Resources influence dispersal and population structure in an endangered butterfly

. The degree of dispersal between patches in a population partly determines its structure. Mark-release-recapture (MRR) studies of an archipelago population of the endangered apollo butterfly (Parnassius apollo, L 1758) revealed that most (79%) adult individuals remained within the patch where they were marked. . Emigration out of a patch was female-biased and decreased with the amount of (adult) nectar resources on a patch, but increased with greater proximity to nectar on other patches. Local population numbers positively correlated with total numbers of both emigrants and immigrants. Host-plant abundance (larval resource) did not influence dispersal. . The dispersal and population structure of this archipelago population differs pronouncedly from that of a previously studied mainland population where between-patch dispersal is more frequent even when correcting for differences in habitat structure between the populations, and consequently the population structure is more patchy or open. . The most prominent environmental factor affecting emigration is nectar resources. Both local patch conditions in terms of nectar on the patch and nectar availability on surrounding patches are important. . The most important implications for conservation are that resource distribution affects dispersal and hence population-level processes such as structure, and that emigration and immigration should be viewed as separate processes potentially governed by different environmental factors.