Colonization, extinction, and phylogeographic patterning in a freshwater crustacean.

Phylogeographic analyses have revealed the importance of Pleistocene vicariance events in shaping the distribution of genetic diversity in freshwater fishes. However, few studies have examined the patterning of variation in freshwater organisms with differing dispersal syndromes and life histories. The present investigation addresses this gap, examining the phylogeography of Sida crystallina, a species whose production of diapausing eggs capable of passive dispersal was thought to constrain its regional genetic differentiation. By contrast, the present analysis has revealed deep allozyme and cytochrome oxidase I mitochondrial DNA divergence between populations from North America and Europe. Moreover, North American populations are separated into four allopatric assemblages, whose distribution suggests their derivation from different Pleistocene refugia. These lineages show higher haplotype diversity and deeper sequence divergence than those of any fish from temperate North America. Its distinctive life history traits have evidently sheltered lineages of Sida from extinction, contributing to a remarkably comprehensive and high resolution phylogeographic record.