Behavioral and life-history variability in migration

Abstract As habitats vary, selection for migration varies in intensity and pattern across space and time, with the result that migratory life-history syndromes and the routes and connectivity between regions also vary. The variation may occur among and within species, and there may be major life history differences between migrants, non-migrants, and partial migrants. Examples include more vigorous activity among cane toads on an invasion front and muscle histolysis following flight to promote reproduction in insects. Variation in routes followed may occur within populations at different seasons or in the overall pattern between populations, as is the case when leapfrogging occurs. Migratory variation in distance traveled can influence reproductive traits such as clutch size in birds. Partial migration has been the subject of theoretical analysis including evolutionarily stable strategy (ESS) models. Depending on conditions, degrees of trade-off occur among migration strategies. The action of natural selection on migration has resulted in both long-term evolution and evolution in contemporary time.