期刊
BASIC AND APPLIED ECOLOGY
卷 9, 期 6, 页码 617-625出版社
ELSEVIER GMBH
DOI: 10.1016/j.baae.2007.11.004
关键词
Biological invasions; Biotic differentiation; Biotic homogenization; California; Exotic species; Flora; Florida; Introduced species; Plants
类别
This study aims to examine the effects of introduced species on increasing (homogenizing) or decreasing (differentiation) floristic similarity of plant composition. We calculated the Jaccard index for each pair of counties within two states of USA. California and Florida. We computed the Jaccard index separately for all (native plus exotic) species, for native species, and for exotic species. We further calculated a homogenization index between all species and native species for each pair of counties by substracting similarity index for native species from that for all species. We correlated the Jaccard and homogenization indices to geographic distance, latitude separation, and longitude separation between pairs of counties and to average human population density and average land area of the two counties. We find a very strong pattern of differentiation for introduced species among nearly all Florida counties. In California, introduces species have a differentiating effect in about half the comparisons. We also find that introduced species tend to have a more homogenizing (or less differentiating effect with increasing distances between counties. Our results do not show a clear relationship between human population density and the homogenization index. (c) 2007 Gesellschaft fur Okologie. Published by Elsevier GmbH. All rights reserved.
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