Genetic diversity at chloroplast SSR LOCI in Siberian fir (Abies sibirica Ledeb.): Comparison with allozyme data

Semerikova S.A., Semerikov V.L.

Institute of Plant and Animal Ecology, RAS, semerikov@ipae.uran.ru

Genetic variation in 31 populations of Abies sibirica was investigated with cpSSR markers. Young in 26 of those populations the allozyme analysis was conducted (Semerikova, Semerikov, 2006; Semerikova, 2006). Two pairs of primers (Pt71936 and Pt30204) out of ten examined (Vendramin et al., 1996) gave consistent amplification and were polymorphic. Forty-three haplotypes comprising six alleles in locus Pt71936 and eleven alleles in locus Pt30204 were found in 1269 trees of A. sibirica. Diversity estimates significantly fluctuated among investigated populations. Smallest haplotype number and lowest genetic diversity was observed in the populations of the Southern Urals and in some populations of West Siberia. The highest diversity was found in South Siberia, along Yenissey river and in the Baikal area. The highest number of the unique and rare haplotypes was found also in some populations of South Siberia, Baikal Lake area, and the smallest number was found in the Southern and Middle Urals.

Inter-population proportion of the genetic variation in A. sibirica, computed with account of the genetic differences between haplotypes (R_ST) and without taking into account these differences (G_ST) were 7.89% and 4.16%, respectively (R_ST>G_ST, P=0.01), suggesting that related haplotypes had a tendency to co-occur in the same populations. Pairwise G_ST significantly correlated with geographic distances between populations of A. sibirica and with Nei’s genetic distances based on allozyme data. However, correlations of the pairwise R_ST with the same parameters were absent. Inter-population genetic diversity estimated with cpSSRs was lower then the allozyme-based one (Semerikova, Semerikov, 2006). In general the analysis of the cpSSR variation in A. sibirica supported the conclusions based on the allozyme data that indicated subdivision of the populations into several geographic groups probably originated due to post glacial migration from separate refugia.

In spite of the vast geographic range, A. sibirica displays relatively small genetic variation, characterized by polymodal distributions of the microsatellite lengths due to the presence in A. sibirica of a few common haplotypes, genetically quite separated from each other, together with numerous rare haplotypes, closely related with some of the former. These common haplotypes could be the survivals of the bottleneck in the past of A. sibirica, strongly reducing haplotype diversity. The more rare and phylogenetically close to the former haplotypes could have originated from them lately.

Differences in haplotype diversity rate among populations and regions as well as reduced diversity in some populations could be the result of relatively recent local population shrinking. High haplotype diversity in South Siberia and the Baikal Lake area confirm the hypothesis that glacial refugia of evergreen conifer vegetation were located in this area. Populations of the Altai Mts are different from northward located populations by allozymes and by cpSSRs, thus rejecting significant impact of the Altai on the colonization of the West and North Siberia.

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