OF GROUND-BEETLES AND MEN: INTRODUCED SPECIES AND THE SYNANTHROPIC FAUNA OF WESTERN CANADA

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Abstract
Assemblages of carabid beetles occurring in anthropogenic habitats in western Canada include native and introduced species. In this study, about 70% of the native species encountered in anthropogenic habitats have their main centres of abundance in native grassland. Twenty species known from British Columbia are of recent European origin. These species were probably introduced in ballast carried by commercial sailing vessels or in shipments of nursery stock. The species that have successfully colonized western Canada cannot be distinguished from a random sample of the estimated source fauna with respect to either taxonomic distribution or body size. However, all introduced species are characteristic of disturbed and/or anthropogenic habitats in Great Britain and are strictly synanthropic in British Columbia. Where they occurred, introduced species were usually numerically dominant members of anthropogenic assemblages. Both flight and human-assisted transport must be invoked to explain the patterns of range expansion observed for introduced species. Although the presence of introduced species was correlated with reduced diversity of native species, the carabid fauna of western Canada has been generally enriched because only one native species is strictly synanthropic.