Biogeography and conservation of the pinnipeds (Carnivora: Mammalia)

Higdon, Jeffrey Wayde

Biogeography and conservation of the pinnipeds (Carnivora: Mammalia)

dc.contributor.author	Higdon, Jeffrey Wayde
dc.contributor.examiningcommittee	Walker, David (Environment and Geography) Stern, Gary (Environment and Geography) Davoren, Gail (Biological Sciences) Morris, Douglas (Lakehead University)	en
dc.contributor.supervisor	Ferguson, Steve (Environment and Geography)	en
dc.date.accessioned	2011-01-14T21:53:52Z
dc.date.available	2011-01-14T21:53:52Z
dc.date.issued	2011-01-14T21:53:52Z
dc.degree.discipline	Environment and Geography	en_US
dc.degree.level	Doctor of Philosophy (Ph.D.)	en_US
dc.description.abstract	This thesis examines the biogeography of world pinnipeds, a unique group of marine mammals that have adapted to marine foraging while maintaining terrestrial (land or ice) habitat links. Comparative analyses of species range sizes controlled for phylogenetic relationships using a multi-gene supertree with divergence dates estimated using fossil calibrations. Adaptations to aquatic mating and especially sea ice parturition have influenced range size distribution, and ranges are larger than those of terrestrially mating and/or pupping species. Small range size is endangering for many taxa, and most at risk pinnipeds are terrestrial species with small ranges. Ancestral state reconstructions suggest that pinnipeds had a long association with sea ice, an adaptation that would have allowed early seals to expand into novel habitats and increase their distribution. Range sizes exhibit a strong Rapoport effect (positive relationship between range size and latitude) at the global scale, even after controlling for phylogeny and body size allometry. A latitudinal gradient in species diversity cannot explain the Rapoport effect for global pinniped ranges, as diversity is highest at mid-latitudes in both hemispheres. These regions are characterized by marginal ice zones and variable climates, supporting a mix of pagophilic and temperate species. The climatic variability hypothesis also did not explain the Rapoport effect. Variability is bimodal, and annual sea surface temperature (SST) variability does explain diversity patterns. Range size has a significant negative relationship with annual mean SST, and the largest ranges are found in areas with low mean SST. Temperature responses are possibly related to thermoregulation, sea ice availability, and ecological relationships with other large marine predators. These results agree with other studies and suggest that ocean temperature, and not productivity, drives marine species richness patterns. Future research needs include studies of physiological tolerances, interactions with sharks as predators and competitors, and the role of climate and sea ice in speciation and evolution. A better understanding of distribution and diversity patterns, and the role of the environment in shaping these patterns, will improve conservation efforts, and studies on the role of SST and sea ice are particularly important given current warming trends and declines in ice extent.	en
dc.description.note	February 2011	en
dc.format.extent	1009569 bytes
dc.format.extent	1009569 bytes
dc.format.mimetype	application/pdf
dc.format.mimetype	application/pdf
dc.identifier.citation	Higdon, J.W., O.R.P. Bininda-Emonds, R.M.D. Beck, and S.H. Ferguson. 2007. Phylogeny and divergence of the pinnipeds (Carnivora: Mammalia) assessed using a multigene dataset. BMC Evolutionary Biology 7:216.	en
dc.identifier.uri	http://hdl.handle.net/1993/4346
dc.language.iso	eng	en_US
dc.rights	open access	en_US
dc.subject	seals	en
dc.subject	marine mammals	en
dc.subject	evolution	en
dc.subject	phylogeny	en
dc.subject	distribution	en
dc.subject	sea ice	en
dc.subject	climate	en
dc.subject	species richness	en
dc.title	Biogeography and conservation of the pinnipeds (Carnivora: Mammalia)	en
dc.type	doctoral thesis	en_US