| Summary: | This study used molecular markers to examine patterns of genetic variation and post-glacial dispersal in three species of freshwater zooplankton from glaciated North America. A survey of both mitochondrial and allozyme variation in the cladoceran ' Sida crystallina' revealed the presence of four allopatric assemblages derived from separate Wisconsinan refugia. Divergence between phylogroups was deeper than that previously observed for refugial lineages of freshwater fishes subject to the same glaciation events. Examination of mtDNA variation at two genes in the arctic anostracans ' Branchinecta paludosa' and 'Arlemiopsis stefanssoni' revealed a divergent phylogeographic history. 'A. stefanssoni' populations derive from a single glacial refuge, while 'B. paludosa ' occupied several refugia. The distribution of these phylogroups supports the presence of high arctic refugial lineages of both species in the Canadian arctic. Results from this study highlight the importance of life history characteristics including body size, diapause, and generation time in determining the ability of different taxa to persist in glacial refugia during the Pleistocene.
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