Assessing the effects of climate change on distributions of Cape Floristic Region amphibians

Abstract

Climatic changes have had profound impacts on species distributions throughout time. In response, species have shifted ranges, adapted genetically and behaviourally or become extinct. Using species distribution models, we examined how changes in suitable climatic space could affect the distributions of 37 endemic frog species in the Cape Floristic Region (CFR) – an area proposed to have evolved its megadiversity under a stable climate, which is expected to change substantially in future. Species distributions were projected onto mean climate for a current period (1950 to 2000), hindcasted to palaeoclimate (Last Glacial Maximum; LGM ≈ 21 kya and Holocene Glacial Minimum; HGM ≈ 6 kya) and forecasted for two emissions scenarios (A2a and B2a) for the year 2080. We then determined the changes in area sizes, direction (longitude and latitude), fragmentation index and biotic velocity, and assessed if these were affected by life-history traits and altitude. We found that the biotic velocity at which the CFR amphibian community is expected to shift north (A2a ≈ 540.5 km/kya) and east (B2a ≈ 198 km/kya) far exceeds historical background rates (≈1.05 km/kya, north and west ≈ 2.36 km/kya since the LGM). Our models further suggest that the CFR amphibian community has already lost about 56% of suitable climate space since the LGM and this loss is expected to accelerate under future emission scenarios (A2a ≈ 70%; B2a ≈ 60%). Lastly, we found that highland species were more fragmented than lowland species between the LGM and current period, but that the fragmentation of lowland species between current and future climates is expected to increase.

Global realized niche divergence in the African clawed frog Xenopus laevis

“…() observed significant acclimation effects on swimming velocity, suggesting a pre‐adaptation capacity to cooler environments, which may partly explain the invasion success of X. laevis in Europe. However, SDM projections of a broad range of different South African amphibian species on paleoclimate scenarios revealed only marginal shifts in potential distributions under last glacial maximum conditions (Mokhatla, Rödder, & Measey, ; Schreiner, Rödder, & Measey, ) suggesting an overall limited probability of a historic pre‐adaption to cooler environments. A first mechanism involving evolutionary changes would be an establishment of the initial invasive populations in climates similar to the environmental conditions within the area of origin and subsequent adaptation and niche expansion. This scenario is supported by the finding that the invasive populations in, for example, Chile originated from a single introduction and show a signature of a recent bottleneck and are genetically very similar indicating a rapid spread from a small source population (Lobos et al., ).…”

“…However, SDM projections of a broad range of different South African amphibian species on paleoclimate scenarios revealed only marginal shifts in potential distributions under last glacial maximum conditions (Mokhatla, Rödder, & Measey, 2015;Schreiner, Rödder, & Measey, 2013) suggesting an overall limited probability of a historic pre-adaption to cooler environments.…”

Peer Review #2 of "The role of ambient temperature and body mass on body temperature, standard metabolic rate and evaporative water loss in southern African anurans of different habitat specialisation (v0.1)"

“…They may also provide us with a snapshot of how physiological differences drive species-specific responses to climate change. Climate change is expected to be more pronounced in sub-Saharan Africa with increased drying, particularly in the winter rainfall region and less variable rainfall regimen across the region (Giannini et al, 2008;Engelbrecht, Engelbrecht & Dyson, 2013), further placing amphibians of this region at high risk of extinction (Hof et al, 2011;Foden et al, 2013;Garcia et al, 2014;Mokhatla et al, 2015). Southern Africa has a diverse anuran fauna occupying many different habitat types (Alexander et al, 2004), and we may expect variation in the way each species will respond to environmental challenges in their respective environments (Loveridge, 1976).…”

The role of cultural norms in shaping attitudes towards amphibians in Cape Town, South Africa

“…Climate change is an emerging land-cover change driver. Predictions indicate shifts in natural habitats 80 years hence will occur at rates 500 times faster than current trends [14]. In short, amphibian species are threatened globally by a changing world and these changes are anthropogenic.…”