Phylogenetic patterns differ for native and exotic plant communities across a richness gradient in Northern California

Authors

  • Marc W. Cadotte,

    Corresponding author
    1. National Center for Ecological Analysis and Synthesis, University of California, 735 State St., Santa Barbara, CA 93101, USA
    2. Department of Biological Sciences, University of Toronto, Scarborough, 1265 Military Trail, Scarborough, ON, Canada M1C 1A4
      Correspondence: Marc W. Cadotte, Department of Biological Sciences, University of Toronto, Scarborough, 1265 Military trail, Scarborough, ON, Canada M1C 1A4.
      E-mail: mcadotte@utsc.utoronto.ca
    Search for more papers by this author
  • Elizabeth T. Borer,

    1. Department of Ecology, Evolution and Behavior, University of Minnesota, 1987 Upper Buford Circle, St. Paul, MN 55108, USA
    Search for more papers by this author
  • Eric W. Seabloom,

    1. Department of Ecology, Evolution and Behavior, University of Minnesota, 1987 Upper Buford Circle, St. Paul, MN 55108, USA
    Search for more papers by this author
  • Jeannine Cavender-Bares,

    1. Department of Ecology, Evolution and Behavior, University of Minnesota, 1987 Upper Buford Circle, St. Paul, MN 55108, USA
    Search for more papers by this author
  • W. S. Harpole,

    1. Ecology, Evolution and Organismal Biology, Iowa State University, Ames, IA 50011, USA
    Search for more papers by this author
  • Elsa Cleland,

    1. Ecology, Behavior and Evolution, University of California, San Diego, La Jolla, CA 92093, USA
    Search for more papers by this author
  • Kendi F. Davies

    1. Department of Ecology and Evolutionary Biology, University of Colorado, Boulder, CO 80309, USA
    Search for more papers by this author

Correspondence: Marc W. Cadotte, Department of Biological Sciences, University of Toronto, Scarborough, 1265 Military trail, Scarborough, ON, Canada M1C 1A4.
E-mail: mcadotte@utsc.utoronto.ca

Abstract

Aim  Increasingly, ecologists are using evolutionary relationships to infer the mechanisms of community assembly. However, modern communities are being invaded by non-indigenous species. Since natives have been associated with one another through evolutionary time, the forces promoting character and niche divergence should be high. On the other hand, exotics have evolved elsewhere, meaning that conserved traits may be more important in their new ranges. Thus, co-occurrence over sufficient time-scales for reciprocal evolution may alter how phylogenetic relationships influence assembly. Here, we examined the phylogenetic structure of native and exotic plant communities across a large-scale gradient in species richness and asked whether local assemblages are composed of more or less closely related natives and exotics and whether phylogenetic turnover among plots and among sites across this gradient is driven by turnover in close or distant relatives differentially for natives and exotics.

Location  Central and northern California, USA.

Methods  We used data from 30 to 50 replicate plots at four sites and constructed a maximum likelihood molecular phylogeny using the genes: matK, rbcl, ITS1 and 5.8s. We compared community-level measures of native and exotic phylogenetic diversity and among-plot phylobetadiversity.

Results  There were few exotic clades, but they tended to be widespread. Exotic species were phylogenetically clustered within communities and showed low phylogenetic turnover among communities. In contrast, the more species-rich native communities showed higher phylogenetic dispersion and turnover among sites.

Main conclusions  The assembly of native and exotic subcommunities appears to reflect the evolutionary histories of these species and suggests that shared traits drive exotic patterns while evolutionary differentiation drives native assembly. Current invasions appear to be causing phylogenetic homogenization at regional scales.

Ancillary