Jerry Belant and Julie Van Stappen(1) have been using genetic data to estimate the abundance of black bears on the islands of the Apostle Islands National Lakeshore, and to study the pattern of movement between islands and from the islands to the mainland. In this figure (below) the Bayesian clustering program Structure was used to identify the primary split in the genetic data. This split separates the population on Stockton Island(2) from the populations on Oak Island, Sand Island(3) and the mainland. Stockton individuals with orange bars are presumed to be immigrants to Stockton Island while individuals with red bars elsewhere in the archipelago are presumed to have emigrated from Stockton Island. Rapid genetic drift caused by small population size is thought to have facilitated the remarkable genetic divergence between areas in the face of high migration rates.
(1)National Park Service; see Belant, Van Stappen & Paetkau in press Ursus ??.
(2)Estimated population size based on genetic mark-recapture = 26.
(3)Estimated population size based on genetic mark-recapture = 7.

Movement in Florida Black Bears

Jeremy Dixon(1) and his colleagues have been monitoring two previously isolated black bear populations as black bears start to re-occupy the intervening habitat. We produced genetic data that Jeremy used to assign individuals (circles) to their birth populations (colour), showing that movement into the corridor has been overwhelmingly from the southern, Ocala population. A variety of evidence suggests that the Ocala population has expanded in recent years, pointing to a pattern of density-dependent dispersal.
(1)University of Florida & Florida Fish and Wildlife Conservation Commission