Linking biotic homogenization to habitat type, invasiveness and growth form of naturalized alien plants in North America

Authors

  • Hong Qian,

    Corresponding author
    1. Research and Collections Center, Illinois State Museum, Springfield, IL 62703, USA
      Hong Qian, Research and Collections Center, Illinois State Museum, Springfield, IL 62703, USA.
      E-mail: hqian@museum.state.il.us
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  • Qinfeng Guo

    1. USDA-Southern Research Station, Asheville, NC 28804, USA
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Hong Qian, Research and Collections Center, Illinois State Museum, Springfield, IL 62703, USA.
E-mail: hqian@museum.state.il.us

Abstract

Aim  Biotic homogenization is a growing phenomenon and has recently attracted much attention. Here, we analyse a large dataset of native and alien plants in North America to examine whether biotic homogenization is related to several ecological and biological attributes.

Location  North America (north of Mexico).

Methods  We assembled species lists of native and alien vascular plants for each of the 64 state- and province-level geographical units in North America. Each alien species was characterized with respect to habitat (wetland versus upland), invasiveness (invasive versus non-invasive), life cycle (annual/biennial versus perennial) and habit (herbaceous versus woody). We calculated a Jaccard similarity index separately for native, for alien, and for native and alien species. We used the average of Jaccard dissimilarity index (1 − Jaccard index) of all paired localities as a measure of the mean beta diversity of alien species for each set of localities examined in an analysis. We used a homogenization index to quantify the effect of homogenization or differentiation.

Results  We found that (1) wetland, invasive, annual/biennial and herbaceous alien plants markedly homogenized the state-level floras whereas non-invasive and woody alien plants tended to differentiate the floras; (2) beta diversity was significantly lower for wetland, invasive, annual/biennial and herbaceous alien plants than their counterparts (i.e. upland, non-invasive, perennial and woody alien plants, respectively); and (3) upland and perennial alien plants each played an equal role in homogenizing and differentiating the state-level floras.

Main conclusions  Our study shows that biotic homogenization is clearly related to habitat type (e.g. wetland versus uplands), species invasiveness and life-history traits such as life cycle (e.g. annual/biennial and herbaceous versus woody species) at the spatial scale examined. These observations help to understand the process of biotic homogenization resulting from alien vascular plants in North America.

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