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Diversity patterns of seasonal wetland plant communities mainly driven by rare terrestrial species

Abstract

In cleared landscapes, wetlands can represent important reservoirs of native plant diversity, which include terrestrial species. Depending on study aims, non-wetland plants might be removed before analysis, affecting conclusions around biodiversity and community structure. We compared the native plant communities of seasonal wetlands in a predominately agricultural landscape as defined geographically (including all species) with that of the obligate wetland assemblage. We were primarily concerned with determining how this design decision affects ecological and conservation conclusions. We analysed a survey database containing >12,900 flora records from South Australia, developing a new area-based method to remove sampling bias to include only wetlands with a near-complete census. We modelled occupancy, species-area relationships, β-diversity and nestedness under our contrasting community definitions. Terrestrial species were 57.4 % of total richness. Removing these species reduced wetland α-diversity by 45 %, but did not affect the scaling of richness with area (power-law species-area relationship z = 0.21 ± 0.01). Occupancies for wetland plants were relatively uniform, but were heavily dominated by rare (satellite) species when terrestrial plants were included, and this also increased β-diversity. Nestedness for terrestrial species occupancies was marginally lower than predicted under null models, suggesting that rare species often do not co-occur with common species. An implication of these occupancy patterns is that twice as many wetlands (and 50 % more wetland area) would be needed to include every native species within at least one wetland compared with wetland-only species.

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Acknowledgments

We thank R. Duffield, A. Stevens and C. Harding for providing survey data and acknowledge their contributions to wetland biodiversity conservation in South Australia. We also thank the data custodians (C. Miles, The Conservation Council of South Australia and the South Australian State Government) for making data available to D.C.D. Plant functional group assignments were compiled as part of regional water allocation planning for the Mount Lofty Ranges by M. Casanova, J. Nicol and B. Deegan. We thank J. Nicol for making this available.

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Correspondence to David C. Deane.

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The authors declare that they have no conflict of interest.

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Communicated by Dirk Sven Schmeller.

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10531_2016_1139_MOESM1_ESM.pdf

A single PDF file is provided containing six appendices as follows: Appendix 1: data adequacy, survey effort and wetland selection method; Appendix 2: published wetland power-law species-area relationships; Appendix 3: beta-1 index (β 1) of Harrison et al. (1992) calculated using published wetland data; Appendix 4: additional results; Appendix 5: model selection tables; Appendix 6: results of selected analyses with exotic species included (PDF 714 kb)

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Deane, D.C., Fordham, D.A., He, F. et al. Diversity patterns of seasonal wetland plant communities mainly driven by rare terrestrial species. Biodivers Conserv 25, 1569–1585 (2016). https://doi.org/10.1007/s10531-016-1139-1

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  • DOI: https://doi.org/10.1007/s10531-016-1139-1

Keywords

  • β-diversity
  • Biological database
  • Occupancy distribution
  • Species-area relationship
  • Wetland biodiversity