Impact of past climatic changes on genetic diversity in Arctic and boreal Species
Friday seminar by Vadim B. Fedorov from University of Alaska Fairbanks
Understanding the biological consequences of climate change for high latitude biota is of critical importance for assessment and prediction of future scenarios. A promising approach to improve our knowledge about biotic effects of climate change is to study genetic diversity in modern species and infer their demographic history. The past 1.2 M years was marked by cycles of glacial interglacial changes and this is used as a model system to infer past distributional and demographic changes from genetic diversity in modern populations and correlating demographic events with the past climate change. The strong phylogeographic structure revealing distinct regional phylogenetic groups has been found in the Arctic for several species of rodents that were sampled on circumpolar scale. The extent of sequencing divergence between major intraspecific clades in most cases suggests separation over several full glacial cycles. Another important insight from population genetics studies is that cryptic northern refugia were important sources for colonization of formerly glaciated high latitude regions in Scandinavia and Canada. Besides glacial advances, genetic diversity of cold adapted Arctic species was influenced by warm climatic events during interglacials and the Holocene. Arctic specialist, the collared lemming demonstrates low genetic diversity in northern tundra regions affected by northward forest expansions during the Holocene warm climatic events in the Eurasian Arctic. The low genetic diversity and coalescence times suggest that the collared lemming suffered a reduction in effective population size due to range contraction during warming events. Consistently, drastic reduction in effective population size during postglacial warming event was recently demonstrated by ancient DNA analysis in one population of the collared lemming in northern Eurasia. In contrast to Arctic species, the lack of phylogeographic structure associated with significant reciprocal monophyly and genetic signatures of demographic expansion in boreal forest animal species studied to date across most of northern Eurasia imply contraction of each species to a single refugial area during the late Pleistocene followed by range expansion on a continental scale.
Vadim B. Fedorov
Institute of Arctic Biology, University of Alaska Fairbanks