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Quaternary beetle research: the state of the art
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Quaternary beetle research: the state of the art Scott A. Elias Geography Department, Royal Holloway, University of London, Egham, Surrey TW20 0EX, UK Received 6 October 2005; accepted 11 May 2006
Abstract Quaternary beetle research has progressed in a variety of ways during the last decade. New kinds of data are being extracted from the fossil specimens themselves, such as ancient DNA and stable isotopes. The ancient DNA studies hold the promise of proving new insights on the stability of beetle genotypes. The study of stable isotopes of H and O from fossil beetle chitin holds the promise of providing an independent proxy for the reconstruction of temperature and precipitation. The discipline is also expanding into previously unstudied regions, such as Australia, New Zealand, and northern Asia. Along with the new study regions, new schools of thought are also forming in the discipline, challenging old research paradigms. This is a necessary step forward for the discipline, as it grows and develops in the 21st Century. r 2006 Elsevier Ltd. All rights reserved.
1. Introduction When ‘Quaternary Insects and Their Environments’ was published in 1994, most of the research in this field was being done either in Western Europe or in North America. I noted in that book that ‘Many of these researchers have been trained by Russell Coope at the University of Birmingham, or by his former students.’ While most of the same researchers are still active, a number of new paleoentomologists have begun publishing in this field, studying the faunas of new regions. As shown in Fig. 1, the geographic spread of research in Quaternary beetle assemblages now extends to Japan, Australia, and New Zealand. New regions of northern and central Siberia are now being investigated, as are regions in Kazakhstan. As might be expected, the people investigating Quaternary beetle assemblages in these various regions have employed new and different methods of faunal extraction, identification, and interpretation. Because of political and linguistic barriers, some Japanese and Russian researchers were only vaguely aware of the Western European and North American literature in this field when they started out. Some of their indigenous methods are quite distinct from those of Coope and his students, as will Tel.: +44 1784 443647; fax: +44 1784 472836.
E-mail address: [email protected]. 0277-3791/$ - see front matter r 2006 Elsevier Ltd. All rights reserved. doi:10.1016/j.quascirev.2006.05.002
be discussed, below. As this line of research has expanded into new regions, it has also contracted in others. Sadly, research in South America has waned since the publications by Ashworth and others in the 1980s and early 1990s. 2. General advances since 1994 Progress has been achieved along a number of methodological fronts in Quaternary entomology in recent years. Perhaps the most difficult region for sampling organic-rich deposits for fossil beetle analysis is the permafrost zone. Frozen sediments in arctic and subarctic regions can be virtually as hard as rock, and therefore very difficult to sample in bulk. Until recently, most Quaternary beetle studies from permafrost regions have employed the technique of scraping away the soft, surficial layers of sediments that thaw during the summer months. This is painstaking work, and it generally yields only small samples—far less than would be considered ideal for paleoentomological study. However, Kuzmina and Sher (2006) employed a much more rigorous sampling method, as discussed more fully in Sher et al. (2005). They manually chopped thin layers (p5 cm thick) of frozen sediments out of large exposures until they had obtained 50–150 kg of organic detritus per sample. To put this into perspective, these samples were as much as three-times the size of samples taken by Elias et al. (1996) from frozen sediments
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Fig. 1. Map of the world, showing the locations of institutions in which Quaternary beetle research is being done. 1, Fargo, North Dakota, USA (Ashworth, Schwert); 2, Quebec City, Quebec, Canada (Bain, Lavoie); 3, Magadan, Eastern Siberia, Russia (Berman and Alfimov); 4, Ural’sk, Kazakhstan, Russia (Bidashko); 5, Copenhagen, Denmark (Bo¨cher); 6, Bournemouth, UK (Paul Buckland); 7, Umea˚, Sweden (Phil Buckland); 8, Pitlochry, Scotland (Coope); 9, Exeter, UK (Dinnin); 10, London, UK (Elias); 11, River Falls, Wisconsin (Garry); 12, Varberg, Sweden (Gustavson); 13, Sanda, Japan (Hayashi); 14, Falun, Sweden (Hellqvist); 15, York, UK (Kenward); 16, Moscow, Russia (Kuzmina, Sher); 17, Vaexjoe, Sweden (Lemdahl); 18, Christchurch, New Zealand (Marra); 19, St John, New Brunswick, Canada (Miller); 20, Padova, Italy (Minelli); 21, Waterloo, Ontario, Canada (Morgan); 22, Mie, Japan (Mori); 23, Waterville, Maine, USA (Nelson); 24, Marseilles, France (Ponel); 25, Clayton, Victoria, Australia (Porch); 26, Oxford, UK (Robinson); 27, Birmingham, UK (Sadler, Smith); 28, Osaka, Japan (Shiyake); 29, Ottawa, Ontario, Canada (Telka); 30, Amsterdam, The Netherlands (Van Geel); 31, Belfast, Northern Ireland (Whitehouse, Reilly); 32, Compiegne, France (Yvinec); 33, Ekaterinburg, Russia (Zinovjev).
in central Alaska. I have personally sampled blocks of frozen sediment from an exposure in northern Alaska, using a chainsaw. This method is relatively dangerous, and dulls the cutting teeth on the chain in short order, so it is not to be recommended. The Russians have been obtaining their samples by brute force, using hammers and chisels. Once their samples have thawed, they have been screened in the field, using a variation of the bucket-sieve method described in Elias (1994). The Russian method involves the use of a larger piece of sieve screen, fixed into a wooden frame that is built on-site. This allows easier transportation to and from the field, and the resulting sieve box has a larger surface area for screening (approximately 1000 cm2) than that of a bucket sieve, which holds only a conventional sieve-sized screen (approximately 315 cm2). 3. New geographic regions being studied As mentioned above, the study of Quaternary beetle assemblages has expanded geographically in recent years. The researchers who have brought this line of investigation into new countries have faced many of the same problems
as their European and North American predecessors faced in previous decades: lack of trained beetle systematists, lack of detailed information on the modern ranges and habitats of beetles found in Quaternary fossil assemblages, and difficulty in finding grant funds for fossil beetle research. However, good progress is being made in a number of new countries, as follows. 3.1. Australia Work is just getting started in Australia, as doctoral candidate Nick Porch has been investigating fossil assemblages from several sites. As noted in Porch and Elias (2000), one limitation of Quaternary beetle research in Australia is the lack of suitable sites. This is due to a combination of factors: an arid landmass that was even arid during full-glacial periods, the limited extent of Quaternary glaciation, and a lack of exposures at many potential sites. Sites containing Quaternary beetle assemblages (excluding stick-nest rat middens) are currently known only from south-eastern Australia and the Atherton Tableland, but are undoubtedly present in south-western
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Australia and the rest of eastern Australia. The age of currently known faunal assemblages ranges from middle Pleistocene to Holocene. Because the current state of knowledge of Australian beetle species’ distribution and habitat requirements is somewhat incomplete, Porch is relying on a bioclimatic prediction system called BIOCLIM (Busby, 1991) that allows the characterisation of bioclimatic parameters for the fossil taxa, based upon what is known of their modern distribution. 3.2. New Zealand Maureen Marra completed her Ph.D. degree at the University of Wellington in 2002, and has since published a series of papers on Quaternary beetle assemblages in New Zealand (Marra, 2003a, 2003b; Marra and Leschen, 2004; Marra et al., 2004, 2006). Her work has included investigations of a number of sites from South Island and Banks Island. The faunal assemblages have ranged in age from Marine Isotope Stage 6 to the Holocene. As in Australia, the work in New Zealand has been somewhat handicapped by the lack of taxonomic and biological knowledge of the modern fauna. Researchers in New Zealand have developed a Maximum Likelihood Estimation (MLE) method (Marra et al., 2004), in order to compensate for these limitations in modern data. This method merits further discussion. In the MLE method, a database of the modern collecting localities for a given species is converted into GIS Coverage (points) in geographic coordinate space. From this, a climate range distribution for each species is developed from climate surfaces, using GIS. The climate surfaces that have been used are the mean February temperature (warmest month) and mean minimum July temperature (coldest month). The climate surface is represented by 100 m2 cells, and is estimated from fitted spline surfaces. For each grid (i.e., climate surface), the climate variable in each cell corresponding to each collection data point is extracted and entered into a database file (Marra et al., 2004). From this the climate tolerance distribution of each species is defined by a sine function, used to fit maximum likelihood estimates (MLE) of best high and best low values for the distribution of each species in climate space (Marra et al., 2004). Paleotemperature estimates are then based on the overlaps of the climate envelopes of the species found in a fossil assemblage. The lower temperature limits are defined by the species with the highest minimum, and the upper limits are defined by species with the lowest maximum. 3.3. Previously unstudied regions of Russia Evgenij Zinovjev has been expanding Russian paleoentomological research into the Ural Mountains and Western Siberia in recent years (Zinovjev, 2006). His work includes analysis of faunas ranging in age from middle Pleistocene
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to Holocene. As might be expected, the interpretation of fossil beetle assemblages from this enormous, poorly populated region has been hindered by a lack of knowledge concerning the modern ranges and ecological requirements of the insect fauna. This has prevented Zinovjev from attempting such paleotemperature reconstruction methods as the Mutual Climatic Range (MCR) method, which relies upon more extensive knowledge of modern species’ ranges in order for species climate envelopes to be developed. Lacking sufficient modern distribution data for the more traditional paleoclimatic reconstruction methods, Zinovjev has developed an alternative method of paleoenvironmental reconstruction, based on the presence and absence of particular species associations, grouped by ecological types. These types include arctic, subarctic, boreal forest, hardwood forest, sub-boreal azonal and ‘mixed’ (nonanalogue) faunas. He has also taken into consideration the taxonomic structure of fossil assemblages (including family, subfamily and generic composition), as well as the proportion of the various ecological groups. These reconstructions are also closely tied to interpretations based on paleobotanical (plant macrofossil) data. Kuzmina and Sher (2006), Sher et al. (2005) have recently completed a lengthy investigation of Late Pleistocene and Holocene insect assemblages from the Lena Delta region of northeastern Siberia. They have developed a new method of faunal analyses, tailored for Beringian faunas. It is based on the relative proportions of various ecological groups, including xerophilic insects (uncommon or absent in tundra zone), tundra insects, dwarf shrub zone insects, tall shrub zone insects, riparian insects, aquatic insects, and forest zone insects. This approach, based on ecological grouping, is similar in many ways to Zinovjev’s methods, discussed above. Matthews (1983) developed a similar, but much simpler method of ecological classification of Eastern Beringian beetle assemblages. Kuzmina and Sher (2006) have followed a modified version of MCR paleotemperature analysis that has been put forward by Alfimov et al. (2003). The Russians working in north-eastern Siberia have felt the need to modify the original MCR method (Atkinson et al., 1986) because of the lack of diversity of predatory and scavenging beetle species in regional fossil assemblages. The original MCR method uses only these groups of beetles to derive paleotemperature estimates, but the method was developed for use in Western Europe, where Quaternary beetle faunas tend to be relatively rich in predatory and scavenging species. The original method excluded plant-feeding beetle species. The rationale for this exclusion was that the range of phytophagous beetles necessarily reflects the distribution of their host plants, and thus if the response of the host plant to climatic change is relatively slow (i.e., if there is time lag between climate change and plant species response), the phytophagous beetle record will likewise lag behind the climatic change. The history of vegetation change in Europe during multiple glacial–interglacial cycles demonstrates the need
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for caution in the interpretation of the fossil record of phytophagous beetles. However, Alfimov et al. (2003) argue that such is not the case in north-eastern Siberia, for several reasons. The phytophagous species that they are now including in their MCR analyses are not tied to trees, shrubs, or other plant groups that have had a history of large-scale migrations in response to Quaternary climate change. Rather, they are species that feed on mosses or herbs, such as the pill beetles (Byrrhidae) in the genus Morychus and several species of weevils (Curculionidae) in the genus Stephanocleonus. These beetles are ubiquitous in both glacial and interglacial faunal assemblages from north-eastern Siberia. It appears that their host plants (mosses, sedges, and steppe grasses) were likewise present across this region, throughout the Middle and Late Pleistocene. Alfimov and Berman (2002) described a detailed bioclimatic study of modern Stephanocleonus in north-eastern Siberia, as they occur on small patches of relict steppe. Alfimov et al. (2003) have subsequently made use of these data to estimate paleotemperature parameters for Pleistocene fossil assemblages containing these weevils. These parameters include not only mean July temperature, but also the annual sum of daily temperatures above 0 1C (SDD) at the soil surface—a critical factor in insect growth and development in arctic regions. These methods are adding precision to their paleoclimate reconstructions, based on modern ecological observations. 3.4. Links between paleoentomology and archaeology The study of fossil beetle assemblages associated with archaeological sites began in Britain in the late 1960s (Osborne, 1969). There are two principal aims in this line of research. Archaeological sites that predate about 7000 yr BP in northwest Europe usually show little human disturbance of the landscape. This is because huntergatherer societies generally kept moving about the landscape. These early peoples did not greatly disturb the natural environment, because of their lack of settlement in permanent villages, combined with their lack of agriculture and animal husbandry (Elias, 1994). The study of insect faunal assemblages associated with these early human sites is therefore essentially the same as a conventional palaeontological study whose aim is environmental reconstruction of the natural environment. This special issue contains two articles dealing with archaeological studies. The article by Coope (2006) describes insect faunas from some of the earliest known human occupation sites in Britain. Two of the sites are in the English Midlands and the other three of them are in East Anglia. Their stratigraphical contexts can be shown to pre-date the Anglian Glaciation (MIS 12). All these localities contain Palaeolithic artifacts. The assemblages include species that are exotic to Britain today. The presence of these ‘exotics’ allows stratigraphical correlations to be made with other sites in central England. This is particularly important for
the early Palaeolithic period, when stone tool technology apparently remained static for many thousands of years. The faunas also provide detailed information on local environments and regional climates for the English Palaeolithic. The other paper with archaeological associations concerns the rise and fall of primeval forest beetle faunas in Great Britain and Ireland, beginning with initial postglacial colonization, and ending with the widespread clearance of old-growth forests (Whitehouse, 2006). Up to 40 species of forest-associated beetles were extirpated from Britain and 15 species in Ireland, during the latter half of the Holocene. Whitehouse examines the reasons behind these extirpations. The principal causes include forest clearance and other human activities, isolation of populations, lack of temporal continuity of habitats, edaphic and competition factors affecting distribution of host trees (particularly pine), lack of forest fires and a decline in open forest systems. Climate change apparently also played a role, but the extent of this factor is difficult to tease apart from human-induced changes of the landscape. The first human impacts on British forest insects apparently began when people started intensive gathering of dead wood from the forest floor. A rich, diverse beetle fauna is associated with dead and rotting wood in forests. This part of the forest beetle fauna was the first to disappear from the fossil record of most regions, as their habitat was eliminated by human wood foraging. This first wave of extirpations was followed by additional waves, linked with land clearance for agriculture and animal husbandry. A few species of the primeval forest fauna were able to persist until the 19th Century, but nearly all of them have been extirpated from the British Isles, and most of them are in danger of extinction throughout the anthropogenic landscapes of Europe. 4. New techniques being used The fossil beetle papers presented in this special issue of Quaternary Science Reviews highlight several research methods that have recently been developed, or are newly applied to fossil beetle studies. These include new laboratory techniques, such as the extraction and identification of ancient DNA from beetle remains and stable isotope analysis of fossil beetle chitin; they also include new statistical techniques that are being applied to conventional (faunal list) data, in order to estimate past environmental parameters. 4.1. Ancient DNA As reported in Reiss (2006), the study of ancient DNA from insect fossils got off to an poor start in the 1990s, when it was discovered that DNA thought to have come from insects preserved in amber was actually derived from modern contaminants. Subsequent study of ancient DNA from Quaternary beetle remains has focused on specimens
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preserved either in permanently frozen sediments, or in extremely arid conditions, such as packrat (Neotoma) middens from the American Southwest. Both of these extreme environments tend to preserve the integrity of DNA strands over long periods of time. It is generally accepted that the post-deposition survival of DNA is limited to the last 100,000 years, except in very cold conditions. Molecular genetic studies of fossil assemblages have the potential to test the widely held assumption (based on external morphology) that most, if not all beetle species have remained intact for hundreds of thousands (and in some cases, millions) of years (Coope, 1978; Elias, 1994). The basis of ancient DNA research is the polymerase chain reaction (PCR) that facilitates the amplification of a single copy of DNA to greater than one billion copies in 30 cycles. As discussed by Reiss (2006), some of the greatest challenges in ancient DNA research are based on the fact that PCR is such a powerful tool. The tiniest amount of contamination from modern insect DNA can lead to spurious results. Accordingly, the major breakthroughs in the field of ancient insect DNA research have come in the areas of sample purification and contamination avoidance procedures. Work is currently underway to standardize a set of protocols for this work. Reiss (2006) is confident that ‘With appropriate attention to details such as selection of specimen type and species, significant advances will be made in the next decade of insect DNA research.’ 4.2. Hydrogen and oxygen isotopes from Chitin Gro¨cke et al. (2006) report on the most recent analyses of stable isotopes (hydrogen and oxygen) from fossil beetle exoskeletons. Stable isotope geochemical analyses have been performed on Quaternary fossil specimens for more than 20 years, and the initial application of oxygen isotope analyses of beetle chitin was begun in the 1980s (Schimmelmann and DeNiro, 1986; Miller et al., 1988). The most recent advances in this line of research have been made possible because of improved availability of D/H data from precipitation, and by advances in mass-spectrometry that have allowed very small samples to be analysed. Since the sampling method for isotope geochemistry is destructive, researchers were justifiably reluctant to sacrifice dozens of fossil specimens for single analyses. The latest mass-spectrometry techniques are capable of obtaining reliable isotopic data from single exoskeletal sclerites (a head capsule, pronotum, or elytron, for example). The technique is not without its problems, however. The application of stable isotope analyses to derive temperatures is only really effective in the high latitudes (Dansgaard, 1964; Alley and Cuffey, 2001), where correlation between MAT and dD is at its best. The relationship between stable hydrogen isotopes of precipitation and MAT is weak in the lower latitudes. We also need to gain a better understanding of the sources of hydrogen used by beetles to form their exoskeletons. For example, hydrogen in chitin may come
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from ingested food or water, and there is the possibility of isotopic fractionation during digestion and metabolism. The phrase, ‘you are what you eat,’ is quite pertinent to isotopic analysis of beetle chitin. Food sources and the dD of environmental waters change throughout the year. We therefore need a greater understanding of the life history and diet of beetle species chosen for isotopic analysis. In the study by Gro¨cke et al. (2006), ground beetles (Carabidae) were chosen for analysis. The rationale for this was twofold. First, predators are the main group used in MCR paleotemperature reconstructions, so it seems most useful to compare dD results from the same group of beetles that also provide MCR results. Second, the authors argue that predatory beetles are generalist feeders, taking a wide variety of invertebrates as their prey. Their ingested food should therefore represent an averaged dD value for the locality, which should better-reflect meteoric water dD values. In contrast to this, Motz and Morgan (2001) employed a strategy of analysing bark beetles (Scolytidae), which inhabit and feed on trees. Plant-feeding beetles acquire a dD value already fractionated by plants. While such a strategy may solve one problem, it is limited by the lack of bark beetles in most glacial-stage Pleistocene fossil assemblages. Although such ecological and biochemical questions require additional research, the results of these recent studies show the great potential of beetle chitin isotope geochemistry in the reconstruction of past precipitation and temperature. Advances in stable-isotope mass-spectrometry are now providing us with rapid, high-precision analyses of organic stable-isotope ratios. 4.3. New variations on MCR In addition to the MLE method of paleoclimate reconstruction described by Marra et al. (2004, 2006), Bray et al. (2006) have undertaken a series of statistical tests of the original MCR method (as described by Atkinson et al., 1986). The original method yielded ‘raw’ paleotemperature estimates based on MCR, and then attempted to correct for systematic errors in the ‘raw’ estimates through linear regression equations. Bray et al. (2006) describe a problem with this method, however. The problem with the application of linear regression equations to produce corrected MCR estimates is that the method assumes, with little justification, that the beetle population distribution in climate space is normally distributed or at least uni-modal. This can lead to palaeotemperature estimates that are not optimal and also to false precision. By employing ubiquity analysis of species climate envelopes (SCRs), Bray et al. (2006) were able to show that many species populations have bi-modal or even tri-modal distributions in climate space. This invalidates the use of linear regression to calibrate MCR estimates. The application of ubiquity analysis to beetle assemblage data is an extremely labour-intensive procedure. The preliminary work presented by Bray et al. (2006) suggests
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that the method has some utility, but it is too soon to tell whether it is the best way forward. However, their research has validated the strength and utility of the original MCR method. Until additional work in this field is completed, we will have to settle for publishing ‘raw’ MCR estimates. I hasten to point out, however, that many of these estimates are quite tightly constrained, especially estimates of TMAX. For instance, 54 raw MCR estimates for Eastern Beringian Pleistocene beetle faunas (Elias, 2001) had an average TMAX range of just 1.73 1C. The work by Bray et al. (2006) was based on modern European distributions for species found mainly in British Pleistocene assemblages. Because of the time constraints placed on this work (which formed the basis of an M.Sc. thesis), it lacked data from the Asian component of the distribution of many cold-adapted species found in these fossil assemblages. However, as pointed out by Kuzmina and Sher (2006) and by Zinovjev (2006), we generally lack detailed distributional data for many beetle species that live today in the remote regions of northern and eastern Asia. A great deal of collecting data for modern beetle species in these regions has been published only in Russian. A large quantity of species’ distributional data remain to be published, but is available from pinned specimen labels in several Siberian museum collections. These data must be collected and added to the SCRs of beetle species found in Eurasian Pleistocene fossil assemblages, before we can proceed much further with Eurasian MCR studies.
characterization of past climates for terrestrial regions away from the polar ice caps. No one would argue against the utility of deep-sea sediment records that provide seasurface temperature records. Likewise, the value of stable isotope paleothermometry from polar ice cores is unquestioned. However, human beings are always going to be interested in the history of terrestrial environments. It is this aspect of climate history that has shaped our species and our ancestors in the Pleistocene. Coope’s (2006) reconstruction of Middle- to Late Pleistocene environments at British archaeological sites is a forceful reminder of this point. As a Quaternary entomologist, it is exciting for me to see the discipline expand into previously unstudied regions, such as Australia, New Zealand, Japan, and northern Asia. Our branch of science has focussed almost exclusively on Europe and North America since its inception. Along with the new study regions, new schools of thought are also forming in the discipline. Some of these new ideas challenge the research paradigms established by European and North American researchers. While this can admittedly be uncomfortable to those of us in the ‘Old School,’ it is a necessary step forward for the discipline as a whole. Any science that rests on its laurels will soon become moribund. I am happy to report that Quaternary entomology is growing and developing in the 21st Century. Who knows what new analytical tools will be invented in the coming decades?
5. Future directions
References
There are exciting new research directions taking shape in Quaternary entomology. Some of these are extracting new kinds of data from the fossil insect specimens themselves, such as ancient DNA and stable isotopes. The ancient DNA studies hold the promise of proving new insights on the stability of beetle genotypes. Until now, we have inferred long-term genetic stability of beetles from the longevity of ecological compatibility of faunal assemblages (Coope, 1978) and from the morphological constancy of their exoskeletons (Elias, 1994). Now we can begin to address these issues from a genetic perspective. This approach has already enjoyed considerable success with Pleistocene fossil vertebrates (e.g., Shapiro et al., 2004). The study of stable isotopes of H and O from fossil beetle chitin holds the promise of providing an independent proxy for the reconstruction of temperature and precipitation. This is the first new paleoclimate reconstruction tool for Quaternary paleocoleopterists since the development of the MCR method in the 1980s. The isotopic analyses represent a more radical departure from tradition than did MCR, because the latter was just a mathematical extension of the original faunal assemblage analysis methods, developed in the 1950s and 1960s by Coope and others. Within the next few years, it should be possible to derive two independent sets of paleotemperature estimates from one fossil assemblage. This is particularly important for the
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ARTICLE IN PRESS S.A. Elias / Quaternary Science Reviews 25 (2006) 1731–1737 Elias, S.A., 1994. Quaternary Insects and Their Environments. Smithsonian Institution Press, Washington D.C., 284 pp. Elias, S.A., 2001. Mutual Climatic Range reconstructions of seasonal temperatures based on late Pleistocene fossil beetle assemblages in Eastern Beringia. Quaternary Science Reviews 20, 77–91. Elias, S.A., Short, S.K., Waythomas, C.F., 1996. Late Quaternary environments, Denali National Park and Preserve, Alaska. Arctic 49, 292–305. Gro¨cke, D.R., Schimmelmann, A., Elias, S., Miller, R., 2006. Stable hydrogen isotope ratios in beetle chitin: preliminary European data and re-interpretation of North American data. Quaternary Science Reviews, this issue, doi:10.1016/j.quascirev.2006.01.021. Kuzmina, S., Sher, A., 2006. Some features of the Holocene insect faunas of north-eastern Siberia. Quaternary Science Reviews, this issue, doi:10.1016/j.quascirev.2006.01.013. Marra, M.J., 2003a. Last interglacial beetle fauna from New Zealand. Quaternary Research 59, 122–131. Marra, M.J., 2003b. Description and interpretation of a fossil beetle assemblage from marine isotope stage 6 from Banks Island, New Zealand. New Zealand Journal of Geology and Geophysics 46, 523–528. Marra, M.J., Leschen, R.B.L., 2004. Late Quaternary paleoecology from fossil beetle communities in the Awatere Valley, South Island, New Zealand. Journal of Biogeography 31, 571–586. Marra, M.J., Shulmeister, J., Smith, E., 2006. Reconstructing temperature during the Last Glacial Maximum from Lyndon Stream, South Island, New Zealand using beetle fossils and maximum likelihood envelopes. Quaternary Science Reviews, this issue, doi:10.1016/j.quascirev. 2006.01.016. Marra, M.J., Smith, E.G.C., Shulmeister, J., Leschen, R., 2004. Late Quaternary climate change in the Atawere Valley, South Island, New Zealand using a sine model with a maximum likelihood envelope on fossil beetle data. Quaternary Science Reviews 23, 1637–1650. Matthews Jr., J.V., 1983. A method for comparison of northern fossil insect assemblages. Ge´ographie physique et Quaternaire 37, 297–306.
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Miller, R.F., Fritz, P., Morgan, A.V., 1988. Climatic implications of D/H ratios in beetle chitin. Palaeogeography, Palaeoclimatology, Palaeoecology 66, 277–288. Motz, J.E., Morgan, A.V., 2001. Holocene paleoclimate and paleoecology determined from fossil Coleoptera at Brampton, Ontario, Canada. Canadian Journal of Earth Sciences 38, 1451–1462. Osborne, P.J., 1969. An insect fauna of Late Bronze age date from Wilsford, Wiltshire. Journal of Animal Ecology 38, 555–566. Porch, N., Elias, S.A., 2000. Quaternary beetles: a review and issues for Australian studies. Australian Journal of Entomology 39, 1–9. Reiss, R., 2006. Ancient DNA from ice age insects: proceed with caution. Quaternary Science Reviews, this issue, doi:10.1016/j.quascirev. 2006.01.009. Schimmelmann, A., DeNiro, M.J., 1986. Stable isotopic studies on chitin. III. The D/H and 18O/16O ratios in arthropod chitin. Geochimica et Cosmochimica Acta 50, 1485–1496. Shapiro, B., Drummond, A.J., Rambaut, A., Wilson, M.C., Matheus, P.E., Sher, A.V., Pybus, O.G., Gilbert, M.T., Barnes, I., Binladen, J., Willerslev, E., Hansen, A.J., Baryshnikov, G.F., Burns, J.A., Davydov, S., Driver, J.C., Froese, D.G., Harington, C.R., Keddie, G., Kosintsev, P., Kunz, M.L., Martin, L.D., Stephenson, R.O., Storer, J., Tedford, R., Zimov, S., Cooper, A., 2004. Rise and fall of the Beringian Steppe Bison. Science 306, 1561–1565. Sher, A.V., Kuzmina, S.A., Kuznetsova, T.V., Sulerzhitsky, L.D., 2005. New insights into the Weichselian environment and climate of the Eastern-Siberian Arctic, derived from fossil insects, plants, and mammals. Quaternary Science Reviews 24, 533–569. Whitehouse, N.J., 2006. The Holocene British and Irish ancient forest fossil beetle fauna: implications for forest history, biodiversity and faunal colonisation. Quaternary Science Reviews, this issue, doi:10.1016/j.quascirev.2006.01.010. Zinovjev, E.V., 2006. Problems of ecological interpretation of Quaternary insect faunas from the central part of northern Eurasia. Quaternary Science Reviews, this issue, doi:10.1016/j.quascirev.2006.01.017.
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Quaternary beetle research: the state of the art Scott A. Elias Geography Department, Royal Holloway, University of London, Egham, Surrey TW20 0EX, UK Received 6 October 2005; accepted 11 May 2006
Abstract Quaternary beetle research has progressed in a variety of ways during the last decade. New kinds of data are being extracted from the fossil specimens themselves, such as ancient DNA and stable isotopes. The ancient DNA studies hold the promise of proving new insights on the stability of beetle genotypes. The study of stable isotopes of H and O from fossil beetle chitin holds the promise of providing an independent proxy for the reconstruction of temperature and precipitation. The discipline is also expanding into previously unstudied regions, such as Australia, New Zealand, and northern Asia. Along with the new study regions, new schools of thought are also forming in the discipline, challenging old research paradigms. This is a necessary step forward for the discipline, as it grows and develops in the 21st Century. r 2006 Elsevier Ltd. All rights reserved.
1. Introduction When ‘Quaternary Insects and Their Environments’ was published in 1994, most of the research in this field was being done either in Western Europe or in North America. I noted in that book that ‘Many of these researchers have been trained by Russell Coope at the University of Birmingham, or by his former students.’ While most of the same researchers are still active, a number of new paleoentomologists have begun publishing in this field, studying the faunas of new regions. As shown in Fig. 1, the geographic spread of research in Quaternary beetle assemblages now extends to Japan, Australia, and New Zealand. New regions of northern and central Siberia are now being investigated, as are regions in Kazakhstan. As might be expected, the people investigating Quaternary beetle assemblages in these various regions have employed new and different methods of faunal extraction, identification, and interpretation. Because of political and linguistic barriers, some Japanese and Russian researchers were only vaguely aware of the Western European and North American literature in this field when they started out. Some of their indigenous methods are quite distinct from those of Coope and his students, as will Tel.: +44 1784 443647; fax: +44 1784 472836.
E-mail address: [email protected]. 0277-3791/$ - see front matter r 2006 Elsevier Ltd. All rights reserved. doi:10.1016/j.quascirev.2006.05.002
be discussed, below. As this line of research has expanded into new regions, it has also contracted in others. Sadly, research in South America has waned since the publications by Ashworth and others in the 1980s and early 1990s. 2. General advances since 1994 Progress has been achieved along a number of methodological fronts in Quaternary entomology in recent years. Perhaps the most difficult region for sampling organic-rich deposits for fossil beetle analysis is the permafrost zone. Frozen sediments in arctic and subarctic regions can be virtually as hard as rock, and therefore very difficult to sample in bulk. Until recently, most Quaternary beetle studies from permafrost regions have employed the technique of scraping away the soft, surficial layers of sediments that thaw during the summer months. This is painstaking work, and it generally yields only small samples—far less than would be considered ideal for paleoentomological study. However, Kuzmina and Sher (2006) employed a much more rigorous sampling method, as discussed more fully in Sher et al. (2005). They manually chopped thin layers (p5 cm thick) of frozen sediments out of large exposures until they had obtained 50–150 kg of organic detritus per sample. To put this into perspective, these samples were as much as three-times the size of samples taken by Elias et al. (1996) from frozen sediments
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Fig. 1. Map of the world, showing the locations of institutions in which Quaternary beetle research is being done. 1, Fargo, North Dakota, USA (Ashworth, Schwert); 2, Quebec City, Quebec, Canada (Bain, Lavoie); 3, Magadan, Eastern Siberia, Russia (Berman and Alfimov); 4, Ural’sk, Kazakhstan, Russia (Bidashko); 5, Copenhagen, Denmark (Bo¨cher); 6, Bournemouth, UK (Paul Buckland); 7, Umea˚, Sweden (Phil Buckland); 8, Pitlochry, Scotland (Coope); 9, Exeter, UK (Dinnin); 10, London, UK (Elias); 11, River Falls, Wisconsin (Garry); 12, Varberg, Sweden (Gustavson); 13, Sanda, Japan (Hayashi); 14, Falun, Sweden (Hellqvist); 15, York, UK (Kenward); 16, Moscow, Russia (Kuzmina, Sher); 17, Vaexjoe, Sweden (Lemdahl); 18, Christchurch, New Zealand (Marra); 19, St John, New Brunswick, Canada (Miller); 20, Padova, Italy (Minelli); 21, Waterloo, Ontario, Canada (Morgan); 22, Mie, Japan (Mori); 23, Waterville, Maine, USA (Nelson); 24, Marseilles, France (Ponel); 25, Clayton, Victoria, Australia (Porch); 26, Oxford, UK (Robinson); 27, Birmingham, UK (Sadler, Smith); 28, Osaka, Japan (Shiyake); 29, Ottawa, Ontario, Canada (Telka); 30, Amsterdam, The Netherlands (Van Geel); 31, Belfast, Northern Ireland (Whitehouse, Reilly); 32, Compiegne, France (Yvinec); 33, Ekaterinburg, Russia (Zinovjev).
in central Alaska. I have personally sampled blocks of frozen sediment from an exposure in northern Alaska, using a chainsaw. This method is relatively dangerous, and dulls the cutting teeth on the chain in short order, so it is not to be recommended. The Russians have been obtaining their samples by brute force, using hammers and chisels. Once their samples have thawed, they have been screened in the field, using a variation of the bucket-sieve method described in Elias (1994). The Russian method involves the use of a larger piece of sieve screen, fixed into a wooden frame that is built on-site. This allows easier transportation to and from the field, and the resulting sieve box has a larger surface area for screening (approximately 1000 cm2) than that of a bucket sieve, which holds only a conventional sieve-sized screen (approximately 315 cm2). 3. New geographic regions being studied As mentioned above, the study of Quaternary beetle assemblages has expanded geographically in recent years. The researchers who have brought this line of investigation into new countries have faced many of the same problems
as their European and North American predecessors faced in previous decades: lack of trained beetle systematists, lack of detailed information on the modern ranges and habitats of beetles found in Quaternary fossil assemblages, and difficulty in finding grant funds for fossil beetle research. However, good progress is being made in a number of new countries, as follows. 3.1. Australia Work is just getting started in Australia, as doctoral candidate Nick Porch has been investigating fossil assemblages from several sites. As noted in Porch and Elias (2000), one limitation of Quaternary beetle research in Australia is the lack of suitable sites. This is due to a combination of factors: an arid landmass that was even arid during full-glacial periods, the limited extent of Quaternary glaciation, and a lack of exposures at many potential sites. Sites containing Quaternary beetle assemblages (excluding stick-nest rat middens) are currently known only from south-eastern Australia and the Atherton Tableland, but are undoubtedly present in south-western
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Australia and the rest of eastern Australia. The age of currently known faunal assemblages ranges from middle Pleistocene to Holocene. Because the current state of knowledge of Australian beetle species’ distribution and habitat requirements is somewhat incomplete, Porch is relying on a bioclimatic prediction system called BIOCLIM (Busby, 1991) that allows the characterisation of bioclimatic parameters for the fossil taxa, based upon what is known of their modern distribution. 3.2. New Zealand Maureen Marra completed her Ph.D. degree at the University of Wellington in 2002, and has since published a series of papers on Quaternary beetle assemblages in New Zealand (Marra, 2003a, 2003b; Marra and Leschen, 2004; Marra et al., 2004, 2006). Her work has included investigations of a number of sites from South Island and Banks Island. The faunal assemblages have ranged in age from Marine Isotope Stage 6 to the Holocene. As in Australia, the work in New Zealand has been somewhat handicapped by the lack of taxonomic and biological knowledge of the modern fauna. Researchers in New Zealand have developed a Maximum Likelihood Estimation (MLE) method (Marra et al., 2004), in order to compensate for these limitations in modern data. This method merits further discussion. In the MLE method, a database of the modern collecting localities for a given species is converted into GIS Coverage (points) in geographic coordinate space. From this, a climate range distribution for each species is developed from climate surfaces, using GIS. The climate surfaces that have been used are the mean February temperature (warmest month) and mean minimum July temperature (coldest month). The climate surface is represented by 100 m2 cells, and is estimated from fitted spline surfaces. For each grid (i.e., climate surface), the climate variable in each cell corresponding to each collection data point is extracted and entered into a database file (Marra et al., 2004). From this the climate tolerance distribution of each species is defined by a sine function, used to fit maximum likelihood estimates (MLE) of best high and best low values for the distribution of each species in climate space (Marra et al., 2004). Paleotemperature estimates are then based on the overlaps of the climate envelopes of the species found in a fossil assemblage. The lower temperature limits are defined by the species with the highest minimum, and the upper limits are defined by species with the lowest maximum. 3.3. Previously unstudied regions of Russia Evgenij Zinovjev has been expanding Russian paleoentomological research into the Ural Mountains and Western Siberia in recent years (Zinovjev, 2006). His work includes analysis of faunas ranging in age from middle Pleistocene
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to Holocene. As might be expected, the interpretation of fossil beetle assemblages from this enormous, poorly populated region has been hindered by a lack of knowledge concerning the modern ranges and ecological requirements of the insect fauna. This has prevented Zinovjev from attempting such paleotemperature reconstruction methods as the Mutual Climatic Range (MCR) method, which relies upon more extensive knowledge of modern species’ ranges in order for species climate envelopes to be developed. Lacking sufficient modern distribution data for the more traditional paleoclimatic reconstruction methods, Zinovjev has developed an alternative method of paleoenvironmental reconstruction, based on the presence and absence of particular species associations, grouped by ecological types. These types include arctic, subarctic, boreal forest, hardwood forest, sub-boreal azonal and ‘mixed’ (nonanalogue) faunas. He has also taken into consideration the taxonomic structure of fossil assemblages (including family, subfamily and generic composition), as well as the proportion of the various ecological groups. These reconstructions are also closely tied to interpretations based on paleobotanical (plant macrofossil) data. Kuzmina and Sher (2006), Sher et al. (2005) have recently completed a lengthy investigation of Late Pleistocene and Holocene insect assemblages from the Lena Delta region of northeastern Siberia. They have developed a new method of faunal analyses, tailored for Beringian faunas. It is based on the relative proportions of various ecological groups, including xerophilic insects (uncommon or absent in tundra zone), tundra insects, dwarf shrub zone insects, tall shrub zone insects, riparian insects, aquatic insects, and forest zone insects. This approach, based on ecological grouping, is similar in many ways to Zinovjev’s methods, discussed above. Matthews (1983) developed a similar, but much simpler method of ecological classification of Eastern Beringian beetle assemblages. Kuzmina and Sher (2006) have followed a modified version of MCR paleotemperature analysis that has been put forward by Alfimov et al. (2003). The Russians working in north-eastern Siberia have felt the need to modify the original MCR method (Atkinson et al., 1986) because of the lack of diversity of predatory and scavenging beetle species in regional fossil assemblages. The original MCR method uses only these groups of beetles to derive paleotemperature estimates, but the method was developed for use in Western Europe, where Quaternary beetle faunas tend to be relatively rich in predatory and scavenging species. The original method excluded plant-feeding beetle species. The rationale for this exclusion was that the range of phytophagous beetles necessarily reflects the distribution of their host plants, and thus if the response of the host plant to climatic change is relatively slow (i.e., if there is time lag between climate change and plant species response), the phytophagous beetle record will likewise lag behind the climatic change. The history of vegetation change in Europe during multiple glacial–interglacial cycles demonstrates the need
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for caution in the interpretation of the fossil record of phytophagous beetles. However, Alfimov et al. (2003) argue that such is not the case in north-eastern Siberia, for several reasons. The phytophagous species that they are now including in their MCR analyses are not tied to trees, shrubs, or other plant groups that have had a history of large-scale migrations in response to Quaternary climate change. Rather, they are species that feed on mosses or herbs, such as the pill beetles (Byrrhidae) in the genus Morychus and several species of weevils (Curculionidae) in the genus Stephanocleonus. These beetles are ubiquitous in both glacial and interglacial faunal assemblages from north-eastern Siberia. It appears that their host plants (mosses, sedges, and steppe grasses) were likewise present across this region, throughout the Middle and Late Pleistocene. Alfimov and Berman (2002) described a detailed bioclimatic study of modern Stephanocleonus in north-eastern Siberia, as they occur on small patches of relict steppe. Alfimov et al. (2003) have subsequently made use of these data to estimate paleotemperature parameters for Pleistocene fossil assemblages containing these weevils. These parameters include not only mean July temperature, but also the annual sum of daily temperatures above 0 1C (SDD) at the soil surface—a critical factor in insect growth and development in arctic regions. These methods are adding precision to their paleoclimate reconstructions, based on modern ecological observations. 3.4. Links between paleoentomology and archaeology The study of fossil beetle assemblages associated with archaeological sites began in Britain in the late 1960s (Osborne, 1969). There are two principal aims in this line of research. Archaeological sites that predate about 7000 yr BP in northwest Europe usually show little human disturbance of the landscape. This is because huntergatherer societies generally kept moving about the landscape. These early peoples did not greatly disturb the natural environment, because of their lack of settlement in permanent villages, combined with their lack of agriculture and animal husbandry (Elias, 1994). The study of insect faunal assemblages associated with these early human sites is therefore essentially the same as a conventional palaeontological study whose aim is environmental reconstruction of the natural environment. This special issue contains two articles dealing with archaeological studies. The article by Coope (2006) describes insect faunas from some of the earliest known human occupation sites in Britain. Two of the sites are in the English Midlands and the other three of them are in East Anglia. Their stratigraphical contexts can be shown to pre-date the Anglian Glaciation (MIS 12). All these localities contain Palaeolithic artifacts. The assemblages include species that are exotic to Britain today. The presence of these ‘exotics’ allows stratigraphical correlations to be made with other sites in central England. This is particularly important for
the early Palaeolithic period, when stone tool technology apparently remained static for many thousands of years. The faunas also provide detailed information on local environments and regional climates for the English Palaeolithic. The other paper with archaeological associations concerns the rise and fall of primeval forest beetle faunas in Great Britain and Ireland, beginning with initial postglacial colonization, and ending with the widespread clearance of old-growth forests (Whitehouse, 2006). Up to 40 species of forest-associated beetles were extirpated from Britain and 15 species in Ireland, during the latter half of the Holocene. Whitehouse examines the reasons behind these extirpations. The principal causes include forest clearance and other human activities, isolation of populations, lack of temporal continuity of habitats, edaphic and competition factors affecting distribution of host trees (particularly pine), lack of forest fires and a decline in open forest systems. Climate change apparently also played a role, but the extent of this factor is difficult to tease apart from human-induced changes of the landscape. The first human impacts on British forest insects apparently began when people started intensive gathering of dead wood from the forest floor. A rich, diverse beetle fauna is associated with dead and rotting wood in forests. This part of the forest beetle fauna was the first to disappear from the fossil record of most regions, as their habitat was eliminated by human wood foraging. This first wave of extirpations was followed by additional waves, linked with land clearance for agriculture and animal husbandry. A few species of the primeval forest fauna were able to persist until the 19th Century, but nearly all of them have been extirpated from the British Isles, and most of them are in danger of extinction throughout the anthropogenic landscapes of Europe. 4. New techniques being used The fossil beetle papers presented in this special issue of Quaternary Science Reviews highlight several research methods that have recently been developed, or are newly applied to fossil beetle studies. These include new laboratory techniques, such as the extraction and identification of ancient DNA from beetle remains and stable isotope analysis of fossil beetle chitin; they also include new statistical techniques that are being applied to conventional (faunal list) data, in order to estimate past environmental parameters. 4.1. Ancient DNA As reported in Reiss (2006), the study of ancient DNA from insect fossils got off to an poor start in the 1990s, when it was discovered that DNA thought to have come from insects preserved in amber was actually derived from modern contaminants. Subsequent study of ancient DNA from Quaternary beetle remains has focused on specimens
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preserved either in permanently frozen sediments, or in extremely arid conditions, such as packrat (Neotoma) middens from the American Southwest. Both of these extreme environments tend to preserve the integrity of DNA strands over long periods of time. It is generally accepted that the post-deposition survival of DNA is limited to the last 100,000 years, except in very cold conditions. Molecular genetic studies of fossil assemblages have the potential to test the widely held assumption (based on external morphology) that most, if not all beetle species have remained intact for hundreds of thousands (and in some cases, millions) of years (Coope, 1978; Elias, 1994). The basis of ancient DNA research is the polymerase chain reaction (PCR) that facilitates the amplification of a single copy of DNA to greater than one billion copies in 30 cycles. As discussed by Reiss (2006), some of the greatest challenges in ancient DNA research are based on the fact that PCR is such a powerful tool. The tiniest amount of contamination from modern insect DNA can lead to spurious results. Accordingly, the major breakthroughs in the field of ancient insect DNA research have come in the areas of sample purification and contamination avoidance procedures. Work is currently underway to standardize a set of protocols for this work. Reiss (2006) is confident that ‘With appropriate attention to details such as selection of specimen type and species, significant advances will be made in the next decade of insect DNA research.’ 4.2. Hydrogen and oxygen isotopes from Chitin Gro¨cke et al. (2006) report on the most recent analyses of stable isotopes (hydrogen and oxygen) from fossil beetle exoskeletons. Stable isotope geochemical analyses have been performed on Quaternary fossil specimens for more than 20 years, and the initial application of oxygen isotope analyses of beetle chitin was begun in the 1980s (Schimmelmann and DeNiro, 1986; Miller et al., 1988). The most recent advances in this line of research have been made possible because of improved availability of D/H data from precipitation, and by advances in mass-spectrometry that have allowed very small samples to be analysed. Since the sampling method for isotope geochemistry is destructive, researchers were justifiably reluctant to sacrifice dozens of fossil specimens for single analyses. The latest mass-spectrometry techniques are capable of obtaining reliable isotopic data from single exoskeletal sclerites (a head capsule, pronotum, or elytron, for example). The technique is not without its problems, however. The application of stable isotope analyses to derive temperatures is only really effective in the high latitudes (Dansgaard, 1964; Alley and Cuffey, 2001), where correlation between MAT and dD is at its best. The relationship between stable hydrogen isotopes of precipitation and MAT is weak in the lower latitudes. We also need to gain a better understanding of the sources of hydrogen used by beetles to form their exoskeletons. For example, hydrogen in chitin may come
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from ingested food or water, and there is the possibility of isotopic fractionation during digestion and metabolism. The phrase, ‘you are what you eat,’ is quite pertinent to isotopic analysis of beetle chitin. Food sources and the dD of environmental waters change throughout the year. We therefore need a greater understanding of the life history and diet of beetle species chosen for isotopic analysis. In the study by Gro¨cke et al. (2006), ground beetles (Carabidae) were chosen for analysis. The rationale for this was twofold. First, predators are the main group used in MCR paleotemperature reconstructions, so it seems most useful to compare dD results from the same group of beetles that also provide MCR results. Second, the authors argue that predatory beetles are generalist feeders, taking a wide variety of invertebrates as their prey. Their ingested food should therefore represent an averaged dD value for the locality, which should better-reflect meteoric water dD values. In contrast to this, Motz and Morgan (2001) employed a strategy of analysing bark beetles (Scolytidae), which inhabit and feed on trees. Plant-feeding beetles acquire a dD value already fractionated by plants. While such a strategy may solve one problem, it is limited by the lack of bark beetles in most glacial-stage Pleistocene fossil assemblages. Although such ecological and biochemical questions require additional research, the results of these recent studies show the great potential of beetle chitin isotope geochemistry in the reconstruction of past precipitation and temperature. Advances in stable-isotope mass-spectrometry are now providing us with rapid, high-precision analyses of organic stable-isotope ratios. 4.3. New variations on MCR In addition to the MLE method of paleoclimate reconstruction described by Marra et al. (2004, 2006), Bray et al. (2006) have undertaken a series of statistical tests of the original MCR method (as described by Atkinson et al., 1986). The original method yielded ‘raw’ paleotemperature estimates based on MCR, and then attempted to correct for systematic errors in the ‘raw’ estimates through linear regression equations. Bray et al. (2006) describe a problem with this method, however. The problem with the application of linear regression equations to produce corrected MCR estimates is that the method assumes, with little justification, that the beetle population distribution in climate space is normally distributed or at least uni-modal. This can lead to palaeotemperature estimates that are not optimal and also to false precision. By employing ubiquity analysis of species climate envelopes (SCRs), Bray et al. (2006) were able to show that many species populations have bi-modal or even tri-modal distributions in climate space. This invalidates the use of linear regression to calibrate MCR estimates. The application of ubiquity analysis to beetle assemblage data is an extremely labour-intensive procedure. The preliminary work presented by Bray et al. (2006) suggests
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that the method has some utility, but it is too soon to tell whether it is the best way forward. However, their research has validated the strength and utility of the original MCR method. Until additional work in this field is completed, we will have to settle for publishing ‘raw’ MCR estimates. I hasten to point out, however, that many of these estimates are quite tightly constrained, especially estimates of TMAX. For instance, 54 raw MCR estimates for Eastern Beringian Pleistocene beetle faunas (Elias, 2001) had an average TMAX range of just 1.73 1C. The work by Bray et al. (2006) was based on modern European distributions for species found mainly in British Pleistocene assemblages. Because of the time constraints placed on this work (which formed the basis of an M.Sc. thesis), it lacked data from the Asian component of the distribution of many cold-adapted species found in these fossil assemblages. However, as pointed out by Kuzmina and Sher (2006) and by Zinovjev (2006), we generally lack detailed distributional data for many beetle species that live today in the remote regions of northern and eastern Asia. A great deal of collecting data for modern beetle species in these regions has been published only in Russian. A large quantity of species’ distributional data remain to be published, but is available from pinned specimen labels in several Siberian museum collections. These data must be collected and added to the SCRs of beetle species found in Eurasian Pleistocene fossil assemblages, before we can proceed much further with Eurasian MCR studies.
characterization of past climates for terrestrial regions away from the polar ice caps. No one would argue against the utility of deep-sea sediment records that provide seasurface temperature records. Likewise, the value of stable isotope paleothermometry from polar ice cores is unquestioned. However, human beings are always going to be interested in the history of terrestrial environments. It is this aspect of climate history that has shaped our species and our ancestors in the Pleistocene. Coope’s (2006) reconstruction of Middle- to Late Pleistocene environments at British archaeological sites is a forceful reminder of this point. As a Quaternary entomologist, it is exciting for me to see the discipline expand into previously unstudied regions, such as Australia, New Zealand, Japan, and northern Asia. Our branch of science has focussed almost exclusively on Europe and North America since its inception. Along with the new study regions, new schools of thought are also forming in the discipline. Some of these new ideas challenge the research paradigms established by European and North American researchers. While this can admittedly be uncomfortable to those of us in the ‘Old School,’ it is a necessary step forward for the discipline as a whole. Any science that rests on its laurels will soon become moribund. I am happy to report that Quaternary entomology is growing and developing in the 21st Century. Who knows what new analytical tools will be invented in the coming decades?
5. Future directions
References
There are exciting new research directions taking shape in Quaternary entomology. Some of these are extracting new kinds of data from the fossil insect specimens themselves, such as ancient DNA and stable isotopes. The ancient DNA studies hold the promise of proving new insights on the stability of beetle genotypes. Until now, we have inferred long-term genetic stability of beetles from the longevity of ecological compatibility of faunal assemblages (Coope, 1978) and from the morphological constancy of their exoskeletons (Elias, 1994). Now we can begin to address these issues from a genetic perspective. This approach has already enjoyed considerable success with Pleistocene fossil vertebrates (e.g., Shapiro et al., 2004). The study of stable isotopes of H and O from fossil beetle chitin holds the promise of providing an independent proxy for the reconstruction of temperature and precipitation. This is the first new paleoclimate reconstruction tool for Quaternary paleocoleopterists since the development of the MCR method in the 1980s. The isotopic analyses represent a more radical departure from tradition than did MCR, because the latter was just a mathematical extension of the original faunal assemblage analysis methods, developed in the 1950s and 1960s by Coope and others. Within the next few years, it should be possible to derive two independent sets of paleotemperature estimates from one fossil assemblage. This is particularly important for the
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