Imprints of physiological and ecological constraints on the biogeography of an ectotherm

Dr Raquel A. Garcia1,2, Ms Ella E. Morran1,2, Professor Susana Clusella-Trullas1,2

1Department of Botany and Zoology, Stellenbosch University, Stellenbosch, South Africa, 2Centre for Invasion Biology, Stellenbosch, South Africa

Temperature has long been thought to shape species’ geographical distributions. Thermal performance curves derived in the laboratory for ectothermic species are often used to explain the biogeography of species, although with varying success. The realised thermal niches of free-living individuals reflect more than their physiological limits to temperature, also incorporating other abiotic variables as well as ecological factors such as foraging success, predation rates or ontogeny. For a small tortoise endemic to South Africa (Homopus areolatus), we explored laboratory- and field-based thermal performance curves and assessed their ability to predict the species’ distribution limits. In the laboratory, we assessed individuals’ thermal preference and temperature dependence of righting response. In the field, we deployed operative temperature models to describe the thermal landscape available and tracked individuals fitted with light-weight accelerometers and temperature sensors. The data gathered allowed us to examine the individuals’ patterns of activity in relation to selected and available temperatures. Our research sheds light on the roles of physiology and ecology in shaping species’ distributions. By studying two populations in two seasons and along the species’ latitudinal range, including the northern (warmer) limit, our results contribute to improved predictions of species’ vulnerability under climate change.


Raquel A. Garcia is interested in the links between the geography of climate change, the shifting ranges of species, and the organisms’ mechanisms of response to climate change. Working across scales, she uses ecological niche models and climate change metrics to explore biogeographical patterns, and experimental and modelling approaches to investigate the processes at the organismal level that lead to those patterns. Her research has spanned a range of taxonomic groups but her recent work focuses mainly on ectotherms, in particular African herpetofauna. Raquel is currently a postdoctoral fellow at the CLIME Lab at the Botany and Zoology Department of Stellenbosch University, South Africa. More information at

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Species responses to climate change is a rapidly evolving research field, however, much of our progress is being made in independent research areas: e.g. understanding the process vs responding to the implications, terrestrial vs marine ecosystems, global meta-analyses vs in depth species-specific approaches. This interdisciplinary conference develops connections between these parallel streams, and across temporal and spatial scales.

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