Long‐Distance Dispersal and Colonization in the Bay Checkerspot Butterfly, Euphydryas Editha Bayensis

Abstract

Dispersal, patch finding, and colonization abilities of the Bay checkerspot butterfly (Euphydryas editha bayensis) were measured in field experiments. Butterflies released in non—habitat were capable of moving several kilometres to reach a distant habitat patch. However, their interhabitat movements appeared to be non—oriented, unless they were within 50 m of a suitable patch. To quantify colonization ability, I transplanted propagules of 100 postdiapause larvae each to 38 vacant habitats. Twenty—four transplants (63%) produced adults in the initial year, and 6(25%) of these initially successful transplants persisted to produce adults one year later. Thus the chances of successful population establishment, given the presence of gravid female on a vacant habitat, appear to be low (i.e., at most a 6.25% chance of persisting 2 yr). The present distribution of the butterfly suggests that hilly intervening terrain inhibits the colonization of distant habitat patches. These results shed additional light upon the dynamics of a metapopulation of the Bay checkerspot butterfly.