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The varying role of population abundance in structuring indices of biotic homogenization

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Abstract:

Abstract Aim 

An important component of human-induced global change is the decrease or increase in community distinctiveness (taxonomic homogenization or differentiation, respectively) that follows the loss of native species and gain of non-native species. We use simulation approaches to assess the extent to which conclusions about the outcome of the homogenization process depend on whether or not abundance data are incorporated. Location 

Data were produced through computer simulation. Methods 

The frequency with which occurrence-based similarity indices and abundance-based similarity indices give different views of changes in community similarity, and the conditions under which such differences occurred were assessed using both deterministic and stochastic modelling approaches to simulate species assemblage states. Results 

Occurrence-based and abundance-based indices were positively correlated across the set of simulations for both the deterministic and stochastic models. However, in both situations approximately one quarter (25%) of models resulted in contrasting outcomes for the two approaches of calculating changes in compositional similarity; that is, one data type showed a positive value (homogenization), whereas the other showed a negative value (differentiation). Main conclusions 

In the majority of cases, species abundances will not change drastically enough after perturbation to produce large differences between homogenization scores measured using occurrence versus abundance information. However, in cases where these changes are large, it is important to recognize that the choice of metric to analyse homogenization trends will influence the qualitative and quantitative conclusions drawn. Studies of real assemblages are therefore necessary to evaluate the role of species abundance in defining the magnitude and direction of changes in community composition across space, and the implications of these changes for native biodiversity.

Keywords: Biotic homogenization; Bray–Curtis index; Sørensen index; compositional similarity; extirpation; introduction

Document Type: Research Article

DOI: https://doi.org/10.1111/j.1365-2699.2007.01827.x

Affiliations: 1: Ecology, Evolution and Natural Resources, Rutgers University, 14 College Farm Road, North Brunswick, NJ 08901, USA 2: School of Aquatic and Fishery Sciences, University of Washington, Box 355020, Seattle, WA 98195, USA 3: Institute of Zoology, Zoological Society of London, Regent's Park, London NWI 4RY, UK

Publication date: 2008-05-01

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