Distance decay of similarity among European urban floras: the impact of anthropogenic activities on β diversity

• Published in: Global ecology and biogeography Vol. 17; no. 3; pp. 363 - 371
• Main Authors: La Sorte, Frank A, McKinney, Michael L, Pyšek, Petr, Klotz, Stefan, Rapson, G.L, Celesti-Grapow, Laura, Thompson, Ken
• Format: Journal Article
• Language: English
• Published: Oxford, UK Oxford, UK : Blackwell Publishing Ltd 01.05.2008; Blackwell Publishing Ltd; Blackwell Publishing; Blackwell
• Subjects: Animal and plant ecology; Animal, plant and microbial ecology; Anthropogenic activities; archaeophyte; beta diversity; Biogeography; Biological and medical sciences; biotic homogenization; Cities; compositional similarity; Distance decay; Europe; Flora; Fundamental and applied biological sciences. Psychology; General aspects; Introduced species; neophyte; non-native species; Plant ecology; Plants; Species diversity; Synecology; Urban areas; Urban ecology; urban floras; Europe; neophyte; Introduced species; Europe; Biogeography; Homogenization; Beta diversity; Ecology; Urban area; compositional similarity; Anthropogenic activities; biotic homogenization; non-native species; distance decay; Human activity; Flora; Environment impact; urban floras; archaeophyte; Distance; Anthropogenic factor
• ISSN: 1466-822X; 1466-8238
• DOI: 10.1111/j.1466-8238.2007.00369.x

We examine how two categories of non-native species (archaeophyte and neophyte, introduced before and after ad 1500, respectively) have had different impacts on β diversity across European urban floras. Our goal is to use the unique biological perspective provided by urban areas, and the contrasting historical and geographical perspectives provided by archaeophytes and neophytes, to infer how non-native species will impact upon β diversity in the future. Twenty-two urban areas located in seven European countries. We used the β-sim dissimilarity index to estimate the level of β diversity for 231 unique pair-wise combinations of 22 urban floras. We examined bivariate plots of dissimilarity by geographical separation of city centres to evaluate distance decay of similarity for native species, archaeophytes and neophytes. Based on average percentages, 52.8% (SD = 8.2%) of species in the urban floras were identified as non-native with 28.3% (SD = 6.9%) classified as neophytes and 24.5% (SD = 4.9%) as archaeophytes. Relative to native species, across urban floras, archaeophytes were associated with higher compositional similarity and weaker distance decay patterns, whereas neophytes were associated with lower compositional similarity and stronger distance decay patterns. Across European urban floras, archaeophytes and neophytes occurred in similar numbers but archaeophytes were consistently associated with lower β diversity and neophytes with higher β diversity. Thus, the impact of non-native species on β diversity can be determined, at least in part, through their historical and geographical associations with anthropogenic activities. If archaeophytes represent the long-term biogeographical outcome for human commensal species, neophytes could develop similar patterns. The consequences, however, are likely to be more substantial ecologically and geographically due to the increasing numbers of neophytes and their global anthropogenic associations. Nevertheless, at present, our findings suggest that, based on occurrence information, neophytes have not achieved this state with European urban floras retaining regionally distinct assemblages of neophytes.