Invasion hotspots for non‐native plants in Australia under current and future climates

Abstract

We apply the concept of biodiversity hotspot analysis (the identification of biogeographical regions of high species diversity) to identify invasion hotspots -areas of potentially suitable climate for multiple non-native plant speciesin Australia under current and future climates. We used the species distribution model Maxent to model climate suitability surfaces for 72 taxa, recognized as 'Weeds of National Significance' (WoNS) in Australia, under current and projected climate for 2020 and 2050. Current climate suitability layers were summed across all 72 species, and we observed two regions of high climatic suitability corresponding to the top 25th percentile of combined climatic suitability values across Australia. We defined these as potential invasion hotspots. Areas of climatic suitability equivalent to the hotspot regions were identified in the composite maps for 2020 and 2050, to track spatial changes in the hotspots over the two time steps. Two potential invasion hotspot regions were identified under current and projected climates: the south west corner of Western Australia (SW), and south eastern Australia (SE). Herbarium data confirmed the presence of 73% and 99% of those species predicted to be in each hotspot respectively, suggesting that the SE has greater invasion potential. The area of both hotspots was predicted to retract southward and towards the coast under future climate scenarios, reducing in size by 81% (SW) and 71% (SE) by 2050. This reduction was driven by the dominance of southern temperate invasive plant species in the WoNS list (47 of the 72), of which 44 were predicted to experience reductions in their bioclimatic range by 2050. While climate is likely to become less suitable for the majority of WoNS in the future, potential invasion hotspots based on climate suitability are likely to remain in the far south of eastern Australia, and in the far south west of Western Australia by 2050.

Out of the weeds? Reduced plant invasion risk with climate change in the continental United States

“…Global analyses of 99 highly problematic invasive species (plants and animals), have also identified the eastern U.S. as an invasion hotspot with climate change in 2100, with similar northern locations of increased invasion risk (Bellard et al, 2013). Invasion hotspot assessment in Australia showed similar geographic stability despite the differences in species listed (O'Donnell et al, 2012). Together, these studies suggest that the apparent stability in invasion hotspots may be a general pattern with 21st century climate change.…”

“…Range infilling was a species-level metric that represented the proportion of the potential range that was occupied under current climate, calculated for each species as (number of grid cells with observations) / (number of grid cells in potential range) (Bradley et al, 2015). We defined invasion hotspots as areas with potential richness in the top 25th percentile for current and ensemble future climate projections (O'Donnell et al, 2012). Analyses were conducted in R 3.2 (R Core Team, 2015), including the raster package (Hijmans et al, 2015).…”

“…Climate outside of current conditions is possible with climate change (called non-analog climate), so we assessed this possibility in our study region with multivariate environmental similarity surfaces (MESS) (Elith et al, 2011;O'Donnell et al, 2012). MESS analysis measures similarity by comparing the value of each climate variable in each pixel in current climate to the minimum and maximum of future climate for that variable across the continental U.S. (Elith et al, 2010).…”

“…Hotspots of Biological Conservation 203 (2016) [306][307][308][309][310][311][312] plant invasion with current and future climate have been identified in Australia for nationally important invasive plants (Gallagher et al, 2013;O'Donnell et al, 2012), but there has been no comprehensive assessment of the invasion risk posed by plants to the continental U.S. under current and future climates. Invasion risk can have many definitions; this analysis focuses on the geography of invasion risk through invasive plant range characteristics (range infilling) and aggregated range metrics (species richness, invasion debt, and identification of hotspots).…”

Multidimensional biases, gaps and uncertainties in global plant occurrence information

“…Recent advances in unifying global plant taxonomic information (The Plant List, TPL 2014) now allow integrating thousands of floristic data sources under a common taxonomic framework. Potential uses of DAI are manifold (Lavoie 2013), spanning research on diversity patterns (Morueta-Holme et al 2013), biological invasions (O'Donnell et al 2012) or phenological changes (Calinger et al 2013), assessments and monitoring of threats (Brummitt et al 2015), and conservation decision-making (Ferrier 2002;Guisan et al 2013). However, broader application is limited by severe biases in each of the three basic dimensions (Nelson et al 1990;Boakes et al 2010;Schmidt-Lebuhn et al 2013).…”