Submission Type
Oral Presentation
Abstract
Island rodent populations frequently exhibit island gigantism, presenting with larger body sizes in comparison to mainland counterparts. Proposed mechanisms to explain gigantism include benign island habitats and lack of mainland predators and competitors. However, island populations tend to be denser than mainland populations, increasing conspecific competition. With extrinsic sources of pressure largely missing from island habitats, conspecific competition may become a selecting force for larger body sizes in island populations. Here we examine presence of gigantism in North American deermouse (Peromyscus maniculatus) populations throughout the Gulf Islands of British Columbia, Canada and assess if population density is an underlying mechanism. Deermouse populations were live trapped on nine of the Gulf Islands as well as on the lower mainland of British Columbia to assess gigantism. We found that deermouse populations on islands have larger body mass than populations inhabiting the mainland. However, no significant relationship was found between population density and body mass. Due to the large variation in ecological composition of islands selected for study, follow-up analyses were conducted on other possible mechanisms. Study sites with reports of higher predator species richness were found to have smaller mice in comparison to islands with few to no predator species reported. Gigantism continues to be a complex phenomenon likely driven by several mechanisms. Furthermore, these mechanisms may vary across metapopulations, requiring further study.
Included in
Giant mice on small islands: mechanisms of gigantism in Peromyscus maniculatus Gulf Island populations
Island rodent populations frequently exhibit island gigantism, presenting with larger body sizes in comparison to mainland counterparts. Proposed mechanisms to explain gigantism include benign island habitats and lack of mainland predators and competitors. However, island populations tend to be denser than mainland populations, increasing conspecific competition. With extrinsic sources of pressure largely missing from island habitats, conspecific competition may become a selecting force for larger body sizes in island populations. Here we examine presence of gigantism in North American deermouse (Peromyscus maniculatus) populations throughout the Gulf Islands of British Columbia, Canada and assess if population density is an underlying mechanism. Deermouse populations were live trapped on nine of the Gulf Islands as well as on the lower mainland of British Columbia to assess gigantism. We found that deermouse populations on islands have larger body mass than populations inhabiting the mainland. However, no significant relationship was found between population density and body mass. Due to the large variation in ecological composition of islands selected for study, follow-up analyses were conducted on other possible mechanisms. Study sites with reports of higher predator species richness were found to have smaller mice in comparison to islands with few to no predator species reported. Gigantism continues to be a complex phenomenon likely driven by several mechanisms. Furthermore, these mechanisms may vary across metapopulations, requiring further study.
Comments
Pirmin Nietlisbach
Illinois State University