GENETIC-CHARACTERIZATION OF AN ARCTIC ZOOPLANKTER - INSIGHTS INTO GEOGRAPHIC POLYPLOIDY

Species of Bosmina from the temperate regions of North America and Eur ope are diploid and reproduce by cyclical parthenogenesis. By contrast , this study provides evidence that the dominant bosminid taxon in Hig h Arctic lakes reproduces by obligate parthenogenesis and is a polyplo id derived from interspecific hybridization. Sinobosmina liederi, a sp ecies common in temperate North America, is likely to have been one pa rent of these hybrids, but the other parent is unknown. As neither par ent was detected in the Arctic, it seems unlikely that the hybrid clon es that now occupy arctic lakes were synthesized locally. Most habitat s contained only one or two clones, despite a total of 38 clones in th e region, suggesting that priority effects have been important in rest ricting diversity within single lakes. The high regional diversity of arctic bosminids could reflect either repeated hybridization between t he parent taxa or the genetic instability of newly formed polyploid li neages. These processes would produce hybrid polyploids that are consi derably more diverse than their sexual parent taxa, and this differenc e in genetic diversity may confer an advantage to the polyploid biotyp e. As many zooplankton taxa from the arctic possess genetic characteri stics similar to those of bosminids, these processes may provide a gen eral explanation for the widespread occurrence of polyploids in the Ar ctic.