Winter filtering, immigrant selection and species composition of insular mammals of Lake Huron

Patterns in species composition of small mammals on islands of northwestern Lake Huron, USA were studied to test the hypothesis that insular community structure was strongly influenced by immigrant selection, l e, selection for the more vagile species Of 17 insectivores and rodents in the mainland pool nine were detected on at least one of the 25 islands studied These species comprised a biased subset of the mainland pool, biased in favor of species with relatively good winter immigration abilities The five true hibernators were absent from all islands studied and the two winter-inactive species occurred on just two islands Frequency of insular occurrence increased with level of winter activity (hibernator vs winter-inactive vs winter-active) and with body size (p < 0.02)
The winter filtering effect remains one of the best documented forms of immigrant selection In general however, insular community structure is influenced by the combined effects of selective extinction as well as selective immigration Common insular species are those which combine relatively high immigration abilities with low resource requirements