Genotyping-by-Sequencing Analysis Shows That Siberian Lindens Are Nested within <i>Tilia cordata</i> Mill
2022
Sergei V. Shekhovtsov | Irina N. Shekhovtsova | Oleg E. Kosterin
<i>Tilia sibirica</i> and <i>T. nasczokinii</i> are considered to be endemic Siberian linden species. They have very small distributions located hundreds to thousands of kilometers away from other lindens. It is unclear how closely these species are related to the widespread <i>Tilia cordata</i>: according to the current hypotheses, they could be pre-Pleistocene relicts or remnants of the recent continuous range of <i>T. cordata</i> that existed during the Holocene climatic optimum. Earlier studies detected significant differences between <i>T. sibirica</i>, <i>T. nasczokinii</i>, and <i>T. cordata</i> in microsatellite loci, but not in plastid sequences. Here we performed a phylogenetic analysis of several linden species based on GBS data. The obtained GBS sequences were assembled to create phylogenetic trees based on 16,000–294,000 variable sites. We found that <i>T. cordata</i> and the two putative Siberian species formed a monophyletic group. It consisted of three clades: the basal clade containing specimens from the Caucasus, and two sister clades representing populations from the East European Plains+the Urals and Siberia, respectively. Neither of the Siberian species was related to the Far Eastern <i>T. amurensis</i>, as was hypothesized earlier. Our study suggests that the colonization of Europe and Siberia after the Last Glacial Maximum occurred from different glacial refugia.
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