Butterfly assemblages along a human disturbance gradient in

Abstract: This study relates patterns of butterfly abundance and species richness to position along an urban distur-bance gradient in southeastern Ontario, Canada. Observed assemblages along the gradient (N = 15) included butterflies from the Papilionidae, Pieridae, Lycaenidae, Nymphalidae, and Hesperiidae families. Of the total 26 observed species, 15 were noticeably absent from the disturbed sites. Butterfly assemblages had equal or higher number of individuals and species richness at moderately disturbed sites compared with the least disturbed sites. In relation to distribution patterns along the gradient, 28 % of butterfly species were classified as disturbance adaptable and 58 % as disturbance avoiders. These classifications were correlated with host-plant use and voltinism. Canonical correspondence analysis of local-scale data strongly associated disturbance avoiders with a specific environmental variable (e.g., Everes comyntas (Godart, 1824) with grasslands), whereas disturbance-adaptable species were weakly associated with any variable. One-time disturbances (i.e., mowing) during the survey resulted in pronounced changes in butterfly abundance and species composition at two sites, reducing species richness and total abundance by up to 80%. Species were patchily distrib-uted along the gradient, suggesting that they respond differentially to disturbance in the landscape. Résumé: Notre étude met en relation les répartitions d’abondance et de richesse spécifique chez les papillons, d’une part, et leur position le long d’un gradient de perturbation urbaine dans le sud-est de l’Ontario, Canada, d’autre part. Les regroupements observés le long du gradient (N = 15) comprennent des papillons des familles Papilionidae, Pie