Genetic diversity and demographic history of the Siberian lime (Tilia sibirica).

Tilia sibirica Bayer (Siberian lime) is endemic to the low mountain systems north of the Altai Mountains of southern Siberia, approximately 1,000 kms to the east of the natural range limit of its closest congeneric, the small-leaved lime ( Tilia cordata ). Some consider the taxon to be a subspecies of T. cordata . This putative pre-Last Glacial Maximum (LGM) relict may have had a stronghold in a refugium of the Altai Mountains and survived various waves of fluctuating climatic changes that occurred in the region. With continued climatic changes expected, these hardy but isolated populations can be important sources for population expansion. To date, we do not know the genetic status or history of this forest tree. This study uses standard population genetic and Approximate Bayesian Computation (ABC) analyses of microsatellite data to determine the genetic diversity and differentiation, clonal occurrence and date of divergence of the two lime taxa. The results show that T. sibirica and T. cordata are distinct biological units with significant genetic differentiation. The ABC analysis suggests a (Middle) Pleistocene divergence. We have revealed low within-population genetic diversity as well as high levels of clonality in T. sibirica. The focus now should be on restoring and conserving these small and isolated relict populations. [ABSTRACT FROM AUTHOR]