Population Structure of Pedunculate Oak (Quercus robur L.) in Lithuania Based on Analysis of Chloroplast DNA Haplotypes and Adaptive Traits

Abstract

The latest was probably conditioned by adaptive processes that modified the features of populations. The Jurava, Bijutiskis, Siesikai, Kulupenai, Gustonys and Seirijai populations consist of genotypes of three cpDNA haplotypes which indicate that these stands were established artificially and with mixture of seeds from different populations. While populations with predominance of haplotype 2 or 7 or combination of haplotypes 5 and 6 can be considered as autochthonous. The coefficient of genetic variation of adaptive traits was from 10.8 to 32.3% and varied in different populations from 0 to 51.8 % thus reflecting differing adaptation possibilities of populations. However, a certain amount of additive genetic variation of adaptive traits cannot be attributed to particular cpDNA haplotype. The identified comparatively large chloroplast DNA haplotype diversity and genetic variation of adaptive traits suggests that species have a potential for genetic adaptation to changes of climate and environment and indicate good possibilities for gene conservation and tree breeding in Lithuania when using the Multiple Population Breeding System. Present climate change and increased amplitude of its variation, increasing damages of pedunculate oak stands and plantations caused by spring frosts, fungi and insect outbreaks, threatens the survival of populations and rises the concern for gene conservation and tree breeding. This study aimed at defining the role of postglaciai migration routes and origin of populations on population structure and genetic variation in relation to possibilities for genetic adaptation for uncertain future climate, gene conservation and tree breeding. The PCR-RFLP analysis of chloroplast DNA of samples from 7 trees from each of 29 Lithuanian pedunculate oak populations revealed three distinct groups of populations. East Lithuanian populations Semeliskes (Trakai), Dukstos and Paezeriai (Vilnius) and Ignalina belong to the cpDNA haplotype 2 from C lineage that migrated to Lithuania from South Italian glacial refuge zone. Haplotype 7 from A lineage of the northern Balkans origin dominates in Central-South Lithuania, while haplotypes 5 and 6 from A lineage originating from the South-East Balkans are typical for West-North Lithuanian populations. This haplotype distribution in Lithuania well corresponds to the oak provenance regions that have been defined based on oak stands productivity and morphologic traits and on eco-climatic parameters of geographic regions. It indicates that separate migration routes of pedunculate oak from different ice age refuge populations across Lithuania contributed to formation of large scale patchy geographical structure, provenance regions in Lithuania and probably reflect features of the former ice age populations that survived in refuge zones in southern Europe. However, no similarities were found with population structure that was defined by analysis of phenology, most important adaptive trait.