Invasiveness and homogenization: synergism of wide dispersal and high local abundance

Authors: McKinney, Michael L.; La Sorte, Frank A.

Source: Global Ecology & Biogeography, Volume 16, Number 3, May 2007 , pp. 394-400(7)

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Abstract:

Aim

To determine whether invasive and locally abundant non-native species have a more homogenizing effect on plant communities than non-invasive and less abundant non-native species. Location

California and Florida counties, conservation areas in the USA, and eight US cities. Methods

Species lists among counties, conservation areas and cities were compared to see whether invasive and abundant non-native species increased the Jaccard index of similarity between localities beyond any increases caused by non-invasive and less abundant non-native species. Results

For all comparisons, we found that invasive non-native species have a significantly greater homogenizing effect than non-invasive non-native species. For the US conservation areas, we found that locally abundant invasive species tend to be more widespread and more widely shared than less abundant invasive species. There is also a positive relationship between homogenization by invasive species and the magnitude of human disturbance. Main conclusions

Invasive non-native species tend to be disproportionately shared among communities relative to non-invasive non-native species. This effect is enhanced by human disturbance, as measured by the ratio of non-native to native species. There is a synergism between abundance and geographical range which enhances the homogenizing effects of abundant species. Invasive species, with wide ecological niches, are more widely shared among communities and more locally abundant. Abundant invasive species are thus more spatially homogenizing, and more ecologically dominant (functionally homogenizing). Also, `perceived homogenization' is probably greater than homogenization measured by the increase in shared species. The abundant species typically seen by the casual observer in a biological community are probably more commonly shared between communities than less common species. Studies that lack abundance data and measure homogenization only on the basis of shared species, which includes most homogenization studies to date, probably underestimate the homogenizing impacts of non-native species as perceived by people.

Keywords: Biotic homogenization; exotic species; invasive species; native species; plants; USA

Document Type: Research article

DOI: http://dx.doi.org/10.1111/j.1466-8238.2007.00296.x

Affiliations: 1: Department of Fisheries and Wildlife Sciences, University of Missouri, Columbia, MO 65211, USA

Publication date: 2007-05-01

Invasiveness and homogenization: synergism of wide dispersal and high local abundance

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