| Abstrakt: |
Urbanization is increasing worldwide with important consequences on biodiversity. We evaluated how plant species richness, functional diversity and beta diversity differ in four anthropogenic microhabitats (wall bases, maintained fences, unmaintained fences and hedgerows) along rural-urban gradients in two metropolitan communities (Montréal and Québec, Canada). We hypothesized an impoverishment of flora with increasing levels of urbanization. In each region, we inventoried 90 replicates of each microhabitat distributed along three levels of urbanization. We used multi-factor analysis of variance to compare species richness and functional diversity between local urbanization levels, metropolitan communities and microhabitats. We calculated beta diversity as between-site similarities in composition, and differences were evaluated using a test for homogeneity in multivariate dispersion. No effect of local urbanization level on species richness was observed within Montréal, while reduced richness was found in the most urbanized districts of Québec. In contrast, functional diversity was the highest at a high level of local urbanization. The most urbanized metropolitan community (Montréal) and disturbed microhabitats (wall bases and maintained fences) were usually more species-poor and had lower beta diversity than the less urbanized or disturbed ones. Urbanization level within a metropolitan community influenced beta diversity only in Québec, with different patterns for species (highest at a moderate level) and traits (highest at a high level). Although some of our results support the hypothesis of flora impoverishment with urbanization, plant assemblage responses differed between species and traits, metropolitan communities and microhabitats. Overall, our study emphasizes the need to work at multiple spatial scales and to control for habitat types when examining homogenization processes of flora in urban environments. [ABSTRACT FROM AUTHOR] |
