Ecophysiological Specialisation of Short-Range & Widespread Gehyra Species

The geographic range size of a species has been identified as a key predictor for extinction risk. Range size is positively correlated with niche breadth, meaning generalist species are expected to have larger distributions than specialists and are therefore less susceptible to pressures including habitat loss and climate change. Specialised species with small geographic ranges can compensate for this high extinction risk by having high local abundance despite scarcity over broader geographic scales. Refugial sites can facilitate species persistence by providing a stable, favourable climate over large time-scales despite high climatic variability in surrounding areas. These refugial sites are expected to lead to narrower climatic tolerances in species, which are assumed to specialise to capitalise on their stable climatic niche. Conversely, species which are not restricted to refugial sites are likely to experience a greater climate variability over time and must be capable of tolerating a broader range of environmental conditions and quickly adapting to environmental changes.
The primary aim of this project is to identify whether geckos of genus Gehyra (commonly known as dtellas), differ in their levels of physiological specialisation in relation to their distribution and habitat types. Species are classified as either short-range-endemics (SREs)- species with limited distribution, restricted to refugial habitats with historically stable climates- or widespread (W)- species with broad distributions and found in habitats with variable environmental conditions. The comparison of SRE versus W species will also involve contrasting species from arid and mesic climate zones to identify potential differences in their physiology associated with broader climatic conditions. Additionally, the physiological response of species to temporal climatic patterns will be investigated, with consideration of variance in climatic parameters across broad (seasonal) and narrow (daily) temporal scales and how these fluctuations differ between climate zones. It is predicted that species restricted to refugia will exhibit higher levels of physiological specialisation, narrower climate tolerances, and lower plasticity in these measures than sympatric relatives with widespread distributions.