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

Authors

  • Frank A. La Sorte,

    Corresponding author
    1. Division of Biological Sciences, University of California, San Diego, La Jolla, CA 92093, USA,
      *Correspondence: Frank A. La Sorte, Ecology, Behavior and Evolution Section, Division of Biological Sciences, University of California, San Diego, 9500 Gilman Drive, MC 0116, La Jolla, CA 92093, USA. E-mail: flasorte@ucsd.edu
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  • Michael L. McKinney,

    1. Department of Earth and Planetary Sciences, University of Tennessee, Knoxville, TN 37996, USA,
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  • Petr Pyšek,

    1. Institute of Botany, Academy of Sciences of the Czech Republic, CZ-252 43 Průhonice, Czech Republic,
    2. Department of Ecology, Faculty of Science, Charles University, Viničná 7, CZ-128 01 Praha 2, Czech Republic,
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  • Stefan Klotz,

    1. UFZ – Helmholtz Centre for Environmental Research, Department of Community Ecology (BZF), Theodor-Lieser-Strasse 4, D-06120 Halle, Germany,
    2. Virtual Institute for Macroecology, Theodor-Lieser-Strasse 4, D-06120 Halle, Germany,
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  • G.L. Rapson,

    1. Ecology Group, Institute of Natural Resources, Massey University, Palmerston North, New Zealand,
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  • Laura Celesti-Grapow,

    1. Department of Plant Biology, Sapienza University of Rome, Piazzale Aldo Moro 5, I-00185, Rome, Italy,
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  • Ken Thompson

    1. Department of Animal and Plant Sciences, University of Sheffield, Sheffield S10 2TN, UK
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*Correspondence: Frank A. La Sorte, Ecology, Behavior and Evolution Section, Division of Biological Sciences, University of California, San Diego, 9500 Gilman Drive, MC 0116, La Jolla, CA 92093, USA. E-mail: flasorte@ucsd.edu

ABSTRACT

Aim  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.

Location  Twenty-two urban areas located in seven European countries.

Methods  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.

Results  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.

Main conclusions  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.

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