Quantifying Phytogeographical Regions of Australia Using Geospatial Turnover in Species Composition

Abstract

The largest digitized dataset of land plant distributions in Australia assembled to date (750,741 georeferenced herbarium records; 6,043 species) was used to partition the Australian continent into phytogeographical regions. We used a set of six widely distributed vascular plant groups and three non-vascular plant groups which together occur in a variety of landscapes/habitats across Australia. Phytogeographical regions were identified using quantitative analyses of species turnover, the rate of change in species composition between sites, calculated as Simpson's beta. We propose six major phytogeographical regions for Australia: Northern, Northern Desert, Eremaean, Eastern Queensland, Euronotian and South-Western. Our new phytogeographical regions show a spatial agreement of 65% with respect to previously defined phytogeographical regions of Australia. We also confirm that these new regions are in general agreement with the biomes of Australia and other contemporary biogeographical classifications. To assess the meaningfulness of the proposed phytogeographical regions, we evaluated how they relate to broad scale environmental gradients. Physiographic factors such as geology do not have a strong correspondence with our proposed regions. Instead, we identified climate as the main environmental driver. The use of an unprecedentedly large dataset of multiple plant groups, coupled with an explicit quantitative analysis, makes this study novel and allows an improved historical bioregionalization scheme for Australian plants. Our analyses show that: (1) there is considerable overlap between our results and older biogeographic classifications; (2) phytogeographical regions based on species turnover can be a powerful tool to further partition the landscape into meaningful units; (3) further studies using phylogenetic turnover metrics are needed to test the taxonomic areas.

A revised area taxonomy of phytogeographical regions within the Australian Bioregionalisation Atlas

“…Since Mueller, there have been several different area taxonomies that may be classified into three distinct groups: vegetations (e.g., Mueller 1858;Diels 1906;Beard 2001), biomes (Byrne et al 2008), and taxonomic/endemic areas or bioregions (Tate 1889, Burbidge 1960, Crisp et al 19951999;Ladiges et al 2011González-Orozco et al 2011, González-Orozco, Ebach et al 2014Stevenson et al 2012; see Ebach 2012 for a detailed history). Of these, the bioregions are of interest as they pertain purely to taxonomic distributions and endemism, which can be quantified independently to other data such as climate and topography using spatial analysis (e.g., Laffan et al 2010).…”

“…Of these, the bioregions are of interest as they pertain purely to taxonomic distributions and endemism, which can be quantified independently to other data such as climate and topography using spatial analysis (e.g., Laffan et al 2010). A recent study by González-Orozco, Ebach et al (2014) has used taxonomic distributions to test existing phytogeographical areas, which have been classified into six regions within the Australian Bioregionalisation Atlas (ABA, Ebach et al 2013). The study by González-Orozco, Ebach et al (2014) used a diverse set of major land plant groups including bryophytes, ferns and several of the largest angiosperm genera and families in Australia (Table 1).…”

“…A recent study by González-Orozco, Ebach et al (2014) has used taxonomic distributions to test existing phytogeographical areas, which have been classified into six regions within the Australian Bioregionalisation Atlas (ABA, Ebach et al 2013). The study by González-Orozco, Ebach et al (2014) used a diverse set of major land plant groups including bryophytes, ferns and several of the largest angiosperm genera and families in Australia (Table 1). The analysis revealed a 65% overlap between their six phytogeographical regions and those of the ABA regions.…”

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AbstractThe phytogeographical regions and sub-regions of Australia are revised in light of new data from a recent analysis by González-Orozco, Ebach et al (2014). The new revision includes two new regions, Northern regio nova and Northern Desert regio nova, and five new sub-regions, Nullarbor sub-regio nova, Central Desert sub-regio nova, Great Sandy Desert Interzone sub-regio nova, Central Queensland sub-regio nova and, Southwestern sub-regio nova.

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“…This new revised version of the phytogeographical regions and sub-regions of Australia's land plants provides an updated classification based on historical nomenclature. The analysis by González-Orozco, Ebach et al (2014) is a biogeographically centered classification that generated the first exclusively taxonomic regionalisation of Australia's land plants, used here to update the ABA phytogeographical regions. …”