General patterns of intraspecific variations in pine (Pinus L.) and spruce (Picea A. Dietr.)

Forest Ecology and Management, 11 (1985) 5--15

5

Elsevier Science Publishers B.V., Amsterdam -- Printed in The Netherlands

G E N E R A L PATTERNS OF I N T R A S P E C I F I C V A R I A T I O N S IN PINE (PINUS L.) AND SPRUCE (PICEA A. DIETR.)

L.F. P R A V D I N

Science Academy of the U.S.S.R.,Laboratory of Forestry, Uspenskoje, 143030, Moscow Region (U.S.S.R.) (Accepted 29 November 1984)

ABSTRACT Pravdin, L.F., 1985. General patterns of intraspecific variations in pine (Pinus L.) and spruce (Pieea A. Dietr.). For. Ecol. Manage., 11: 5--15.

Morphological, anatomical, physiological and ecological characteristics of Scots pine and three species of spruce were investigated over an extensive territory of the Euroasian part of the U.S.S.R., which gives great possibilitiesin their breeding.

INTRODUCTION

Coniferous plants are considered to have emerged during the Cretaceous period, which makes tracing the evolution of this plant group (over such a long period) rather difficult.In order to elicitthe causes of the present-day distribution of the conifers and to show patterns of their intraspecific diversity, or the direction of their macroevolution, one should take into account all the geological events which occured in the North of the Russian mainland during the Holocene. First of all, tectonic movements changed the absolute altitude above ocean level and gave rise to variations of the thermal conditions in latitudes of the temperate climate zone. The main cause of planetary cooling t h r o u g h o u t the earth surface, according to the latest geological data (Markov, 1966), is the elevation of the surface of the Continent during the Pleistocene. At the same time, the ocean floor was submerging. The change in land height amounted to 500 m, which in some places caused a doubling (and even more) of the continental height. It is accepted that a height increase of 100 m decreases the average temperature by 0.6°C, at least where the troposphere thickness is within 10 km of the height interval over the entire relief. Thus, the tectonic m o v e m e n t s contributed significantly (by 3°C on average) to the cooling of the land surface. The more sharply expressed continental climate of North Euroasia compared with North America gave rise to the diversity of their glacial covers. The centres of huge glacial covers were widely distributed over the tern0378-1127/85/$03.30

© 1985 Elsevier Science Publishers B.V.

perate or subarctic zones, but not in the Arctic. The glaciation occurred in the least outliers of Asia also (Nalivkin, 1960) during the middle or even early part of the quarternary period. Later on glaciation spread down a further 2000--3000 m, and as result, river valleys and hills were submerged. The land bridge between Asia and America was broken quite recently, at the end of the Holocene, i.e. 5000--6000 years ago. The submergence of vast territories caused the breakage of plant and animal ranges. This event forms the basis of the present
Pine Spruce

Number of species North America

Euroasia

60 10

35 27

Reference

Critchfield and Little (1966) Bobrov (19 71)

mined from a number of morphological, physiological and cytogenetical characters and properties. The section Casicta Mayr from the Ajanensis Bobr. series of the spruce genus only comprises three species that grow in Euroasia, Picea jezoensis (Sieb. et Zucc.) Cart., P. hondoensis Mayr and P. ajanensis (Lindl. et Gord.) Fisch., and one species in North America, P. sitchensis (Bong.) Carr. The present-day series of Ajanensis may be considered as a link of t w o spruce species growing in Euroasia and North America. When one compares the spruce and pine ranges in these continents, it is not difficult to determine that the ranges of Scots pine (Pinus sylvestris L.) and Norway ( c o m m o n ) spruce (Picea abies (L.) Karst.) are the most extensive ones over Euroasia. VARIATIONS IN SCOTS PINE (PINUS SYLVESTRIS L.) The geographical variations of many characters in Scots pine -- size, morphology and anatomy of needles, cones and seeds, life span, and seasonal variations in needle pigments, chemical composition of seeds, photosynthesis, respiration and growth rate, and k a r y o t y p e , have been investigated by us. The variations in each of the quantitative characters follows a general pattern. Though strong variations in needle size were observed, due to external conditions (including the weather), it is still possible to distinguish regions where long, short, or medium-sized needle pines are prevalent. It is of importance that this character is hereditary and persists even when the Scots pine is introduced to another physio--geographical region. The same applies to cone size, number of seed scales, seed weight, and quantitative characters. B u t along with this it is possible to distinguish regions where variations in these characters follow no such pattern. The life span o f needles is n o t e w o r t h y and believed to be of very high diagnostic significance. In spite of its considerable variation which often depends on weather conditions and fungal diseases, this character is timed for certain geographical regions. In the northern part of the range and in eastern and southern Asia the needles persist for more than 5--6 years, while in the west and central parts of the range they are usually shed after 2--3 years. A distinct b o u n d a r y suggests itself, dividing the range of Scots pine into two vast areas -- a western area with a short needle life span and an eastern one with longer-living needles. It is quite significant that this boundary, though not coinciding fully with western limits of Picea obovata Lbd., Larix sukaczewii Djil., Pinus sibirica (Du Jour), and Abies sibirica L., has in general the same direction. This pattern is n o t accidental, and its causes include both the effect of moist Atlantic climate and c o m m o n migration routes of these tree species from isolated locus, i.e. refugiums (Schmidt-Vogt, 1977). Resin d u c t arrangements in needles are also very important diagnostic

characters (Pilger, 1926; Shaw, 1914). Data obtained convincingly showed that needle anatomy in Scots pine from the southern part of the range in Asia was clearly different from that in other areas of its distribution. This difference is particularly marked in the marginal populations of pine forests of North Kazakhstan. This character and the high number of resin ducts in needles led to the hypothesis of a hybrid nature of Scots pine in Western Europe and North Kazakhstan. Hybridization of Scots pine could have occurred as far back as in the end of the Tertiary, when ranges of Tertiary ancestors of these recent species were adjoining or probably overlapped. Confirmation of this hypothesis is found in works of Larsen (1956), Gaussen {1966), Vidakovi~ (1963), and others. Abnormal anatomy of needles, namely a third vestigal bundle between two vascular bundles, is also worth mentioning (Pravdin, 1969). Variations in fat and nitrogen content in Scots pine seeds (average seed samples from different populations} are so minute that they can be considered almost stable. X-ray photography of seeds, after Gustaffson and Simak (1958-1959), is a good indicator of the geographical variation in seed size and quality. Seasonal changes in pigments of Scots pine needles is known to be a heritable character. One of the causes of needle chlorosis

o

tlBIIIItts

tllllllltl

b

c

d

e

tttllllll8 llttlllllll lllltlltll8

Fig. 1. Idiograms of chromosomes of five subspecies of Scots pine: (a) ssp. lapponica Fries; (b) ssp. sylvestri8 L.; (c) ssp. hamata (Steven) F o m i n ; (d) ssp. sibirica Ledebour; (e) ~ p . kulundensis Sukaczew (Pravdin et al., 1978).

in the autumn and winter is a sharp decrease in chlorophyll content. Respiration in the forms of pines in which needles turn yellow in the winter is much more intensive than in forms of pines in which needles remain green. Needle chlorosis in the winter is to be regarded as an eco-geographic character and an adaptation to environmental conditions that change sharply with the season. Needle chlorosis is strongest during the autumn--winter season in north pines, from Scandinavia, the Kola Peninsula, and northern Siberia. Needles of pines that grow in the Caucasus remain green during the year, not only in natural habitats but also when cultivated far beyond the areas of its natural distribution. The karyotypes of Scots pine from Tuva SSSR, North Kazakhstan, central European parts of the U.S.S.R. and Sweden show essential differences (Abaturova, 1978). Chromosome idiograms are represented in Fig. 1. On the base of variations of the characters studied, five subspecies are distinguished (Pravdin, 1969): (1) Pinus sylvestris L., subsp, sylvestris L.; (2) Pinus sylvestris L., subsp, hamata, or caucasian, P. sylvestris L., subsp. hamata, (Steven) Fomin; Psosnowsky nakai; (3) Pinus sylvestris L., subsp, lapponica Fries; (4) Pinus sylvestris L., subsp, sibirica Ledebour; (5) Pinus sylvestris L., subsp, hulundensis Sukaczew. 10

50

20

3 0 4 0 5 0 ~ ~/0801CX]_12,Qlr.J3160601:~1 7 0 1 8 0

170.

"L~:=~c~,-~-~..~_: _ -- _-;--.-;;---::-:~'_-----W:-.-/ii "--=--.'-.---=_----.------,---\ ~ ',.7~-#-_. ----- / - - ! - \:-, - -;---- ._ ~;~ ~ ' , , . ~-~-... ,. :--_--__.; -__~ _ __~_ _ __,.. .... ,,

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40

h, ° i

.

.

.

.

40

30

70 ~ ' "

80

/

90

i

100

=o=,oo,,o . . . . .

Fig. 2. Ranges of subspecies of Scots pine: (1) ssp. lapponicus Fries; (2) ssp. sylvestris L.; (3) ssp. hamata (Steven) Fornin; (4) ssp. sibirica Ledebour; (5) ssp. kulundensis Sukaczew.

10

The ranges of these five pines are represented in Fig. 2. Trials for effect of seed provenance on p r o d u c t i o n and growth of cultures showed that use of seed of five subspecies outside their natural range was unsuccessful and should be avoided. F o r each subspecies of Scots pine seed for forest plantations must be used within the range of a given climatic ecotype. Within a given climatic e c o t y p e seed use must be conducted with consideration of edaphic and p h y t o c e n o t i c ecotypes. The most effective m e t h o d is the individual selection of trees from populations for growth rate, w o o d quality, resistance to adverse factors, resin yield, and other economically important characters. VARIATIONS IN SPRUCE (PICEA A B I E S AND PICEA OBOVA TA )

Two species of Norway spruce and Siberian spruce o c c u p y the largest areas of Euroasia compared with other spruce species over the mainland. However, there is no consensus of the t a x o n o m i c state of these two species. Some authors (Lindquist, 1948) consider them a variety, others (Sukachev, 1928; Bobrov, 1971) consider them as independent species. The cause of this misunderstanding lies in the history o f these species; in the past their ranges were disconnected, and only after the latest glaciation, i.e. about 4000--5000 years ago, t h e y m e t in the course of migration to form a vast band of a hybrid form in the sympatric zone (Bobrov, 1971). This circumstance formed the basis of the more detailed research of variation in these two species and their natural hybrids. The method accepted was similar to that of Morgenstern and Farrar (1964) and Roche (1969). The most important diagnostic characters distinguishing Norway spruce from Siberian spruce, as considered b y many dendrologists, are given in Table 2. TABLE 2 Diagnostic characters of Norway spruce and Siberian spruce

Characters Ripe cones: length (cm) thickness (cm) Ovuliferous

Seed length (ram) Needle length (mm) Pubescence of annual shoots Season o f seed dispersion

Norway spruce

Siberian spruce

Reference

10--15 3--4 elongated erosodentate sinuate 4--5 10--25

4--8 1--2 broad rounded in margins integerrimus 3.5--4 7--20

Sukachew (1928)

glabrous or thin-haired March--April

thick-haird September

11 The characters listed in Table 2 were taken as initial ones for studying variation in these species. Spruce with features of intermediate character is assumed to be the result of the introgressive hybridization between these two species. The shape of the ovuliferous scales was divided into the following five groups {Fig. 3): (1) Spruce with rounded (integerrimus) margin scales -- Siberian spruce; (2) Seed scale slightly sinuate, in f o r m close to group 1; (3) Seed scales slightly elongated and dentate, in form close to group 4; (4) Seed scales strongly elongated, dentate in m a r g i n s - Norway spruce; (5) Seed scales long, undulate, n o t tightly adjacent, in form acuminate. A five-group scale was adopted for the pubescence of annual shoots: from 0 (hairless) to 4 (hairiness expressed strongly) (Lindquist, 1948). The mean character coefficient was determined for the populations where spruce of different cone shape and shoot pubescence occurred with a different group. When the data based on the above indices were mapped, ranges of Norway spruce, Siberian spruce and their hybrids were clearly distinct. The dispersion analysis showed a high positive correlation among the characters: cone shape and its length, n u m b e r of scales, total temperature

I

0

I

i

2cm

Fig. 3. Photograph of spruce cones a n d scales in the U.S.S.R.: (1) Picea obovata Ledebour, 53°N, 105°E; (2) P. obovata Ldb. X P. abies (L.) Karst., 63°N, 35°E; (3) P. abies (L.) Karst. X P. obovata Ldb., 61°N, 46°E; (4) P. abies (L.) Karst., 54°N, 29°E; (5) P. abies (L.) Karst., f. acuminata Beck, 52°N, 23°E (Pravdin, 1975).

12 TABLE 3 Karyotypes of Norway spruce and Siberian spruce Species

Norway spruce Siberian spruce

Sample origin

N u m b e r and morphology and samples Number B-chromosomes Isobrachial 2n

Heterobrachial

Carpathians

24

none

8

4

Krasnoyarsk (city)

24

1B-3B

9

3

above 10°C, annual precipitation, vegetation season with temperatures above 10°C; the negative correlation among cone shape and pubescence of shoot, north latitude and especially east longitude, absolute temperature minimum, and also a lack of correlation among cone shape and needle length and absolute maximum temperature. The analysis of the data indicates that Norway spruce and Siberian spruce are two well-expressed species, and their intermediate forms are the result of the introgressive hybridization. The nomenclature Picea X fennica (Regel) Kom. is given to this hybrid form (Flora of European part of the U.S.S.R., 1974). The karyotype analysis of Norway spruce (Pravdin et al., 1978), and Siberian spruce (Kruklis, 1971) showed essential differences in karyotypes of these species (Table 3). Norway spruce has no additional B-chromosomes, but in Siberian spruce their number varies from 1B to 3B. The difference in number of isobrachial chromosomes (8 and 9) of heterobrachial (4 and 3) is distinct for Norway and Siberian spruce respectively (Pravdin et al., 1978). The extent of variation in two spruce species and in their hybrids over the Euroasian territory makes it possible to use this information in selective breeding work. Geographical variations in spruce from British Columbia investigated by Taylor (1959), Roche (1969) and others, are of great interest. Their method of investigation was analogous to ours. They proved that white spruce (Picea glauca (Moench) Voss. ssp. glauca) and Engelmann spruce (P. glauca (Moench) Voss ssp. Engelmannii (Parry) Taylor) came into hybridization and formed a wide hybrid zone. Variations of transitive hybrid forms are genetically conditioned. The transition from "pure" white spruce to "pure" Engelmann spruce through hybrid forms is a progressive phenomenon. The hybrid generations show a high variability in timing of the dormancy and growth onset depending on a geographical position of the seeds. The selective factor is the environment, therefore the silvicultural significance of the geographical variations is evident from Roche's work (1971).

13 CONCLUSIONS

Scots pine The wide range of Scots pine and high degree of polymorphism expressed in the species are the main factors which led to the designation of not only series, varieties, forms, races, and subspecies; but even independent species within the taxon P. sylvestris L. The following scheme of the intraspecific subdivisions is based on the "International Rules of Botanical Nomenclature" and ecological principles. The study of variations of the characters described above in Scots pine resulted in the subdivision of the species into five subspecies, or geographical races: (I) Pinus sylvestris L. subsp, sylvestris L.; (II) Pinus sylvestris L. subsp, hamata (Steven) Fomin; (III) Pinus sylvestris L. subsp, lapponica Fries; (IV) Pinus sylvestris L. subsp, sibirica Ledebour; (V) Pinus sylvestris L. subsp, kulundensis Sukaczew. Since the variations of the characters defining a subspecies are subject to geographical variations (adaptation to environmental conditions as the natural selection), "subspecies" here is considered to be the synonym of "geographical race" after many authors or "geographical ecotype" after Turesson. Based on affinity for other important characters in five groups or subspecies which indicate their common ancestry (common needle composition relating them to Dyploxylon subgenus, similar wood texture, range over Euroasia only) it is believed more correct to keep the subspecies designation for these five taxa.

Norway spruce The highly expressed polymorphism and population heterogeneity of Norway spruce is the consequence of history during pre- and post-glacial periods. Analyses of samples (more than 300) collected from natural populations throughout the territory of the U.S.S.R. and paleobotanic data (cone fossils) indicate that populations of two spruce species were isolated territorially: Picea abies (L.) Karst. within the West and P. obovata Ledebour in the East in the preglacial period. The distribution of the spruce populations, over the areas which were realized after retreat of the glaciers, had spread from those refugia where these two species had been saved. The distribution followed three pathways: (1) from Siberia throughout the Urals to Lapland and Fennoscandinavia; (2) from the Schwarzwald and Balkan peninsula, and (3) from the Alps, Appenins, and Franconwald (F.R.G.). Where these population flows met, the conditions for the introgressive (spontaneous) hybridization were created, and as a result a wide zone

14 60

70

10 ~ f -

~0 3Q ,40 50

70

~

130 'J60 . 150.170

180

80

170

70

60

4C

~)0

60

70

80

90

100

110

120

130

140

Fig. 4. Area of Picea obovata Ledebour (A); P. abies (L.) Karst. (C); and their spontaneous hybrids (B) (= P. fennica (Regel) Komarov; Pravdin, 1975).

of hybrid spruce populations was formed over the Russian Plain. The genetic structure of the present-day spruce populations is the consequence of strong variations in hybrid generations and natural selection. A map of the spruce range c o m p o s e d by us at population level is presented in Fig. 4. The present-day isolation of allopatric populations of the spruce and also specificities of the spruce k a r y o t y p e s prove that there are t w o species to deal with: P. abies (L.) Karst. in the West and P.obovata Ledeb. in the East. As for the wide zone at the Russian Plain occupied by sympatric spruce populations; the investigations we carried o u t support the opinion of preservation of the varieties Picea fennica Regel., Puralensis Tepl., P. medioxima Nyl., P. × uwarowi Kaufm., as geographical separation is the basis o f their distinction. The genetical investigations performed and the map c o m p o s e d on that basis reflects Vasilov's point of view that further selective breeding work is needed to raise the productivity of spruce forests.

REFERENCES

Abaturova, G.A., 1978. The k a r y o t y p e s of Scots pine in the European part of the U.S.S.R. In: Scientific basis of coniferous tree selections. Nauka, Academy of Sciences of the U.S.S.R., Moscow, pp. 66--81. Bobrov, E.G., 1971. Generis picea historia et systematica. In: Novitates systematicae plantarum vascularium, t. 7. Nauka, Leningrad, pp. 5--40. Critchfield, W.B. and Little, E., 1966. Geographic distribution of the Pines of the World. U.S. Dept. of Agriculture, Washington, DC, Forest Service, February, 97 pp.

15 Gaussen, H., 1966. Les Gymnosperms Actuelles et Fossiles, 8. Toulouse, Fascicule VI, Chapitre XI, 272 pp. Generalites, genre pinus. Flora Partis Europaeae URSS, Vol. 1, 1974. Nauka, Leningrad, 404 pp. Gustafsson, A., Simak, M., 1958 - - 1959. Effekt of X- and Y-rays on conifer seed. Medd. Statens Skogsforskningsinst., Bd. 48, N. 5. Kruclis, M.V., 1971. Additional chromosomes in gymnosperms (Picea obovata). Dokl. Akad. Nauk S.S.S.R., 196: 1213. Larsen, C.S., 1956. Genetics in Silviculture. Essential Books, London, 224 pp. Lindquist, B., 1948. The main varieties of Picea abies (L.) Karst. in Europe. Acta Horti Berg., 14 (7): 249--342. Markov, K.K., 1966. Noveyshie stranici istorii Semli. Priroda, Moscow, 5: 21--32. Morgenstern, E.K. and Farrar, J.L., 1964. Introgressive hybridization in red spruce and black spruce. Univ. T o r o n t o Fac. For. Tech. Rep., No. 4, 46 pp. Nalivkin, D.V., 1960. Jarkaja stranica geologicheskoy istorii Asii. Priroda, Moscow, 8: 35--42. Pilger, R., 1926. In: A. Engler and K. Prantl (Editors). Die naturlichen Pflanzenfamilien, 13. Leipzig. Pravdin, L.F., 1969. Scots Pine. Variation, intraspecific t a x o n o m y and selection. Copyright 1969, Isreal Program for Scientific Translations, Jerusalem, Ipst Vat. N. 5499. (Translated from Russian, Nauka, Moscow, 1964, 190 pp.) Pravdin, L.F., 1975. I~'cea abies (L.) Karsten and Picea obovata Ledebour in the U.S.S.R. Academy of Sciences of the U.S.S.R., Nauka, Moscow, 176 pp., Tab XXI. Pravdin, L.F., Abaturova, G.A. and Shershukova, O.P., 1976. Karyological analysis of European and Siberian spruce and their hybrids in the U.S.S.R. Silvae Genet., 25 (3,4): 89--95. Pravdin, L.F., Shershukova, O.P. and Abaturova, G.A., 1978. Karyological investigations of the coniferous species o f forest trees. In: Scientific Basis of Coniferous Tree Selections, Academy of Sciences o f the U.S.S.R., Nauka, Moscow, pp. 45m65. Roche, L., 1966. Spruce provenance research in British Columbia. In: Proc. 10th Meet. Comm. For. Tree Breed. Can. Dept. Fish. For., pp. 107--121. Roche, L., 1968. Introgressive hybridization in the spruce species of British Columbia. In: Proc. l l t h Meet. Comm. For. Tree Breed. Can. Dept. Fish. For., pp. 249--269. Roche, L., 1969. A geneaological study of the genus Picea in British Columbia. New P h y t o l . , 6 8 : 504w554. Roche, L., 1971. Variation, selection and breeding of coniferous tree species. Canadian Forestry Service, Quebec, 74 pp. Shaw, G.R., 1914. The genus Pinus. Riverside Press, Cambridge, 96 pp. Schmidt - - Vogt, H., 1977. Die Fichte. Taxonomie, Verbreitung, Morphologie, Okologie. Waldgesellschaften, Hamburg und Berlin, Vol 1 , 6 4 7 pp. Sukachev, V.N., 1928. Lesnie porodi. Cictematika, geographia i phytosociologia ich. Coniferus. Picea. Novaja derevnja, 80 ctr. Taylor, T.M.C., 1959. The t a x o n o m i c relationship between Picea glauca (Moench) Voss and P. engelmannii Parry. Madrono, 15 : 112--115. Vavilov, N.I., 1922. The law of homologous series in variation. J. Genetics. 12 (1): 47--89. Vidakovi~, M., 1963. Interspecific crossing between Serbian spruce (Picea omorica (Pancic) Purkyne) and Sitka spruce (Picea sitchensis (Bong.) CarT.). Sumarstvo, 10-12: 337--342.