Insular biogeography of mammals in Canadian parks: a re‐analysis

Abstract

Summary Aim Glenn & Nudds (1989) compared mammal species richness in Canadian parks to estimated species‐area relationships prior to European settlement to test if parks presently contain their historical compliment of species. However, the data they used to estimate the presettlement species‐area relationships were not commensurate with the scale of the parks and were not independent. This uncertainty reduces the utility of Glenn and Nudds analysis to detect which, if any, parks are experiencing mammal extirpations and ultimately to direct conservation efforts to enhance mammal conservation in Canada. We improved Glenn and Nudds methods and re‐assesed the conservation status of mammals in Canadian parks. Location Canada. Methods We constructed species‐area curves for disturbance tolerant and intolerant species in five mammal regions of Canada by sampling historical range maps using plots of 10– 10,000 km2. We compared these estimates of expected species richness to current species richness in thirty‐six parks and contrast our results with those of Glenn and Nudds. Results All ten re‐estimated species‐area regressions had higher intercepts than those reported by Glenn and Nudds; four had lower slopes. Of seventy‐two cases analysed, we found twenty in which parks had fewer species than expected and four in which parks had more species than expected, compared to fourteen and thirty‐three, respectively, reported by Glenn and Nudds. Changes in both the regression parameters and increases in the prediction intervals accounted for the disparity between these results. Park residuals were not significantly different from zero in eight of ten analyses. Residuals for parks in the Alleghenian‐Illinoian mammal province were negative and decreased with increasing park size. Main conclusions Improvement of Glenn and Nudds methods had an effect on both the parameter estimates and precison of the presettlement species‐area curves. As a result, mammal conservation in some Canadian parks is worse than Glenn and Nudds reported. Six additional parks contained fewer disturbance intolerant species than predicted. However, Glenn and Nudds finding of systematic differences between expected and observed species richness in parks in the densely populated region of southern Ontario, southern Quebec and the maritime provinces was not an artefact of their methods. In this region, seven of ten parks appear to have lost disturbance‐sensitive species of mammals. The pattern of species loss in this region was consistent with the idea that these parks have become isolated from mammal dispersal by surrounding habitat change and have experienced local species extirpations.