Invasion genetics of the Eurasian spiny waterflea (Bythotrephes longimanus): Evidence for bottlenecks and multiple origins using microsatellites.
Colautti, Robert*,1, MacIsaac, Hugh1, Heath, Daniel1, 1 Great Lakes Institute for Environmental Research (GLIER), Windsor, Ontario, Canada
ABSTRACT- The Eurasian spiny waterflea (Bythotrephes longimanus) is a predacious zooplankter invasive to North America's Great Lakes region. We isolated five microsatellite DNA loci with between 5 and 19 alleles per locus. We sampled three populations where B. longimanus has been historically present (Switzerland, Italy, and Finland) as well as an introduced European population (Netherlands) and three North American populations (Lakes Erie, Superior, Shebandowan). Consistent with a bottleneck during colonization (i.e., founder effect), average heterozygosities of the four European populations ranged from 0.310 to 0.599, and were higher than that of three North American populations (0.151 to 0.220). Pairwise FST estimates among North American (0.002 to 0.063) populations were not significantly different from zero and were much lower than among European populations (0.208 to 0.474). This is consistent with a scenario of high gene flow among North American populations relative to that of European ones. Contrary to an invasion bottleneck, however, Erie and Superior populations contained similar numbers of rare alleles as European populations. Assignment tests identified several migrant genotypes in all introduced populations (Netherlands, Erie, Superior, Shebandowan), but rarely in native ones (Switzerland, Italy and Finland). A large number of genotypes from North America were assigned to our Italian population implicating a second, previously unidentified, invasion source somewhere in the region of northern Italy. Together, our results support an invasion bottleneck for North American populations that has been largely offset by gene flow from multiple native sources combined with gene flow among introduced populations.
Key words: invasion genetics, bythotrephes longimanus, invasive species, genetic diversity
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