Quantifying Phytogeographical Regions of Australia Using Geospatial Turnover in Species Composition

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

Non-geographic collecting biases in herbarium specimens of Australian daisies (Asteraceae)

Biological collections are increasingly becoming databased and available for novel types of study. A possible limitation of these data, which has the potential to confound analyses based on them, is their biased composition due to non-random and opportunistic collecting efforts. While geographic biases are comparatively well studied and understood, very little attention has been directed at other potential biases. We used Asteraceae specimen data from Australia’s Virtual Herbarium to test for over- and under-representation of plants with specific morphology, phenology and status by comparing observed numbers of specimens against a null distribution of simulated collections. Strong collecting biases could be demonstrated against introduced plants, plants with green or brown inflorescences, and very small plants. Specimens belonging to species with very restricted areas of distribution were also found to be strongly underrepresented. A moderate bias was observed against plants flowering in summer. While spiny plants have been collected only about half as often as should be expected, much of this bias was due to nearly all of them also being introduced (thistles). When introduced species were analyzed alone, a negative effect of spines remained but was much more moderate. The effect of woody or herbaceous habit, other inflorescence colours, tall growth and size of the capitula was comparatively negligible. Our results indicate that care should be taken when relying on specimen databases or the herbaria themselves for studies examining phenology, resource availability for pollinators, or the distribution and abundance of exotic species, and that researchers should be aware of collecting biases against small and unattractively coloured plants

Continental‐scale spatial phylogenetics of Australian angiosperms provides insights into ecology, evolution and conservation

Aim Biodiversity studies typically use species, or more recently phylogenetic diversity (PD), as their analysis unit and produce a single map of observed diversity. However, observed biodiversity is not necessarily an indicator of significant biodiversity and therefore should not be used alone. By applying a small number of additional metrics to PD, with associated statistical tests, we can determine whether more or less of the phylogeny occurs in an area, whether branch lengths in an area are longer or shorter, and whether more long or short-branched endemism occurs in an area, than expected under a null model. Location Australian continent. Methods We used a phylogeny sampling 90% of Australia's angiosperm genera, and 3.4 million georeferenced plant specimens downloaded from Australia's Virtual Herbarium (AVH), to calculate PD, relative phylogenetic diversity (RPD) and relative phylogenetic endemism (RPE). Categorical analysis of neo- and palaeo-endemism (CANAPE) and randomization tests were performed to determine statistical significance. Results We identify several combinations of significant PD and endemism across the continent that are not seen using observed diversity patterns alone. Joint interpretation of these combinations complements the previous interpretations of Australia's plant evolutionary history. Of conservation concern, only 42% of the significant endemism cells found here overlap with existing nature reserves. Main conclusions These spatial phylogenetic methods are feasible to apply to a whole flora at the continental scale. Observed richness or PD is inadequate to fully understand the patterns of biodiversity. The combination of statistical tests applied here can be used to better explain biodiversity patterns and the evolutionary and ecological processes that have created them. The spatial phylogenetic methods used in this paper can be also be used to identify conservation priorities at any geographical scale or taxonomic level

Phylogenetic approaches reveal biodiversity threats under climate change

Predicting the consequences of climate change for biodiversity is critical to conservation efforts. Extensive range losses have been predicted for thousands of individual species, but less is known about how climate change might impact whole clades and landscape-scale patterns of biodiversity. Here, we show that climate change scenarios imply significant changes in phylogenetic diversity and phylogenetic endemism at a continental scale in Australia using the hyper-diverse clade of eucalypts. We predict that within the next 60 years the vast majority of species distributions (91%) across Australia will shrink in size (on average by 51%) and shift south on the basis of projected suitable climatic space. Geographic areas currently with high phylogenetic diversity and endemism are predicted to change substantially in future climate scenarios. Approximately 90% of the current areas with concentrations of palaeo-endemism (that is, places with old evolutionary diversity) are predicted to disappear or shift their location. These findings show that climate change threatens whole clades of the phylogenetic tree, and that the outlined approach can be used to forecast areas of biodiversity losses and continental-scale impacts of climate change

The plant groups used in this study, number of occurrence points, and the number of species per group, with the totals.

<p>The plant groups used in this study, number of occurrence points, and the number of species per group, with the totals.</p

Environmental variables used in our analyses.

<p>Environmental variables used in our analyses.</p

Phytogeographical regions of Australian terrestrial flora (a) as defined by the corresponding dendrogram (b).

<p>The colors of the regions in the map correspond to those used to plot the dendrogram. The dendrogram is a representation of the spatial relationship of dissimilarities in species composition among regions.</p

Glossary of terms.

<p>The terms, regions, areas, and vegetation are often used inter-changeably, however, they do have specific meanings that we use herein with the following definitions.</p

Phytogeographical regions and new subregions proposed for Australia (a), and their corresponding dendrogram (b).

<p>Note that the colors of the dendrogram clusters correspond to the colors of the subregions. Shaded colors indicate relationships: light blue and dark blue cluster together before clustering with brown colours.</p

Gi* spatial statistics for the six phytogeographical regions of Australian flora. Bolded means statistically significant (α = 0.05).

<p>N =  number of grid cells per region. Underlined values are the most extreme scores for each region.</p