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Abstract:

Daphnia has quickly emerged into model organism in ecology and evolution research. As a result it has been subjected to extensive studies in eco-toxicology, ecological genomics and population genetics studies. However, most of the population genetics studies of Daphnia have concentrated in temperate population and a few from arctic Canada. Given to its sensitivity to climate change, the expansion of such study into the polar region is of paramount importance. What is more, the study of population structure and diversity of organisms from the polar region can provide a unique opportunity to make inferences about postglacial colonization in areas that have recently been de-glaciated due to climate change and contribute to our understanding of colonization dynamics and founder events. Here, we assessed the spatial population genetic structure of Daphnia pulex spp. complex from a gradient of lakes and ponds in Greenland, which are recently created due to melting of the Greenland Ice Sheet. 61 population were sampled from 21 lakes and 40 ponds that vary in area, size and depth and genotyped at 9 microsatellite loci. Based on 9 microsatellite loci, we scored 1-9 MLGs/population which vary in their distribution, clonal diversity and mean clonal richness in each habitat studied. Clonal diversity ranges 1.22 to 3.65 and 1.22 to 3.72 for Lakes and ponds respectively. 20-90% expected heterozygosity was observed for both lakes and ponds. Furthermore, these ponds/lakes harbor two/more of the polyploidy members of Daphnia pulex spp. (i.e. Daphnia pulicaria, and Daphnia middendorffiana). However, Daphnia pulicaria seems to dominate [i.e. having high frequency of occurrence] compared to Daphnia middendorffiana. In general, our finding support hypothesis that polyploidy is dominant in marginalised and higher latitude. But this needs further confirmation by increasing the number individuals genotyped in a population and genetic marker used.