Doctoral Degrees (Botany and Zoology)

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Browsing Doctoral Degrees (Botany and Zoology) by Author "Araspin, Laurie Nina"

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    Thermal adaptation in an invasive frog (Xenopus laevis): impact of temperature on locomotion and physiology
    (Stellenbosch : Stellenbosch University, 2024-03) Araspin, Laurie Nina; Measey, John; Herrel, Anthony; Stellenbosch University. Faculty of Science. Dept. of Botany and Zoology.
    ENGLISH ABSTRACT: Life history traits of organisms are modulated by the selective pressures of the environment, generating variation in phenotypes. These different biotic and abiotic factors lead to a diversity of adaptations and the evolution of organismal diversity. This phenotypic diversity can be observed at the interspecific level but also at the intraspecific level in populations living in different environments. Temperature is a characteristic of an animal’s habitat and one of the dimensions of the ecological niche. It is a critical factor impacting all aspects of the biology of organisms, especially in ectotherms. Invasive species are a perfect model to understand the drivers of phenotypic diversity as invasive populations are confronted with novel and potentially contrasting environments compared to those encountered in the native range. Xenopus laevis is an aquatic frog that is invasive on four continents, with invasive populations inhabiting a diversity of environments. The establishment of this species in different climatic regions confirms its great plasticity and/or adaptability. The objective of this thesis was to investigate the thermal adaptation ability of this species that has successfully established in dramatically different thermal environments. Do these animals possess an innate capacity to thrive in novel environments through plasticity or is this success the result of adaptative divergence? The use of thermal performance curves enabled me to assess the relationship between temperature and locomotor and metabolic performance in individuals from different native and invasive populations. Locomotor performance is critical during dispersal, predator escape and prey capture, and is strongly related to the metabolic activity of an organism. In this project, hundreds of individuals were phenotyped. First, the relationship between aquatic and terrestrial locomotion was explored to understand if trade-offs exist between locomotor performance in both environments. Second, locomotor performance depending on temperature in invasive and native populations was assessed to test for possible changes in the thermal dependence of performance among populations. Next, the temperature sensitivity of the metabolic activity was examined in both native and invasive populations. Finally, phenotypes from a F1 generation of the studied populations raised in a common garden environment were compared to the F0 phenotypes. This allows us to understand whether the observed differences among populations are plastic or genetically based. This project has demonstrated that populations exhibit a different thermal dependence of their performance. To predict future invasions, it is essential to understand variability in the thermal adaptation of organisms. Studying traits that contribute to invasion potential can enhance the ability to predict future scenarios of biological invasions. Moreover, variation in performance in individuals of this species depending on temperature provides an insight into how an ectothermic species can survive and cope with different thermal environments, especially in the context of climate change.