross Sea region of Antarctica, interpreted to have been sourced from a vegetation growing in similar, but less oceanic, climatic conditions. The reasons for this disparity, reflected by the terrestrial palynomorph records of previous studies undertaken on the Cape Roberts Project cores and present day Campbell Island pollen rain, remain unclear, but may involve differences in the growing environment or different continental origins of elements of the vegetation. D 2004 Elsevier B.V. All rights reserved. Keywords: phytoliths; Campbell Island; subantarctic; New Zealand; Antarctica

1. Introduction * Fax: +64-4-463-5186. E-mail address: [email protected] (V.C. Thorn). 0034-6667/$ - see front matter D 2004 Elsevier B.V. All rights reserved. doi:10.1016/j.revpalbo.2004.04.003

Campbell Island (52j34VS, 169j09VE) is one of several isolated islands scattered throughout the

38

V.C. Thorn / Review of Palaeobotany and Palynology 132 (2004) 37–59

Southern Ocean between mainland New Zealand and the Ross Sea region of Antarctica, in cool waters midway between the Antarctic and Subtropical Convergences (Fig. 1). Many of the islands in this climatically sensitive zone are ideal sites for studying past environmental change due to relatively little human disturbance, diverse vegetation and extensive peat cover (McGlone, 2002). Previous studies have investigated the modern and Quaternary terrestrial palynology (McGlone et al., 1997; McGlone and Meurk, 2000) and the distribution and taxonomy of the modern vegetation is well known (Meurk, 1975, 1980; Meurk et al., 1994). This study presents descriptions of plant phytoliths (the first in the subantarctic region) and investigates phytolith preservation and assemblage diversity in the organic soil surface accumulating under different vegetation community types. Phytolith analysis is a developing discipline of micropalaeontology and has been applied in archaeological, palaeoecological, edaphic and botanical contexts, complementing and supplementing the terrestrial palynomorph record. Phytoliths are microscopic bodies that are formed by the solidification of silica gel that collects within and between the cells of many plants. They vary significantly in morphology and are typically between f 5 and 200 Am in size. Increasingly, studies of phytolith production in modern plants are allowing the identification of the source plant to family, generic or even species level from distinctive morphotypes (e.g. Piperno, 1985, 1988; Kondo et al., 1994; Runge, 1996; Kealhofer, 1998; Piperno and Pearsall, 1998; Carnelli et al., 2001). This is despite the challenge of many different morphologies forming within a single plant or species (known as ‘multiplicity’) and similar morphologies forming across several species (‘redundancy’) (Rovner, 1971). To attempt an interpretation of the source vegetation based on dispersed phytoliths within the soil surface it is important to consider the potential methods of phytolith transport and entrainment prevalent at the study site. When a phytolith-producing plant dies in a sheltered site the organic matter decays from around the phytoliths and releases them directly into the soil. If the soil is stable, an in situ record of the presence of the plant is preserved and over time the soil phytolith content

would increase in volume as phytolith-producing plants grow, die and decay above that site, resulting in a long-term, site-specific record of the vegetation cover. However, once released in open or unstable sites, although not produced by the plant to be dispersed for reproductive purposes, phytoliths are known to be transported, sometimes over considerable distances, by wind (Baker, 1959; Twiss et al., 1969; Bowdery, 1999; Romero, 1999) and are subject to any erosion, transport and depositional processes undergone by the enclosing soil. Other factors that may affect the phytolith assemblage include dispersal due to fire and animal grazing (Fredlund and Tieszen, 1994; Hart, 1997; Gobetz and Bozarth, 2001) and chemical dissolution. Residence times of phytoliths in soil are not well known, but occasional etching of phytoliths and the apparent propensity of ‘robust’ forms in soil (and sediment, further down the transport pathway) assemblages suggests that dissolution increases with depth beneath the soil surface (or sea floor, in the case of marine sediments). This pilot study assesses phytolith production in a selection of 23 plant taxa known to occur naturally on Campbell Island, eight of which are dominant species in the vegetation (Table 1). From the vascular flora, of the Pteridophyta, two Filicopsida (fern) taxa were analysed, but no representatives of the Psilopsida or Lycopsida. Four taxa were analysed from seven Liliopsida (monocotyledon) families and 16 taxa from 36 Magnoliopsida (dicotyledon) families. These samples have been sourced from both Campbell Island and localities in New Zealand. A suite of 11 soil surface samples collected directly beneath the Campbell Island plant samples are also analysed and their assemblages compared, using the two-sample Kolmogorov-Smirnov test to assess any differences between the assemblages accumulating under different vegetation community types. The phytolith reference collection created as part of this study provides a comparative database for both modern and Quaternary phytolith studies on the subantarctic islands. The new information will also supplement existing knowledge of New Zealand phytoliths (Weatherhead, 1988; Kondo et al., 1994), particularly from ecologically similar subalpine habitats. As this database becomes more comprehensive over time with further collections

V.C. Thorn / Review of Palaeobotany and Palynology 132 (2004) 37–59

39

Fig. 1. Campbell Island locality maps. (a) Campbell Island in relation to New Zealand and the Ross Sea region, Antarctica (not to scale); (b) Campbell Island geography and area where samples were collected; (c) Enlargement of boxed area in (b). Star symbols mark the exact localities of plant and soil surface sample collections a to g. Arrows represent the direction of surface run-off from each locality. Collection h is known only to have been collected on Mt. Lyall.

40

V.C. Thorn / Review of Palaeobotany and Palynology 132 (2004) 37–59

Table 1 Campbell Island modern native plant taxa processed for phytoliths and collection localities Plant type

Family

Macrophyllous forb

Apiaceae (D)

Subfamily

Liliaceae (M) Asteraceae (D)

Other forb

Rosaceae (D) Asteraceae (D) Boraginaceae (D) Arundinoideae Pooideae

Species

Collection localitya

Anisotome antipoda Anisotome latifolia Stilbocarpa polaris Bulbinella rossii* Pleurophyllum criniferum Pleurophyllum hookeri Pleurophyllum speciosum

CI CI CI CI CI CI CI

Acaena anserinifolia* Acaena minor var. antarctica Anaphalioides bellidioides Myosotis capitata

OBG OBG OBG INV

Chionochloa antarctica Poa litorosa* Poa sp.

CI e INV CI b

a b b c c d a

Grass

Poaceae (M)

Sedge

Cyperaceae (M)

Carex trifida

INV

Shrub

Rubiaceae (D) Ericaceae (D)

Myrsinaceae (D)

Coprosma sp. Dracophyllum longifolium* Dracophyllum scoparium* Hebe benthamii (bWELTU 6644) Hebe elliptica* Myrsine divaricata*

CI e CI f CI f CI h VUW CI g and OBGc

Pteridaceae Dryopteridaceae

Histiopteris incisa Polystichum vestitum*

OBG OBG

Plantaginaceae (D)

Fern

D = dicotyledon family; M = monocotyledon family; *= dominant species of certain Campbell Island vegetation communities, after Meurk et al. (1994). a CI a – h = Campbell Island collection localities, refer to Fig. 1; INV = Queen’s Park, Invercargill, New Zealand; OBG = Otari Botanic Gardens, Wellington, New Zealand; VUW = Victoria University of Wellington Ground, New Zealand.

and analyses from not only Campbell Island, but throughout the subantarctic region, it will provide the nearest available analogues, despite the antiquity of the sediments, for dispersed phytolith assemblages recovered from the Antarctic continent (Carter, 1998; Thorn, 2001).

2. Campbell Island—environment and vegetation Subantarctic Campbell Island lies f 600 km SSE from South Island, New Zealand with its nearest neighbour being the larger Auckland Island group, which lies 300 km to the NW. Campbell Island is formed from the remains of a dissected Pliocene volcanic cone with U-shaped lowland valleys and higher plateaux and ridges reaching up to a maximum

altitude of 570 m. The U-shaped valleys are considered to be evidence for substantial glaciation on the island during the Last Glacial Maximum (McGlone et al., 1997). The majority of the island is covered with peat or peaty soils up to ca. 5 m thick, which tend to slide on the steeper slopes after heavy rainfall (Campbell, 1980). The climate of Campbell Island is dominated by the prevailing W –WNW winds and is cloudy, moist and cool (De Lisle, 1965). The most prevalent wind speeds are 40 – 50 km/h, although finding a representative measurement site is difficult. The island averages 215 days a year with less than 1 hour of sunshine and has moderate rainfall of 1400 mm year 1, usually falling as light rain or drizzle. Air temperatures vary little annually and over a diurnal cycle, with snowfall possible during any month (De

V.C. Thorn / Review of Palaeobotany and Palynology 132 (2004) 37–59

Lisle, 1965). Sea-level mean monthly air temperatures approximate sea-surface temperatures and lie around 6.5 jC in August and just over 9 jC in February (New Zealand Meteorological Service, 1973; McGlone et al., 1997). The soils of Campbell Island form under relatively undisturbed vegetation over a large area (Campbell, 1980; Arand et al., 1991). They are organic soils and dominated by organic matter throughout their profile with a high capacity for water absorption. They are also typically acidic (pH 3.0 –4.5) and have low fertility. Organic soils form as blanket peats in subalpine regions of New Zealand, including the subantarctic islands, where the climate is cool and wet. Due to poor drainage and aeration, there are few soil organisms, resulting in an undisturbed stratigraphy where there has been no soil creep or slip. The modern vegetation of Campbell Island is a mosaic of near-pristine, reduced, induced and heavily modified/grazed communities due to the introduction in the 1930s and subsequent elimination in the 1990s of domestic sheep and cattle (Meurk et al., 1994). Descriptions of the vegetation, before and after this period, include those of Cockayne (1904, 1909), Oliver and Sorensen (1951), Given and Meurk (1980) and Meurk (1975). The most recent and comprehensive studies have produced a vegetation map of the island (Meurk and Given, 1990) and provided a comprehensive analysis of the vegetationenvironment pattern using multivariate statistics (Meurk et al., 1994). The Campbell Island flora is generally low in stature due to the extremely exposed maritime conditions and consists of 132 indigenous vascular taxa and 39 naturalised adventives. Meurk et al. (1994) identified 21 plant communities, into which McGlone and Meurk (2000) have simplified the non-cushion bog vegetation into six major groupings: maritime turf and grassland, Carex flushes, forest-scrub, shrub-tussock, tussock grasslands and tundra. Distinctive components of the vegetation are the macrophyllous forbs (commonly referred to as ‘megaherbs’), which are large-leaved herbs with colourful flowers. Taxa in this group include members of the Apiaceae (Anisotome antipoda, Anisotome latifolia, Stilbocarpa polaris), Liliaceae (Bulbinella rossii), and Asteraceae (Pleurophyllum criniferum, Pleurophyllum hookeri, Pleurophyllum speciosum).

41

3. Materials and methods 3.1. Plants To begin a modern phytolith reference collection for Campbell Island samples of individual plants ( f 10 g fresh weight) were sought for destructive processing to extract their phytolith content. Samples were sourced from Campbell Island itself and also from taxa known to occur in the Campbell Island flora, but growing on New Zealand soil (Table 1). The selection of species analysed was restricted to the availability of samples from these sources in lieu of Campbell Island fieldwork. All but two of the plants sourced were identifiable to species level. In total, 24 samples were processed from 23 species (including two samples of Myrsine divaricata (Myrsinaceae) from different localities). These 23 species represent two fern, three monocotyledon and nine dicotyledon families, including eight dominant components of Campbell Island vegetation community types (after Meurk et al., 1994). All but one of the 14 plants sourced directly from Campbell Island were collected during a 1995 visit by New Zealand Department of Conservation (DOC) staff, who simultaneously collected soil surface samples at each collection site. The 13 plant specimens consisted of leaf and stem material from seven species of macrophyllous forb, two grass species and four shrub species (Table 1). The seven collection localities (Fig. 1 and Table 1) range in altitude from sea level to 250 m above sea level (masl) and are oriented in an approximately NW transect in the centre of the island. The prevailing winds blow approximately parallel to this transect and the surface water run-off flows into three separate stream catchments. The collection localities are within four different vegetation community types (CT) as defined by Meurk and Given (1990) and Meurk et al. (1994). Localities a, b and d are within areas of low alpine equivalent induced vegetation dominated by Poa litorosa (Poaceae) in turf short tussock meadows with a seasonal prominence of Bulbinella rossii (CT = P; Meurk and Given, 1990). The remainders of the localities are within areas of semi-natural vegetation. Localities c and e are within low alpine equivalent areas of Coprosma (Rubiaceae) – Myrsinefern swamp shrubland to scrub (CT = Co). Locality f

42

V.C. Thorn / Review of Palaeobotany and Palynology 132 (2004) 37–59

is located in a subalpine equivalent dwarf forest and scrub zone dominated by Dracophyllum (Ericaceae) and Myrsine with Coprosma and ferns in the lower strata (CT = Df). Finally, locality g is within a maritime tall tussock grassland zone dominated by P. litorosa (CT = Pm). The destructive methodology involved in phytolith extraction precluded several New Zealand herbariums as sources of additional samples. However, the Victoria University of Wellington Herbarium was able to provide a sample of Hebe benthamii (Plantaginaceae, voucher number WELTU 6644) from a plant that had been collected from Mt. Lyall on Campbell Island in 1966. Precise collection location details are not available (Locality h, Fig. 1). The remaining nine plant taxa sampled were collected from plants growing on New Zealand soil. Otari Botanic Gardens in Wellington provided cuttings from three forbs (Acaena anserinifolia and Acaena minor var. antarctica (Rosaceae), and Anaphalioides bellidioides (Asteraceae)), two ferns (Histiopteris incisa (Pteridaceae) and Polystichum vestitum (Dryopteridaceae, originally sourced from Campbell Island)) and one shrub (a Myrsine divaricata originally sourced from the Auckland Islands, to complement the sample sourced directly from the DOC Campbell Island collection). Four samples were supplied from plants originally sourced from the subantarctic Auckland Islands, but now growing in Queen’s Park, Invercargill, South Island, New Zealand. This collection included a forb (Myosotis capitata (Boraginaceae)), a grass (Poa litorosa) and a sedge (Carex trifida (Cyperaceae)). Hebe elliptica (Plantaginaceae), the final taxon analysed was collected in the grounds of Victoria University of Wellington. The lowland brown earth soils of Wellington and Invercargill differ from the Campbell Island organic soils and are typically developed on sedimentary rocks below 500 m altitude in southern North Island and 300 m in southern South Island. These areas have a moist, cool to mild temperate climate where rainfall is sufficient to maintain soil moisture between field capacity and wilting point throughout the year. The soil has typically a silt loam texture with moderate (20 – 35%) clay content (Molloy, 1998). The laboratory procedure for extracting phytoliths was designed to minimise the risk of contamination and included the use of fume hoods and Millipore-

filtered water throughout. A wet chemical oxidation method was used to extract phytoliths from plant material, using a strong oxidising agent to digest the organic materials causing the phytoliths to be released (Geis, 1973). Initial pre-treatment of the plant tissue involves removing any adhering debris or mineral material by washing in a 1 molar solution of HCl (3% dilution) and suspension in an ultrasonic tank. Following rinsing and drying, concentrated H2SO4 is added, and the sample left in a heated water bath for 4 h and then cooled overnight. The organic material is by now reduced to carbon and H2O2 (27%) is added causing an exothermic reaction. The opal residue is then washed and mounted on a glass microscope slide using Canada Balsam. Each slide was scanned on a Leica DMLB transmitted light microscope at 400  magnification. A count of 300 individual phytoliths was recorded for each of the diverse Poaceae samples and the presence of distinctive phytolith morphotypes noted in the remaining taxa. Distinctive phytoliths were photographed at either 400  or 1000 , depending on their size, using a PIXERA digital camera. 3.2. Soil surface samples Grab samples were collected from the leaf litter or uppermost soil surface (O horizon) accumulating directly beneath 11 of the plants sampled on Campbell Island (Table 3). Only one sample was collected beneath adjacent Dracophyllum longifolium and Dracophyllum scoparium plants (Ericaceae) at locality f. One sample was collected at each locality except for locality b (3 samples) and localities a and c (2 samples each). The air-dried macroscopic characteristics of these samples were similar, including peaty soil particles (some with quartz grains), leaf fragments (both monocotyledon and dicotyledon), root, stem, seed and flower fragments. Only the Bulbinella rossii sample contained no peaty soil particles, being entirely composed of leaf litter. The laboratory procedure used to extract phytoliths from these organic-rich soil samples is modified from Pearsall (2000). The air-dried samples were slightly crushed and the >250 Am fraction and oversized leaf litter removed. Each sample was weighed pre- and post-processing to quantatively assess phytolith content. Each sample was then treated with 10% HCl to

V.C. Thorn / Review of Palaeobotany and Palynology 132 (2004) 37–59

remove carbonates. Following washing, concentrated H2SO4 and H2O2 was added to digest the organic material, as during the plant processing procedure. After thorough washing, a heavy-liquid flotation procedure using non-toxic Na6(H2W12O40)
H2O (sodium polytungstate) at specific gravity 2.3 separated the biogenic from the inorganic silica. The residue, which may also contain diatoms and other soil biogenic silica, was then thoroughly washed, dried and weighed. The microscope slide preparation and examination techniques were the same as for the plant material. Counts of 300 individual phytoliths were completed for each soil surface sample. 3.3. Phytolith classification The method and terminology of phytolith description and naming is currently under review within the phytolith research community to attempt a global standardisation of nomenclature. To date, many different classification schemes have been suggested (e.g. Twiss et al., 1969; Brown, 1984; Mulholland and Rapp, 1992; Pearsall, 1992; Piperno and Pearsall, 1998; Piperno et al., 1999; Bowdery et al., 2001), which have been variously employed and modified by authors with respect to the particular material under study. It is generally agreed that nomenclatural stability would greatly facilitate the comparison between phytolith types encountered by different researchers, resulting in a draft version of an International Code for Phytolith Nomenclature (ICPN, Madella et al., 2003). The ICPN committee is charged with the task of developing a standard protocol for describing and naming new phytolith types and a glossary of descriptors akin to other such protocols already in use by other scientific disciplines. To be generally applicable the ICPN has to be capable of encompassing the enormous variety of phytolith types (specifically adequately describing three-dimensional form), include terminology easily applied and translated between different languages and have total unambiguity in the definition of descriptor terms. An attempt was made in this study to apply the initial draft version of the ICPN (v. 1.0, Madella et al., 2003) to the phytolith morphologies encountered. On practical application, difficulties were encountered confidently assigning suitable descriptors for particular morphologies and some additional terms were

43

required. It was found that where applicable to some forms (e.g. globular rugulate), for others the use of only two descriptors (shape, and surface texture and ornamentation) to name a phytolith type (without knowledge of anatomical origin) is only sufficient to classify a particular morphotype within a broad group (e.g. Conical psilate) and does not adequately convey the differences between distinctive forms. This effectively ‘lumps’ morphologies that are significantly different into broader groups than previously used and makes the recognition of particularly distinctive forms as separately named morphotypes difficult. Consequently, the phytolith morphotype classification used in this study is based on anatomical origin (where undisputed, for example, stomatal guard cells) or non-taxonomic terms based on Mulholland and Rapp (1992). 4. Results 4.1. Plant phytolith production Of the 23 species analysed, nine produced phytoliths from six families, in quantities from trace amounts to ca. 5% of dry weight (Table 2). These included dicotyledon forbs and one shrub, and monocotyledon graminoids (sedge and grasses). The macrophyllous forbs, ferns and all but one of the shrub species were non-producers. A variety of morphotypes were encountered from the producer species, including typical ‘short-cell’ grass phytoliths, ‘hat-shaped’ forms typical of sedges, irregular forms, and epidermal and tracheid cell phytoliths. The plants that produced phytoliths are discussed below by plant type and illustrated in Fig. 2. Forbs Asteraceae/Compositae, Anaphalioides bellidioides (G. Forst) Glenny 1997 Vernacular: Hells Bells Synonomy: Helichrysum bellidioides (G. Forst) Willd. The Asteraceae are the largest family of flowering plants and are comprised of herbs, shrubs and less commonly trees. The Campbell Island flora contains 19 species from this family (including several varieties). Helichrysum bellidioides var. prostratum is listed as having uncertain status in the Campbell Island flora

44 Table 2 Phytolith morphotypes and counts from Campbell Island modern plant taxa. Presence of a particular morphotype is indicated by a black dot for non-grass species and by short-cell counts for grass species Phytolith morphotypes

Anaphalioides Myosotis Acaena Acaena minor Carex Hebe Chionochloa Poa Poa sp. Main sum bellidioides capitata anserinifolia var. antarctica trifida elliptica antarctica litorosa of grass phytoliths 0.50 0.50 5.44 trace 0.22 0.09 0.61 2.29 1.40

% Phytolith by dry weighta

Rondel

Narrow base Sinuate Trilobate Short

Tall

Saddle Irregular

Elongate

Hat-shaped Trichome

Epidermal Stomata Tracheid

Mesophyll Total grass specimens a

1 Irregular Irregular Irregular Keeled Regular Conical Irregular Pointed

49 29 2 3 159 110 5 7 2

Narrow base Wide base Multifaceted Opaque Non-opaque Spinulose Psilate Spinulose Spirally thickened Undulose

6

32 31 9 106

190 15

2 2 1 1 5 1

113 1 1

1 4

2

1 49 29 8 3 159 32 331 29 113 2 2 2 1 1 119 6 1 2

.

Hair base Hair Hair base subsidiary cells Groundmass cells Guard cells Subsidiary cells Psilate Scalariform Spirally thickened Globular

. . .

Hollow Solid

.

.

. .

. .

1 10 1

1 10 1

300

902

. . . . . .

. . .

.

Phytolith percentage is based on a single sample of dried leaves, herbaceous stems and/or small twigs.

.

302

300

V.C. Thorn / Review of Palaeobotany and Palynology 132 (2004) 37–59

Bilobate Polylobate

V.C. Thorn / Review of Palaeobotany and Palynology 132 (2004) 37–59

(Given and Meurk, 1980). However, Helichrysum is noted as a constant dominant taxa within moderately high altitude, Marsippospermum tall turf rushland with megaherbs and low-moderate altitude, turf-mat-forbgrassland of disturbed, flushed sites (Meurk et al., 1994). It is also noted as a constant matrix taxa within two other community types and as a typical matrix component of five others. In New Zealand, Anaphalioides bellidioides is spread throughout South Island and North Island south of 37j30V latitude in lowland to montane and lower subalpine grassland and open shrubland (Allan, 1961, 2000). Reviews of current plant phytolith production suggest that members of the Asteraceae family are often common to abundant phytolith producers (Piperno, 1988; Pearsall, 2000). Metcalfe and Chalk (1983) note the presence of silica in the leaves of two Asteraceae genera (Brasilia and Helianthus). Piperno (1988) notes in a review of dicotyledon silicification patterns that the most common types of phytolith from selected members of the Asteraceae/Compositae family are epidermal anticlinal and polyhedral, hair cells and hair bases, with tracheid and mesophyll cells occurring less frequently. Bozarth (1992) noted polyhedral epidermal cells, anticlinal (or jigsaw-shaped) cells, spirally thickened tracheid cells, opaque platelets and segmented hairs in members of the Asteraceae. Runge (1996) noted segmented hair cells, hair bases, polyhedral epidermal cells and anticlinal cells in members of the Asteraceae/Compositae from East Africa. However, Ball (2002) found no phytoliths in a sample of Helichrysum sp. collected from the Dhofar region of Oman, and Wallis (2003) found only trace amounts or no phytoliths in four Asteraceae species processed from northwest Australia. Kondo et al. (1994) analysed five native trees from the Asteraceae family from New Zealand and found phytolith production varied from not present (Olearia avicenniifolia) to abundant (e.g. Olearia furfuracea). The most common morphotypes were tracheids and epidermal cells. The Anaphalioides bellidioides sample in this study produced small quantities of silicified spirally thickened tracheid cells and thin-walled, globulose cell linings. The rounded shape of the latter suggests they may have originated in mesophyll cells. These morphotypes have limited taxonomic value as neither of the forms are particularly distinctive and they are redundant, also occurring in other taxa analysed in

45

this study (Table 2). They are also fragile, so are unlikely to preserve for extended periods in the soil. Boraginaceae, Myosotis capitata Hook.f. 1844 Vernacular: Forget-me-not The Boraginaceae are a cosmopolitan family of herbs, a few lianas, shrubs and trees distributed from the tropics to the high northern and southern latitudes. Myosotis antarctica and Myosotis capitata are the only representatives of this family growing on Campbell Island (Given and Meurk, 1980). M. antarctica is a typical matrix species of the high altitude Bulbinella/ turf-forb-cryptogam fellfield/talus vegetation community type (Meurk et al., 1994) and is endemic to Campbell Island. M. capitata is more common in the Auckland Island flora, particularly in high altitude rocky places, and is stated as having a restricted distribution on Campbell Island by Given and Meurk (1980). M. capitata is endemic to Auckland and Campbell Islands. Pearsall (2000), Piperno (1988) and the University of Missouri Paleoethnobotany Laboratory (2002) state that members of the Boraginaceae family often produce common to abundant phytoliths and silica is noted within the wood of Cordia by Metcalfe and Chalk (1983). Polyhedral epidermal cells, non-segmented hair cells and hair bases are common phytolith types from this family (Piperno, 1988; Kealhofer and Piperno, 1998). Bozarth (1992) noted polyhedral epidermal cells, anticlinal cells, spirally thickened tracheid cells, mesophyll cells and rare segmented hair cells in members of the Boraginaceae with the polyhedral epidermal and anticlinal cells being produced by Myosotis verna. The Missouri Paleoethnobotany Laboratory notes that several Boraginaceae genera produce diagnostic phytoliths, including Myosotis (University of Missouri Paleoethnobotany Laboratory, 2002). The Myosotis capitata phytolith morphotypes are distinctive hair cells (both segmented and non-segmented) and hair bases with subsidiary cells (Fig. 2). Rare globulose possibly mesophyll cells are also present. The hair cells are typically large (those observed ranged in length from ca. 70 to 115 Am from the tip of the hair, before it flares to the hair base) and appear to consist of a central core and an outer sheath, perhaps representing two stages of silicification. Smaller (up to 35 Am long), segmented or hollow hairs, broken from their bases, with pointed apices are also present. The hair flares out towards the base into a circular, or

46

V.C. Thorn / Review of Palaeobotany and Palynology 132 (2004) 37–59

V.C. Thorn / Review of Palaeobotany and Palynology 132 (2004) 37–59

octagonal plate with low concentric and radial ridges on the upper surface. The hair base ranges from ca. 30 to 60 Am in diameter. This basal plate is commonly anchored in the centre of eight radially arranged circular to polyhedral subsidiary cells. The hair itself is commonly snapped off close to the basal plate (probably an artifact of the processing procedure) but occasionally remains entire. The hair apex is commonly rounded. It is expected that these forms would be fragile in the soil, perhaps resulting in only the base of the hairs preserving long term. The upper surfaces of the leaves of Myosotis capitata have abundant long and silky hairs, which reflects the distinctive hair cell and hair base phytoliths encountered. These phytoliths may prove to be taxonomically useful when further analysis of phytolith production within other Boraginaceae taxa is undertaken as similar forms have already been seen from members of the Boraginaceae from the Oman (Ball, 2002). Rosaceae, Acaena anserinifolia (J.R. Forst and G. Forst) J.B. Armstr. and Acaena minor var. antarctica (Ckn.) Allan comb. nov. Vernacular: Bidibid The Rosaceae comprise a family of trees, shrubs and mainly perennial herbs with members distributed from the high to the low latitudes. Acaena is the only naturally occurring genera of the Rosaceae on Campbell Island. Acaena spp. are herbs with a creeping habit. Acaena cf. anserinifolia is listed by Given and Meurk (1980) for the Campbell Island flora, together with Acaena minor var. antarctica and A. minor var. minor. Acaena spp. have since been shown to be components of ten vegetation community types with A. anserinifolia a constant dominant in moderate altitude, Bulbinella/turf-mat grassland and unspecified Acaena spp. constant dominants in mid altitude, biotic-seral, mat-turf herbfield (Meurk et al., 1994). A. anserinifolia also occurs throughout New Zealand from Southland to the tip of Northland (Allan, 2000). A. minor var. antarctica is a constant matrix species in sheltered-maritime Hebe elliptica-mixed tussockscrub (Meurk et al., 1994).

47

Phytolith production in the Rosaceae family ranges from zero to abundant (Piperno, 1988; Pearsall, 2000; University of Missouri Paleoethnobotany Laboratory, 2002) comprising mainly epidermal cells. Bozarth (1992) noted the production of polyhedral epidermal, anticlinal and mesophyll cells in Rosa blanda. Runge (1996) found epidermal cell and hair base cell phytoliths in Hagenia abyssinica from east Africa. Acaena anserinifolia and Acaena minor var. antarctica both produced distinctive non-segmented hair cell, hair base, hair base subsidiary cells and tracheid phytoliths (Fig. 2). The hair cells are solid with minor inclusions and psilate surfaces and range in length from ca. 30 to 115 Am. The apices are pointed, when not snapped off, and the hair bases are slightly bulbous and covered in short spines, either truncated, pointed or dendritic in nature. The hair bases consist of a central anchor point for the hair in the centre of seven or eight radially arranged, wedge-shaped subsidiary epidermal cells. The narrow end of each cell typically contains a dark lunate zone, perhaps representing a secondary phase of silicification providing additional support for the hair base. There seems to be little discernible difference between the phytoliths of the two species, but further detailed comparative work may highlight some diagnostic features. Both species produced psilate tracheid phytoliths and A. minor var. antarctica also produced some scalariform, or banded, tracheid phytoliths. The most productive species is A. anserinifolia consisting of 5.44% phytoliths by dry weight. Although containing similar morphotypes to A. minor var. antarctica, the latter produced only trace quantities. This difference may be related more to genetics or the age of the plants than environmental setting as the samples were both collected from Otari Botanic Gardens in Wellington. Acaena novae-zelandiae, a naturalised New Zealand native on Campbell Island was also analysed for phytolith content during this study. This species also produced distinctive polyhedral epidermal cells, nonsegmented hair cells with spinulose bulbous ends and wedge-shaped hair base subsidiary cells. Further work may distinguish species, but at this stage, the phytolith production appears similar within the Acaena genera.

Fig. 2. Common and distinctive phytolith morphotypes extracted from Campbell Island producer species. Transmitted light microscope photographs and outline sketches to indicate the variety of form within the short cell grass phytolith categories.

48

V.C. Thorn / Review of Palaeobotany and Palynology 132 (2004) 37–59

Sedge Cyperaceae, Carex trifida Cav. (1799) Vernacular: Mutton bird sedge, Tataki The Cyperaceae are commonly known as sedges (herbaceous perennials with a grass-like habit) and are widely distributed in moist habitats throughout the world. Carex trifida is a robust sedge forming dense, light green tussocks and is probably the largest of the New Zealand species (Moore and Edgar, 1976). There are 10 Cyperaceae species listed in the Campbell Island flora with four being of restricted distribution (Given and Meurk, 1980). Carex trifida is a typical (but non-constant) dominant species of maritime, megaherb-tussock grassland and sheltered-maritime Hebe elliptica-mixed tussock-scrub vegetation community types (Meurk et al., 1994). The New Zealand distribution is restricted to Banks Peninsula in South Island, New Zealand (Allan, 2000) and many of the offshore islands. Cyperaceae are known to be producers of abundant epidermal phytoliths (Metcalfe, 1971; Piperno, 1988; Kondo et al., 1994; Kealhofer and Piperno, 1998; Pearsall, 2000; Ball, 2002; Wallis, 2003). Kealhofer and Piperno (1998) also noted the presence of elongate, hair, tracheid, mesophyll and other epidermal cell phytoliths in species of Cyperus. The most common forms are often referred to as ‘hat-shaped’ or ‘conical’ and are considered diagnostic at least to family level by many researchers (Ollendorf, 1992; University of Missouri Paleoethnobotany Laboratory, 2002). However, care must be taken when applying this assumption as Hart (1990) found members of the Mimosaceae in southeastern Australia also produced similar forms. The Carex trifida analysed in this study produced abundant hat-shaped epidermal phytoliths (97%, n = 300) and rare psilate elongate, rectangular plate and globular mesophyll cell phytoliths, consistent with the previous studies on Cyperaceae (Fig. 2). The dominant form (80%) were individual, rounded, psilate cones with knobbly apices and satellites on the periphery (terminology after Ollendorf, 1992). The remaining cones were similar but paired in platelets (16%) with one specimen consisting of a platelet with four apices and associated satellites. The diameter of the individual cones averages ca. 20 Am. Metcalfe (1971) describes conical shaped phytoliths from Carex, which vary in size and shape. They

are described as being with or without satellites and can consist of 1 –7 conical bodies per cell, rarely in more than one row. Carex trifida is not described explicitly by Metcalfe (1971), however, the observed single and paired conical phytoliths observed during this study agree with these generic features. Shrub Plantaginaceae, Hebe elliptica (G. Forst) Pennell Vernacular: Shore hebe, Shore koromiko The Plantaginaceae (now including many genera that were formerly classified as Scrophulariaceae, Olmstead et al., 2001) are a large family of flowering plants consisting mostly of shrubs and herbs and distributed from high to low latitudes. The two native members of this family in the Campbell Island flora are Hebe elliptica and Hebe benthamii (Given and Meurk, 1980). H. elliptica is a constant dominant taxon in sheltered-maritime H. ellipticamixed tussock-scrub and a typical, non-constant dominant in maritime, megaherb-tussock grassland vegetation community types on Campbell Island (Meurk et al., 1994). Its New Zealand distribution is coastal, around most of South Island (except the drier eastern and northeastern shores) and rare locations up the west coast of North Island (Allan, 2000). H. benthamii is endemic to Auckland and Campbell Islands (Allan, 1961) but did not produce any phytoliths. The Hebe elliptica sample analysed in this study produced epidermal groundmass cell, spirally thickened tracheid cell and stomatal complex (guard and subsidiary cell) phytoliths (Fig. 2). The stomatal complex morphotypes were the most common and consisted of silicified guard cells—most commonly of lunate shape indicating an open stomata, held together by surrounding subsidiary cells. The longest diameter of the stomatal complex ranged from ca. 40 to 100 Am. The surface texture of the guard cells was either psilate or verrucate. The epidermal groundmass cells were psilate and polygonal with rounded corners. Grass Grasses are a prominent component of the Campbell Island flora, which includes native species of Agrostis, Chionochloa, Deschampsia, Hierochloe,

V.C. Thorn / Review of Palaeobotany and Palynology 132 (2004) 37–59

49

Lachnagrostis, Poa, Puccinellia and Trisetum, in addition to additional alien taxa (Given and Meurk, 1980). Chionochloa antarctica, Poa litorosa and an undifferentiated Poa sp. sample were analysed in the current study. Poaceae are abundant phytolith producers world-wide (e.g. Twiss et al., 1969; Piperno, 1988; Mulholland and Rapp, 1992; Twiss, 1992; Kondo et al., 1994; Pearsall, 2000). A large variety of short and long cell morphotypes (Metcalfe, 1960) is produced commonly within the same plant as well as between species. Many short cell phytoliths are diagnostic to subfamily level, despite a level of redundancy, and some Neotropical grasses to genus-level (Piperno and Pearsall, 1998). Poaceae, Chionochloa antarctica (Hook f.) Zotov (1963) Chionochloa antarctica is a constant dominant taxa in mid altitude Chionochloa-divaricating shrub – fern tussock grassland and low altitude, Chionochloa tall tussock/Dracophyllum prostrate shrub/ cushion-turf-(pillow) bog vegetation community types on Campbell Island. It is also a typical, but non-constant dominant in two other vegetation types: mid altitude Poa litorosa-Bulbinella short tussock meadow and low to mid altitude Dracophyllum meadow scrub (Meurk et al., 1994). It is endemic to Campbell and Auckland Islands (Edgar and Connor, 2000). The Chionochloa antarctica sample analysed in this study produced abundant short cell and rare elongate morphotypes (Table 2). The proportion of silica per dry weight of grass leaves was relatively low for a grass at 0.61%. The most abundant forms in a count of 300 individual phytoliths were the short cell categories ‘rondel short regular’ (53%) and ‘rondel tall irregular’ (37%) (Fig. 2). The former morphotype varies in basal diameter from ca. 15 to 25 Am and exhibits a variety of outlines, as illustrated in Fig. 3. The key characteristics were defined as a broad truncated cone shape, which was broader than it was tall, with a relatively smooth upper plateau. In contrast, the ‘rondel tall irregular’ morphotype, although also a truncated cone shape, was defined as being taller than broad, with a relatively undulose or spinulose upper plateau. These morphotypes ranged in basal diameter from ca. 10 to 12 Am. Together, all categories of rondel morphotypes totalled 93% of the

Fig. 3. Cumulative frequency curves illustrating the distribution of major phytolith morphotypes produced by the three Campbell Island grass samples: Chionochloa antarctica, Poa litorosa and Poa sp.

count. The remaining 7% consisted of saddle (3%), elongate (3%) and irregular (1%) morphotypes. Phytoliths comparable to the rondel shapes observed in this study have been recognised relatively recently in tropical soils (Pearsall, 2000) and in New Zealand grasses Chionochloa and Cortaderia (Kondo et al., 1994). Poaceae, Poa litorosa Cheeseman (1906) and Poa sp. Poa litorosa is common in many habitats on Campbell Island, being a constant dominant taxa in eight different vegetation community types and a typical, non-constant dominant in a further five. These community types range from maritime grasslands to low to mid altitude herbfields, grasslands, swamps and shrublands (Meurk et al., 1994). This species is endemic to several subantarctic islands, including Auckland and Campbell Islands, the Antipodes and Macquarie Island (Edgar and Connor, 2000). The sample of Poa litorosa analysed in this study produced both short and long cell phytoliths (Table 2). The proportion of silica per dry weight of grass leaves was 2.29%. The most abundant forms observed during a 300 count were elongates with a psilate surface

50

Phytolith morphotypes

Anisotome Pleurophyllum Anisotome Stilbocarpa Poa antipoda speciosum latifolia polaris sp.

Collection localitya

a

% Total biogenic silica by dry weightb

1.29

4.15

1.23

7.80

7

22 13 6 15 1 25 46

3 6 6 29

12

Grass morphotypes Bilobate Narrow base Wide base Polylobate Sinuate Trilobate Rondel

Short

Tall

Saddle

Narrow base Wide base

Sedge morphotype Hat-shaped Tree/Shrub morphotypes Spherical Irregular Multifaceted

Regular Irregular Regular Irregular Irregular Keeled Regular Conical Irregular Narrow Pointed Regular

b

1 14 2 5 54 3 21

4 53 4 20

2.18 trace 24

1.61

3.51

2.39

trace

10

4 13

10

2

18

72

71 4 105

32

4 1 2 3 6 79 4 1

5

98

6 49 1 47 5 61

16 9 11

21 60

18

6

1

2

7 30

17 6

95

23 1 45

8 22 59

9 82

1 27 50

38

8 86 21

2

2

3

17

1

4

60

Bulbinella Pleurophyllum Pleurophyllum Chionochloa Dracophyllum Myrsine Main rossii criniferum hookeri antarctica spp. divaricata phytolith sum c d e f g

1 12

9 6 39 5 32 1 75

136 1 54

1 39 60

51 30

8 1 59

0.65

10 4 11 8 36 9

15

94 46 26 147 12 61 505 26 398 12 686

62

26

13

5

5 6

1

65

153

266

2

8 2

52 264 417 6

V.C. Thorn / Review of Palaeobotany and Palynology 132 (2004) 37–59

Table 3 Campbell Island modern soil surface samples. Collected beneath stated plants

Smooth

Psilate Pitted

1

Miscellaneous dicotyledon morphotypes Plate Irregular Polygonal Regular Irregular Rectangular

1 1

1

2

1

1 3

1

1

1

3

1 9

1

2

4

Miscellaneous dicotyledon (angiosperm)/fern/grass morphotype Anticlinal Spinulose Unknown origin Irregular Multifaceted Opaque Non-opaque Spinulose Elongate Dendritic Psilate Spinulose Undulose Total specimens a

5 11 3 2

1 1 1

2

4

1

8

1 5

2

8

2 1

3

3 7 1 3 302

Refer to Fig. 1. b Includes diatoms and other soil biogenic silica.

7 2 305

2 14 2

1 2

299

294

3 8 306

23 7 3 300

18 5 2 300

3 14 7

6 1

5

44 7

17 6

300

303

300

303

21 3 9 3 2 145 31 18 3312

V.C. Thorn / Review of Palaeobotany and Palynology 132 (2004) 37–59

Miscellaneous grass/sedge/dicotyledon morphotypes Trichome Hair base Hair Hollow Solid

5 7

1

4 1

51

52

V.C. Thorn / Review of Palaeobotany and Palynology 132 (2004) 37–59

texture (38%) and narrow based saddles (35%) (Fig. 3). The elongate morphotypes were commonly >100 Am in length (probably limited by the processing procedure) and the saddles longest dimension ca. 15 Am. Additional relatively prevalent morphotypes were tall conical (11%) and irregular (10%, Fig. 2) rondels. Other morphotypes included short irregular rondel (2%), pointed tall rondel (3%) and elongate (1%) morphotypes. A further Poa sample was analysed of an unidentified species. This grass had a phytolith assemblage quite different to Poa litorosa with predominantly tall, irregular rondels (63%, n = 300) and polylobate (26%) morphotypes. Other morphotypes observed were tall pointed rondels (5%), trichome hair cell and bases (4%) and elongates (2%). This Poa sp. had a slightly lower silica content per dry weight than the P. litorosa sample at 1.40%. However, differing environmental factors between the collection sites at Invercargill and Campbell Island may have affected phytolith production within members of this genus. Comparing the cumulative frequency distributions of the major phytolith categories using the non-parametric, two-sample Kolmogorov-Smirnov test (Fig. 3), it is interesting to note a significant difference at the 95% confidence level (n = 10) between the Poa sp. and the Poa litorosa samples, but no significant difference between either of the Poa spp. and the Chionochloa antarctica assemblages. This suggests that there is little difference in major morphotypes between the Poa and Chionochloa, but that there may be variation within the Poa at the generic level. This result also questions the reliability of the initial generic identification of the Poa sp. sample, and can only be resolved by further collection. 4.2. Soil surface phytolith spectra All 11 soil surface samples collected from Campbell Island contained abundant and diverse phytoliths (Table 3). The phytoliths are well preserved, indicating a lack of dissolution in the soil or physical abrasion during entrainment. The total biogenic silica content of the samples ranged from trace quantities to 7.8% of dried material. Significantly, nine samples consisted of between 78% and 97% grass morphotypes (predominantly short cells). The remaining

Dracophyllum spp. and Myrsine divaricata soil surface samples contained a relatively high percentage (22% and 51%, respectively) of sedge hat-shaped phytoliths. The Dracophyllum spp. sample also contained 15% of psilate elongate forms, which are currently of unknown origin. A comparison of phytolith morphotypes extracted from the plants and the soil surface samples indicates there are 22 morphotypes occurring in both (grass, sedge and miscellaneous trichome, irregular and elongate morphotypes) and others that only occur in either the plants or the soil surface. Additional morphotypes in the soil surface samples not observed in the plants processed are low numbers of spherical morphotypes (generally characteristic of trees and/or shrubs), plates and anticlinal morphotypes (miscellaneous dicotyledon forms). The low stature Campbell Island vegetation includes only a few woody shrubs and low trees up to 4 m tall (Dracophyllum, Coprosma, Hebe and Myrsine species, plus Calluna vulgaris (introduced heather)). None of the sampled native species from this group that have been processed during this study produced spherical phytoliths. C. vulgaris, a persistent alien on Campbell Island, is known to produce abundant biogenic silica in its leaves although no spherical morphotypes have been described (Carnelli et al., 2001, 2004). This suggests that non-woody components of the flora, yet to be analysed, may be the source of these forms found in the soil surface assemblages. Thin-walled epidermal (including guard cells) and mesophyll cell linings, and both psilate and ornamented tracheid linings were observed in several plants processed, but were not observed in the soil surface samples. At localities a, b and c (Fig. 1), soil surface samples were collected beneath more than one plant (Table 3) to test the level of variability between soil surface phytolith assemblages collected in close proximity. The cumulative frequency distributions of the soil surface assemblages at each of these sites are plotted in Fig. 4. Using the Kolmogorov-Smirnov test, there is no significant difference (at the 95% level, n = 13) between the assemblages collected within each site. The similarity between these multiple samples allows them to be homogenised or averaged per site to allow comparisons between localities. Cumulative frequency distributions of the major phytolith morphotypes encountered in the soil surface

V.C. Thorn / Review of Palaeobotany and Palynology 132 (2004) 37–59

53

Fig. 5. Cumulative frequency curves illustrating the percentage of major phytolith morphotypes within soil surface samples collected from Campbell Island, plotted by collection locality. For specific sample localities refer to Fig. 1 and Table 3.

samples are plotted in Fig. 5. The KolmogorovSmirnov test results (at the 95% level, n = 13) suggest that there is no significant difference between the assemblages observed at localities a – f. However, the assemblages from a to e are all significantly different to that at locality g. The locality c assemblage shows slightly more similarity to that at locality g being significantly different only at the 90% level.

5. Discussion The differences between the phytoliths observed in the plants analysed and the soil surface assemblages from Campbell Island essentially resolve into the dominance of graminoid phytolith production and primarily grass phytolith survival once entrained into the soil. The observation of certain morphotypes in the soil surface assemblages not seen in the plants Fig. 4. Cumulative frequency curves illustrating the percentage of major phytolith morphotypes within soil surface samples collected from three localities on Campbell Island (refer to Fig. 1 and Table 3). (a) Samples from locality a; (b) Samples from locality b; (c) Samples from locality c.

54

V.C. Thorn / Review of Palaeobotany and Palynology 132 (2004) 37–59

analysed, is most likely due to an incomplete modern reference collection as no source from the island flora is yet known for the rare spherical morphotypes typically produced by trees or shrubs. Due to the issues of phytolith multiplicity and redundancy it may never be possible to confidently relate all phytolith morphotypes observed in a dispersed assemblage to specific taxa, even within a restricted flora on a geographically isolated island, which effectively precludes ‘contamination’ from other flora. Conversely, the thin-walled cell lining and tracheid phytoliths observed in several of the plants analysed, but not in the soil surface assemblages suggests that these taxa may not have been growing in the vicinity of the collection localities or have not been preserved due to dissolution or physical fragmentation. The forbs and Hebe elliptica, which produced these fragile morphotypes, were extracted from plants collected in New Zealand. However, we can assume similar silicification patterns between individuals of the same species, despite their physical location, depending on adequate dissolved silica in the groundwater, which is evident on Campbell Island due to the abundant phytolith production from the grasses analysed. The generalised composition of the vegetation community types at the collection sites on Campbell Island (Meurk et al., 1994) suggests that of these taxa, only H. elliptica is likely to have been growing at one of the localities (locality g). Therefore, it is likely that these taxa were not growing sufficiently close to the soil surface collection localities to survive the entrainment process and contribute to the phytolith assemblage. The high proportion of diverse grass short cell phytoliths in the soil surface assemblages implies that phytolith entrainment into the soil is not only through direct in situ deposition by a decomposing plant at the growth site, but grasses surrounding the collection localities are contributing to the accumulation, as only two of the soil surface samples were collected directly beneath individual grass plants (Poa sp. and Chionochloa antarctica). This suggests there is local or extra-local transport of phytoliths in this environment, possibly in the form of surface runoff over the saturated peat, mass movements of the peat or wind transport. Further, the similarity of the soil assemblages from localities a –f, assessed with the Kolmogorov-Smirnov test, reflects the widespread distribution of grasses in the Campbell Island

vegetation (Given and Meurk, 1980; Meurk et al., 1994), particularly Poa litorosa and C. antarctica in the vegetation CTs surrounding the collection localities. The predominance of grass phytoliths also demonstrates the low proportion of non-grass phytolith producing taxa contributing to the accumulation of biogenic silica in the soil. This, and the suggested transport mechanisms above, have the effect of mixing the dominantly grass phytoliths produced in the area and effectively homogenising the content of the soil surface phytolith spectra, which implies it is not yet possible to differentiate between different overlying vegetation community types from the dispersed assemblages. Locality g at sea level, is the furthest east of the collection localities and has a significantly different soil surface assemblage to all other localities except f. It is geographically closest to localities c and f, at f 50 and f 70 masl, respectively. The assemblages from localities f and g both have relatively high proportions of sedge phytoliths compared to the other localities (Table 3), suggesting a localised dominance of these plants. Locality g is located within vegetation CT Pm (Meurk and Given, 1990), equivalent to CT 19 in Meurk et al. (1994). The sedge, Carex trifida, is a typical, but non constant dominant in this shelteredmaritime Hebe elliptica-mixed tussock-scrub community and is therefore the likely source of the high proportion of sedge hat-shaped phytoliths in the soil surface assemblage. Locality f is within CT Df (Meurk and Given, 1990), which contains taxa equivalent to CTs 19 and 20 in Meurk et al. (1994) implying a similar source of sedge phytoliths, despite a higher altitude and different vegetation CT. The soil assemblage at locality f appears to be intermediate between localities a– e and locality g as it remains similar to the former and the latter, despite the significant differences between the assemblages at localities a –e and g. A pollen rain study on Campbell Island (McGlone and Meurk, 2000) encountered 44 indigenous spore and pollen types, of which 19 were identifiable to species. Despite the differences in modes of transport and entrainment, comparable to the dominance of grass phytoliths in the soil surface, total Poaceae pollen percentages were the highest of all the palynomorphs observed in the pollen rain (in similar abundances to Polystichum), which is considered to

V.C. Thorn / Review of Palaeobotany and Palynology 132 (2004) 37–59

mainly represent the abundance of Poa spp. However, in contrast to the phytolith production, pollen from shrub taxa was found to be generally widespread, except for Hebe spp., which had typically poor pollen representation. If soil conditions were sufficiently stable for the silicified stomatal phytoliths to preserve, as extracted from Hebe elliptica during this study, then the soil surface phytolith record would supplement the terrestrial palynomorph interpretation of the source vegetation. Similarly, despite the apparent similarity in phytolith morphotypes produced by both the Poa litorosa and Chionochloa antarctica grass samples, the diversity and abundance of morphotypes therein suggests there remains potential, with further detailed taxonomic analysis, for differentiating the grass genera based on phytolith content. Differentiating between dispersed grass pollen is a difficult issue in terrestrial palynology, hence only broad reconstructions of the grass component of a vegetation community are possible using this technique alone. Both the pollen and phytolith soil surface records suggest a relationship between the abundance of sedge-type phytoliths or pollen and the abundance of sedge (Carex) taxa in the surrounding vegetation. Therefore, with further development of the phytolith analysis technique, particularly with regard to reference material, dispersed phytolith assemblages in the soil or peat have the potential to contribute significantly to the reconstruction of past vegetation on Campbell Island in a similar manner to that of terrestrial palynology. At this stage, the pollen rain provides additional taxonomic information about the source vegetation beyond the phytolith record, particularly on the macrophyllous forb and fern components of the vegetation as analysed samples from these plant groups did not produce phytoliths. Assessment of the accuracy of vegetation reconstructions from fossil phytolith assemblages is important when employing the ‘Nearest Modern Relative’ technique to make extrapolations into the past about the possible nature of the regional climate around the study site. If key components of the vegetation are missing from the interpretation due to an incomplete or poorly understood fossil record, then the resulting climate interpretation will be inaccurate and the technique rendered invalid. Therefore, the importance of continuing modern phytolith production surveys and assessing entrainment into and subsequent preserva-

55

tion in soil and ultimately offshore sediment is paramount to the application of phytolith analysis to palaeoenvironmental investigations within and beyond the subantarctic region. Despite the limited scope of this study, it is useful to make an initial comparison with the fossil phytolith assemblage previously described from Oligocene and Miocene seafloor sediments off the Antarctic margin. Palaeobotanical evidence from the margin of the Antarctic ice sheet during the Tertiary is sparse (e.g. Mildenhall, 1989; Truswell and Barron, 1991; Raine, 1998; Askin, 2000; Askin and Raine, 2000; Raine and Askin, 2001; MacPhail and Truswell, 2004). However, it is of substantial interest to the investigation of the development of the East Antarctic Ice Sheet during the Oligocene and Miocene. At this time, temperatures in the Ross Sea region were significantly warmer than today with a mean summer monthly temperature of ca. 12 jC, 34 –25 Ma and 5– 7 jC, 24 –17 Ma (Raine and Askin, 2001) compared to 5 jC at the present day. The phytoliths described from the CRP-2/2A and CRP-3 Cape Roberts Project (CRP) cores from the Ross Sea region of Antarctica were dominantly spherical forms (Thorn, 2001) with diverse surface ornamentation. Rare grass morphotypes were also present. Five broad morphotype categories (elongate, polylobate (or ‘festucoid’, as referred to in Thorn, 2001), bilobate (or ‘panicoid’), tracheid and mesophyll (or ‘tissue’)) described from the modern subantarctic plants analysed in this study are also represented in the CRP flora. Unfortunately, apart from a broad similarity in morphology, they cannot be directly compared and provide no extra taxonomic information to aid the interpretation of the fossil assemblage. The shrubs analysed from the Campbell Island flora (Dracophyllum spp., Hebe spp., Myrsine divaricata and Coprosma sp.) were either non-phytolith producers or produced thin-walled forms that it is unlikely would survive in the fossil record. Essentially, the broadly grass dominated modern phytolith production evident on subantarctic Campbell Island represents a different assemblage from the tree/shrub dominated Oligocene/Miocene Antarctic margin assemblage. The Oligocene terrestrial palynology from the Cape Roberts Project cores (Askin and Raine, 2000;

56

V.C. Thorn / Review of Palaeobotany and Palynology 132 (2004) 37–59

Raine and Askin, 2000, 2001) differs from the Holocene peat palynoflora and modern pollen rain described from Campbell Island (McGlone et al., 1997; McGlone and Meurk, 2000) despite certain comparable palynomorphs and inferred similar prevailing climatic conditions. The pre-Quaternary palynoflora of Campbell Island is currently almost unknown, although Fleming (1978) described lignites containing abundant plant microfossils (including Nothofagus) in the Pliocene East Coast Volcanic Formation. Palynofloras from both the Cape Roberts cores and the Campbell Island records include bryophyte, lycopod, possible Cyperaceae and fern representatives. The terrestrial palynoflora of the lowermost CRP-2/2A and upper CRP-3 core sections, correlated with the early Oligocene, is dominated by contemporaneous Nothofagidites spp. and includes several Podocarpidites species (Raine and Askin, 2001). The prevalence of these pollen types is considered to represent a contemporaneous woody vegetation in the Transantarctic Mountains onshore of the drill-site. In contrast, Nothofagus fusca type, Nothofagus menziesii and several podocarp pollen types occur only rarely in the Holocene Campbell Island peat record and modern pollen rain as exotics blown in from the New Zealand mainland (McGlone et al., 1997; McGlone and Meurk, 2000). In addition, possible Caryophyllaceae pollen is noted in the CRP flora and rare Colobanthus pollen occurs in the Campbell Island modern pollen rain. Despite these similarities, the palynofloras are quite different due to the dominance of Nothofagidites and podocarp types in the CRP flora, representing a regionally proximal woody vegetation, and the rare occurrence of both these pollen types in the Campbell Island records as long-distance windblown components. The Early Oligocene CRP flora is interpreted to represent a low diversity woody vegetation, including a few cryptogams, with minor wetland and favourable sites containing low scrub or closed forest. A transition occurred with cooling temperatures into the Early Miocene implying the growth of a tundra-like parent vegetation with Nothofagus scrub, a few other angiosperms, podocarps and bryophytes. The timing of the final demise of this sparse vegetation remains unclear, but it would have succumbed to the enlarging ice sheet between ca. 15 and 3 Ma (Raine and Askin, 2001).

The climatic conditions inferred for the Ross Sea margin in the Cape Roberts region during the Oligocene and Early Miocene compare well to the modern prevailing climatic conditions at Campbell Island. However, the differences in the vegetation composition, using both phytolith and terrestrial palynomorph interpretations are significant. The reason for these differences are still to be fully investigated, but may include evolution to cope with different growth environments, for example, Campbell Island is extremely oceanic compared to a mountainous coastal margin. Further, elements of the vegetation may have been sourced from different continents, for example, Antarctica (prior to ice sheet development), Australia, or New Zealand. In this context, the current study begins what may become a substantial contribution from the phytolith record to knowledge about the origin and history of the former land vegetation (and consequently climate) of Antarctica as the New Zealand subantarctic islands flora include some taxa with circumpolar and australalpine distribution (J.I. Raine, personal communication, 2003).

6. Conclusions This study is the first to describe phytoliths from the New Zealand subantarctic islands and forms the beginning of a modern reference collection from this region. The graminoids (grasses (Chionochloa antarctica, Poa litorosa and Poa sp.) and sedge (Carex trifida)) analysed from the Campbell Island flora all contained abundant, robust phytoliths, the former producing predominantly short cells (bilobate, rondel and saddle morphotypes) and the latter distinctive hat-shaped morphotypes common in the Cyperaceae. Several forbs (Acaena anserinifolia, Acaena minor var. antarctica, Myosotis capitata, Anaphalioides bellidioides) and one shrub (Hebe elliptica) also produced phytoliths, but generally only thin-walled forms that were not observed in the soil surface assemblages, perhaps due to the lack of proximity to the collection locality or soil dissolution. The analysis of many dominant taxa from the Campbell Island vegetation suggests that the majority of phytolith production occurs within the graminoids. This is reflected in the analysis of soil surface

V.C. Thorn / Review of Palaeobotany and Palynology 132 (2004) 37–59

samples from a central part of the island, which are dominated by grass phytoliths. The only significantly different assemblage contained a high proportion of sedge phytoliths and was from a site near sea level within a vegetation community containing C. trifida as a typical, but non constant dominant taxa. Therefore, with current phytolith production knowledge of the Campbell Island flora, it is not yet possible to differentiate between different vegetation community types on the basis of the underlying soil surface assemblages. In order to develop this concept an extended plant reference collection is required in order to better understand the phytolith production patterns within the flora. Further, a quantitative method of surveying the proportions of each taxa growing over a soil surface collection site would provide insight into the representativeness of the soil surface phytolith assemblage of the overlying vegetation, in a similar manner to that undertaken for a previous study of the pollen rain on Campbell Island (McGlone and Meurk, 2000). An attempt was made to apply the draft ICPN (Madella et al., 2003) to classify the phytoliths observed during this study. However, difficulties encountered applying adequate descriptors to differentiate certain morphotypes precluded its adoption for this study. The phytolith morphotypes extracted from plants analysed in this study differ from types extracted from the Oligocene and Miocene CRP seafloor sediment cores from the Ross Sea region of Antarctica. The CRP phytolith flora consists of dominantly tree/shrub spherical morphotypes, in contrast to the grass short cell-dominated assemblages of Campbell Island. This highlights the need for an extended subantarctic phytolith reference database to provide modern analogues necessary for vegetation and climate reconstruction from Antarctic margin phytolith flora during the critical period of Oligocene and Miocene ice sheet development.

Acknowledgements This study was supported by a New Zealand Foundation for Research, Science and Technology Post-Doctoral Fellowship. The author would like to thank John Carter, Phil Garnock-Jones, Fanie Ventner and Peter Barrett (Victoria University of Wellington,

57

NZ), Carol West (NZ Department of Conservation), Eleanor Burton (Otari Botanic Gardens, Wellingtonn) and Keith Dudfield and Claire Walkinshaw (Invercargill City Council, NZ) for their various contributions to this project.

References Allan, H.H., 1961. Flora of New Zealand. In: Hasselberg, P.D. (Ed.), Volume I, Indigenous Tracheophyta-Psilopsida, Lycopsida, Filicopsida, Gymnospermae, Dicotyledones. Government Printer, Wellington, New Zealand, p. 1. Allan, H., 2000. New Zealand Plant Names Database. Landcare Research, New Zealand. Available at http://nzflora. landcareresearch.co.nz/ (Accessed June 16, 2003). Arand, J., Basher, L., McIntosh, P., Heads, M., 1991. Inventory of New Zealand soil sites of international, national and regional importance. Part 1—South Island and Southern Offshore Islands. New Zealand Society of Soil Sciences Occasional Publication, vol. 1. Christchurch, Christchurch, New Zealand, p. 127. Askin, R.A., 2000. Spores and pollen from the McMurdo Sound Erratics, East Antarctica. In: Stilwell, J.D., Feldmann, R.M. (Eds.), Paleobiology and Paleoenvironments of Eocene rocks, McMurdo Sound, Antarctica. Antarctic Research Series. American Geophysical Union, Washington, DC, pp. 161 – 181. Askin, R.A., Raine, J.I., 2000. Oligocene and Early Miocene terrestrial palynology of the Cape Roberts drillhole CRP-2/2A, Victoria Land Basin, Antarctica. Terra Antart. 7 (4), 493 – 501. Baker, G., 1959. Opal phytoliths in some Victorian soils and ‘red rain’ residues. Aust. J. Bot. 7, 64 – 87. Ball, T., 2002. Dhofar phytoliths. Unpublished. CD-ROM. Bowdery, D., 1999. Taphonomy, phytoliths and the African Dust Plume. In: Mountain, M. (Ed.), Taphonomy: The Analysis of Processes from Phytoliths to Megafauna. Research Papers in Archaeology and Natural History. ANH Publications, ANU, Canberra, pp. 3 – 8. Bowdery, D., Hark, D., Lenkfer, C., Wallis, L., 2001. A universal phytolith key. In: Meunier, J., Fabrice, C., (Eds.), Phytoliths: Applications in Earth Sciences and Human History. A.A. Balkema, Lisse, pp. 267 – 278. Bozarth, S.R., 1992. Classification of opal phytoliths formed in selected dicotyledons native to the Great Plains. In: Rapp Jr., G., Mulholland, S.C. (Eds.), Phytolith Systematics—Emerging Issues. Advances in Archaeological and Museum Science. Plenum, New York, pp. 193 – 214. Brown, D.A., 1984. Prospects and limits of a phytolith key for grasses in the central United States. J. Archaeol. Sci. 11, 345 – 368. Campbell, I.B., 1980. Soil pattern of Campbell Island. N. Z. J. Sci. 24, 111 – 135. Carnelli, A., Madella, M., Theurillat, J.P., 2001. Biogenic silica production in selected alpine plant species and plant communities. Ann. Bot. 87 (4), 425 – 434.

58

V.C. Thorn / Review of Palaeobotany and Palynology 132 (2004) 37–59

Carnelli, A., Theurillat, J.-P., Madella, M., 2004. Phytolith types and type-frequencies in subalpine-alpine plant species of the European Alps. Rev. Palaeobot. Palynol. 129, 39 – 65. Carter, J.A., 1998. Phytoliths from CRP-1. Terra Antart. 5 (3), 571 – 576. Cockayne, L., 1904. A botanical excursion during midwinter to the southern islands of New Zealand. Trans. Proc. R. N. Z. Inst. 36, 225 – 333. Cockayne, L., 1909. The ecological botany of the subantarctic islands of New Zealand. In: Chilton, C. (Ed.), The Subantarctic Islands of New Zealand. Government Printer, Wellington, New Zealand, pp. 182 – 235. De Lisle, J.F., 1965. The climate of the Auckland Islands, Campbell Island and Macquarie Island. Proc. N. Z. Ecol. Soc. 12, 37 – 44. Edgar, E., Connor, H.E., 2000. Flora of New Zealand-Volume V: Gramineae. Manaaki Whenua Press, Lincoln, New Zealand, p. 5. Fleming, C.A., 1978. Tertiary: stratigraphy: Campbell and Auckland Islands. In: Suggate, R.P., Stevens, G.R., Te Punga, M.T. (Eds.), The Geology of New Zealand. Government Printer, Wellington, pp. 532 – 533. Fredlund, G.G., Tieszen, L.T., 1994. Modern phytolith assemblages from the North American Great Plains. J. Biogeogr. 21, 321 – 335. Geis, J.W., 1973. Biogenic silica in selected species of deciduous angiosperms. Soil Sci. 116 (2), 113 – 130. Given, D.R., Meurk, C.D., 1980. Checklist of the vascular flora. Preliminary Reports of the Campbell Island Expedition 1975 – 76. Reserves Series, vol. 7. Department of Lands and Survey, Wellington, New Zealand, pp. 83 – 87. Gobetz, K.E., Bozarth, S.R., 2001. Implications for Late Pleistocene Mastodon Diet from Opal Phytoliths in Tooth Calculus. Quat. Res. 55, 115 – 122. Hart, D.M., 1990. Occurrence of the ‘Cyperaceae-type’ phytolith in dicotyledons. Aust. Syst. Bot. 3, 745 – 750. Hart, D.M., 1997. Phytoliths and fire in the Sydney Basin, New South Wales, Australia. In: Pinilla, A., Juan-Tresseras, J., Machado, M.J. (Eds.), First European Meeting on Phytolith Research. Monografias del Centro de Ciencias Medioambientales. Centro de Ciencias Medioambientales del Consejo Superior de Investigaciones Cientificas, Madrid, pp. 101 – 110. Kealhofer, L., 1998. A combined pollen and phytolith record for fourteen thousand years of vegetation change in northeastern Thailand. Rev. Palaeobot. Palynol. 103, 83 – 93. Kealhofer, L., Piperno, D.R., 1998. Opal phytoliths in Southeast Asian flora. Smithsonian Conkril. Bot., p. 88. Kondo, R., Childs, C., Atkinson, I., 1994. Opal Phytoliths of New Zealand. Manaaki Whenua Press, Lincoln. MacPhail, M.K., Truswell, E.M., 2004. Palynology of Neogene slope and rise deposits from ODP Sites 1165 and 1167, East Antarctica. In: Cooper, A.K., O’Brien, P.E., Richter, C. (Eds.), Proc. ODP, Sci. Results, 188 [Online]. Available http://wwwodp.tamu.edu/publications/188_SR/012/012.htm Madella, M., Alexandre, A., Ball, T., 2003. International Code for Phytolith Nomenclature 1.0. Phytolitharien 15 (1), 7 – 16. McGlone, M.S., 2002. The late Quaternary peat, vegetation and climate history of the Southern Oceanic Islands of New Zealand. Quat. Sci. Rev. 21, 683 – 707. McGlone, M.S., Meurk, C.D., 2000. Modern pollen rain, subant-

arctic Campbell Island, New Zealand. N. Z. J. Ecol. 24 (2), 181 – 194. McGlone, M.S., Wardle, P., Meurk, C.D., 1997. Late-glacial and Holocene vegetation and environment of Campbell Island, far southern New Zealand. Holocene 7, 1 – 12. Metcalfe, C.R., 1960. Anatomy of the Monocotyledons: Gramineae, vol. 1. Clarendon Press, Oxford. Metcalfe, C.R., 1971. Anatomy of the Monocotyledons: Cyperaceae, vol. 5. Clarendon Press, Oxford. Metcalfe, C.R., Chalk, L., 1983. Anatomy of the Dicotyledons: II. Wood Structure and Conclusion of the General Introduction. Clarendon Press, Oxford, p. 297. Meurk, C.D., 1975. Contributions to the flora and plant ecology of Campbell Island. N. Z. J. Bot. 13, 721 – 742. Meurk, C.D., 1980. Plant ecology of Campbell Island. Preliminary Reports of the Campbell Island Expedition 1975 – 76. Reserves Series, vol. 7. Department of Lands and Survey, Wellington, New Zealand, pp. 88 – 97. Meurk, C.D., Given, D.R., 1990. Vegetation Map of Campbell Island. DSIR Land Resources, Christchurch, New Zealand. Meurk, C.D., Foggo, N.M., Bastow Wilson, J., 1994. The vegetation of subantarctic Campbell Island. N. Z. J. Ecol. 18, 123. Mildenhall, D.C., 1989. Palaeontology—Terrestrial palynology. In: Barrett, P.J. (Ed.), Antarctic Cenozoic History From the CIROS1 Drillhole, McMurdo Sound. DSIR Bull., pp. 119 – 127. Molloy, L., 1998. Soils in the New Zealand Landscape—the Living Mantle. New Zealand Society of Soil Science, Lincoln. Moore, L.B., Edgar, E., 1976. Flora of New Zealand. Indigenous Tracheophyta—Monocotyledones Except Gramineae, vol. 2. Government Printer, Wellington, pp. 269 – 270. Mulholland, S.C., Rapp, G.J., 1992. A morphological classification of grass silica-bodies. In: Rapp Jr., G., Mulholland, S.C. (Eds.), Phytolith Systematics: Emerging Issues. Advances in Archaeological and Museum Science. Plenum, New York, pp. 65 – 90. New Zealand Meteorological Service, 1973. Summaries of climatological observations to 1970. N. Z. Meteorol. Serv. Misc. Publ. vol. 143. Government Printer Wellington, NZ, p. 77. Oliver, R.L., Sorensen, J.H., 1951. Botanical investigations on Campbell Island—the Vegetation. Cape Exped. Ser. Bull. 7 (1), 5 – 24. Ollendorf, A.L., 1992. Towards a classification scheme of sedge (Cyperaceae) phytoliths. In: Rapp Jr., G., Mulholland, S.C. (Eds.), Phytolith Systematics—Emerging Issues. Plenum, New York, pp. 91 – 111. Olmstead, R.G., dePamhilis, C.W., Wolfe, A.D., Young, N.D., Elisons, W.J. Reeves, P.A., 2001. Disintegration of the Scrophulariaceae. Am. J. Bot. 88 (2), 348 – 361. Pearsall, D.M., 1992. Developing a phytolith classification system. In: Rapp, G., Mulholland, S.C. (Eds.), Phytolith Systematics— Emerging Issues. Plenum, New York, pp. 37 – 64. Pearsall, D.M., 2000. Paleoethnobotany—a Handbook of Procedures. Academic Press, San Diego. Piperno, D.R., 1985. Phytolith analysis and tropical paleo-ecology: production and taxonomic significance of siliceous forms in New World plant domesticates and wild species. Rev. Palaeobot. Palynol. 45, 185 – 228. Piperno, D.R., 1988. Phytolith Analysis, An Archaeological and Geological Perspective. Academic Press, London, 280 pp.

V.C. Thorn / Review of Palaeobotany and Palynology 132 (2004) 37–59 Piperno, D.R., Pearsall, D.M., 1998. The silica bodies of tropical American grasses: morphology, taxonomy, and implications for grass systematics and fossil phytolith identification. Smithson. Contrib. Bot., p. 85. Piperno, D.R., Pearsall, D.M., Benfer, R.A., Kealhofer, L., Zhao, Z., Jiang, Q., 1999. Phytolith morphology. Science 283, 1265 – 1266. Raine, J.I., 1998. Terrestrial palynomorphs from Cape Roberts Project drillhole CRP-1, Ross Sea, Antarctica. Terra Antart. 5 (3), 539 – 548. Raine, J.I., Askin, R.A., 2000. Terrestrial palynology: age and paleoenvironmental results from CRP-3. In: Webb, P.N., Everett, L. (Eds.), Cape Roberts Project Workshop, Program and Abstracts for a Workshop Convened During 5 – 10 September 2000. Byrd Polar Research Center, The Ohio State University, Columbus, OH, p. 21. Raine, J.I., Askin, R.A., 2001. Terrestrial palynology of Cape Roberts Project drillhole CRP-3, Victoria Land Basin, Antarctica. Terra Antart. 8 (4), 389 – 400. Romero, O.E., 1999. Eolian-transported freshwater diatoms and phytoliths across the equatorial Atlantic record: temporal changes in Saharan dust transport patterns. J. Geophys. Res. 104 (C2), 3211 – 3222. Rovner, I., 1971. Potential of opal phytoliths for use in paleoecological reconstruction. Quat. Res. 1, 343 – 359.

59

Runge, F., 1996. Leaf phytoliths and silica skeletons from East African plants. Physical Geography, University of Pa¨derborn, Germany. CD-ROM. Thorn, V.C., 2001. Oligocene and early Miocene phytoliths from CRP-2/2A and CRP-3, Victoria Land Basin, Antarctica. Terra Antart. 8 (4), 407 – 422. Truswell, E.M., Barron, J., 1991. Data report: Palynology of sediments from Leg 119 drill sites in Prydz Bay, East Antarctica. Ocean Drill. Program Proc. Sci. Results 119, 941 – 945. Twiss, P.C., 1992. Predicted world distribution of C3 and C4 grass phytoliths. In: Rapp Jr., G., Mulholland, S.C. (Eds.), Phytolith Systematics—Emerging Issues. Plenum, New York, pp. 113 – 128. Twiss, P.C., Suess, E., Smith, R.M., 1969. Morphological classification of grass phytoliths. Soil Sci. Soc. Am. Proc. 33, 109 – 115. University of Missouri Paleoethnobotany Laboratory, 2002. Phytolith Database. University of Missouri. Available http://www.missouri.edu/phyto/index.shtml (Accessed June 16, 2003). Wallis, L.A., 2003. An overview of leaf phytolith production patterns in selected northwest Australian flora. Rev. Palaeobot. Palynol. 125, 201 – 248. Weatherhead, A.V., 1988. The Occurrence of Plant Opal in New Zealand Soils, vol. 108. New Zealand Soil Bureau, Department of Scientific and Industrial Research, Lower Hutt.