Effects of Predation, Competition, and Isolation on the Rate of Shell Selection in the Hermit Crab Pagurus Longicarpus

S 81 increased population size of both species and expansion of the boreal forest, a likely result of global climate change, have caused areas of geographic overlap to occur. The Trumpeter and Tundra Swans are known to be reproductively compatible, as a viable hybrid population exists in Virginia at the Airlie Center’s Swan Research Program (SRP). Further, accounts from local wildlife managers indicate the presence of fertile hybrids in overlapping breeding areas in Alaska. This research seeks to confirm the presence of viable wild hybrids and to elucidate the genetic structure and relatedness of these interbreeding populations by comparison of phylogenetically relevant genetic loci of wild individuals to known hybrids from the SRP. We will also incorporate “historic” samples collected in 1920 (and prior) to confirm that this interbreeding is a recent phenomenon and likely due to habitat disturbance from climate change. EFFECTS OF PREDATION, COMPETITION, AND ISOLATION ON THE RATE OF SHELL SELECTION IN THE HERMIT CRAB PAGURUS LONGICARPUS. Amber L. King & Deirdre Gonsalves-Jackson, Biology Department, Virginia Wesleyan College. Hermit crabs are most notably known for their use of gastropod shells to protect their soft bodies, which lack calcification on their abdominal exoskeleton. Because of the necessity for a gastropod shell, hermit crabs will often fight amongst each other for shells due to the scarcity of available shells because without a shell to provide adequate protection, they risk exposure. Pagurus longicarpus was used in this study to determine the effect of various factors on the rate of shell switching, specifically the effect of isolation, conspecifics, and predation. It was proposed that more hermit crabs would switch shells and the rate of shell switching would increase when isolated, rather than when in the presence of conspecifics or a predator. Three different treatments were set up and based on the results, the two hypotheses were supported because more hermit crabs switched shells and at a faster rate in the isolation treatment, rather than in the other two treatments, suggesting that predation may have posed as significant a threat in my study because the hermit crabs failed to switch shells.