Climate-induced range shifts of mammals and reptiles: demography at range edges

点击翻译按钮获取中文摘要

Climate change is forecast to have serious and long-lasting impacts on Canada's wildlife species. Some species are likely to extend their ranges northward, while others may be driven extinct in Canada. Predicting how species will respond is of critical importance for Canada, so that appropriate management can be planned. At present, about half of Canada's mammal species and all of the reptiles have small geographic ranges at their northern range edges within Canada. The majority of these species are found in southern Canada, where human-caused habitat fragmentation threatens their populations. Many of these species are listed as Threatened or Endangered under the Species at Risk Act or are listed provincially. The dominant theory about range edges suggests that these populations occur at lower densities and with worse survival and reproduction than core populations. These ideas have been challenged recently as many northern range edge populations are rapidly expanding northwards as climate change makes new areas suitable. Recent theory suggests that range edge populations may in fact favour the evolution of high dispersal and reproductive rates. Further, range edge populations may be more tolerant of habitat fragmentation because conditions on the range edge are over-all worse than in the range core, thus favoring individuals able to tolerate poor habitats. The research I propose addresses how Canada's mammals and reptiles at their northern range limits will respond to climate change. Field-based projects on three species will test whether range edge and core populations are affected by habitat fragmentation in the same way. Analyses of densities, survival rates, and reproductive rates for mammals and reptiles across their geographic ranges will test how similar range core and range edge populations are in their demography. Finally, a statistical model for all Canadian mammals and reptiles will test whether species traits (e.g. body mass, diet, dispersal ability) affect their range edge dynamics. Collectively, these projects will contribute both to ecological theory about why ranges stop and to the management of Canadian species at their northern range edges.