Phylogenetic tests of community assembly across regional to continental scales in tropical and subtropical rain forests

Authors

  • Robert Kooyman,

    Corresponding author
    1. Department of Biological Sciences, Macquarie University, NSW 2109, Australia
    2. National Herbarium of New South Wales, Botanic Gardens Trust, Mrs Macquaries Road, Sydney, NSW 2000, Australia
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  • Maurizio Rossetto,

    1. National Herbarium of New South Wales, Botanic Gardens Trust, Mrs Macquaries Road, Sydney, NSW 2000, Australia
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  • William Cornwell,

    1. Biodiversity Research Centre, University of British Columbia, 6270 University Blvd, Vancouver BC V6T IZ4, Canada
    2. Department of Integrative Biology, University of California, Berkeley, CA 94720, USA
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  • Mark Westoby

    1. Department of Biological Sciences, Macquarie University, NSW 2109, Australia
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Robert Kooyman, Department of Biological Sciences, Macquarie University, Sydney NSW 2109, Australia. E-mail: robert.kooyman@mq.edu.au; robert@ecodingo.com.au

ABSTRACT

Aim  To measure and quantify community phylogenetic structure to evaluate how evolutionary, ecological and biogeographic processes have shaped the distributions and assemblage of tropical and subtropical rain forest tree species across local, regional and continental scales.

Location  Australia.

Methods  We used 596 assemblage-level samples and 1137 woody species in rain forest vegetation sampled across two latitude regions (tropics and sub-tropics) and five distinct areas. Based on this dataset, we obtained and analysed species-level trait values (for leaf size, seed size, wood density and maximum height at maturity), measures of community phylogenetic structure and species turnover across space (beta) and evolutionary time (phylobeta).

Results  Phylobeta values showed that at continental scales (i.e. across the latitude regions combined) species replacement, as turnover in assemblages through time, was by more phylogenetically distant (i.e. less closely related) taxa. Within latitude regions replacement was by more closely related taxa. Assemblages of species were more phylogenetically clustered across the whole phylogeny (net relatedness index) and with respect to more recent divergences (nearest related taxon index) where the effects of historic disturbance (climatic oscillations) had been greater, and less clustered in long-term stable (refugial) locations. Local species composition in the stable wet tropics showed significant phylogenetic evenness, but there was no corresponding evenness in distributions of the ecological traits measured.

Main conclusions  Despite a shared evolutionary and biogeographic history, the two regions diverged from each other before the development of internal divergences. Phylogenetic evenness is more evident in long-term stable habitats (refugia) where species interact in conserved niches. Phylogenetic clustering is more evident where recolonization of more highly disturbed areas from historically reduced species pools reflects filtering of species into phylogenetically preferred habitats.

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