Rödder D et al. (2017), Global realized niche divergence in the African...

XB-ART-53777

Ecol Evol 2017 May 10;711:4044-4058. doi: 10.1002/ece3.3010.

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Global realized niche divergence in the African clawed frog Xenopus laevis.

Rödder D , Ihlow F , Courant J , Secondi J , Herrel A , Rebelo R , Measey GJ , Lillo F , De Villiers FA , De Busschere C , Backeljau T .

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Although of crucial importance for invasion biology and impact assessments of climate change, it remains widely unknown how species cope with and adapt to environmental conditions beyond their currently realized climatic niches (i.e., those climatic conditions existing populations are exposed to). The African clawed frog Xenopus laevis, native to southern Africa, has established numerous invasive populations on multiple continents making it a pertinent model organism to study environmental niche dynamics. In this study, we assess whether the realized niches of the invasive populations in Europe, South, and North America represent subsets of the species' realized niche in its native distributional range or if niche shifts are traceable. If shifts are traceable, we ask whether the realized niches of invasive populations still contain signatures of the niche of source populations what could indicate local adaptations. Univariate comparisons among bioclimatic conditions at native and invaded ranges revealed the invasive populations to be nested within the variable range of the native population. However, at the same time, invasive populations are well differentiated in multidimensional niche space as quantified via n-dimensional hypervolumes. The most deviant invasive population are those from Europe. Our results suggest varying degrees of realized niche shifts, which are mainly driven by temperature related variables. The crosswise projection of the hypervolumes that were trained in invaded ranges revealed the south-western Cape region as likely area of origin for all invasive populations, which is largely congruent with DNA sequence data and suggests a gradual exploration of novel climate space in invasive populations.

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Species referenced: Xenopus laevis

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References [+] :

Bennett, Thermal dependence of locomotor capacity. 1990, Pubmed

	Figure 1. Density profiles for all environmental variables. Background conditions were extracted within a 200‐km buffer enclosing the native species records.
	Figure 2. Density plots for the four principal components with Eigenvalues >1. Background conditions were extracted within a 200‐km buffer enclosing the native species records. See Table 1 for details
	Figure 3. Four dimensional hypervolumes of the environmental niches of Xenopus laevis as well as for the potential niche within its native distribution characterizing its available climate space.
	Figure 4. Current global distribution (a) and potential distribution of Xenopus laevis as derived from the global hypervolume model trained with the complete set of species records (b)
	Figure 5. Crosswise projection of bdw models (dark blue) and mcp models (light blue) for native and invasive populations. The training area is marked by a blue frame and the respective projection areas can be found within the same row. Blue circles indicate the presence of small areas which are within the hypervolume computed for the training range
	Figure 6. Potential areas of origin of the invasive populations of Xenopus laevis across South Africa (a), as well as predicted ranges based on training regions of North America (b), South America (c), and Europe (d).