Contrasting environments shape thermal physiology across the spatial range of the sandhopper Talorchestia capensis
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Integrating thermal physiology and species range extent can contribute to a better understanding of the likely effects of climate change on natural populations. Generally, broadly distributed species show variation in thermal physiology between populations. Within their distributional ranges, populations at the edges are assumed to experience more challenging environments than central populations (fundamental niche breadth hypothesis). We have investigated differences in thermal tolerance and thermal sensitivity under increasing/decreasing temperatures among geographically separated populations of the sandhopper Talorchestia capensis along the South African coasts. We tested whether the thermal tolerance and thermal sensitivity of T. capensis differ between central and marginal populations using a non-parametric constraint space analysis. We linked thermal sensitivity to environmental history by using historical climatic data to evaluate whether individual responses to temperature could be related to natural long-term fluctuations in air temperatures. Our results demonstrate that there were significant differences in the thermal response of T. capensis populations to both increasing/decreasing temperatures. Thermal sensitivity (for increasing temperatures only) was negatively related to temperature variability and positively related to temperature predictability. Two different models fitted the geographical distribution of thermal sensitivity and thermal tolerance. Our results confirm that widespread species show differences in physiology among populations by providing evidence of contrasting thermal responses in individuals subject to different environmental conditions at the limits of the species’ spatial range. When considering the complex interactions between individual physiology and species ranges, it is not sufficient to consider mean environmental temperatures, or even temperature variability; the predictability of that variability may be critical.
KeywordsMacrophysiology ACH Thermal sensitivity Climatic variability Climate change Temperature predictability
The authors thank two anonymous reviewers for their valuable comments on earlier drafts of this manuscript. We are grateful to Dr. M. Tagliarolo for her contribution to the experiments and Dr. Irene Ortolani for her help composing the first draft of the paper. The authors also thank the South African Weather Service (http://www.weathersa.co.za ) for the release of historical climatic dataset. This paper was written under the framework of the project ‘‘CREC’’ [EU IRSES#247514]. The work is based upon research supported by the South African Research Chairs Initiative of the Department of Science and Technology and National Research Foundation of South Africa (NRF).
Author contribution statement
SB, FP and MF conceived the ideas. SB and MF designed and performed the experiments. SB, NFW, MF, SC analysed the data. SB, NFW, CDM and FP wrote the manuscript.
Compliance with ethical standards
Conflict of interest
The authors declare no competing financial interests or any other form of conflict of interest
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