My research focus is on marine megafauna ecology, primarily looking at the effects of climate change on local adaptation and population dynamics.
The main focus of my PhD thesis (completed Aug 2018) was to determine how climate change will impact the development of sea turtles in Western Australia. In particular, in examined how rising ambient temperatures will influence the sex-ratios and embryonic mortality of flatback (Natator depressus) and green (Chelonia mydas) sea turtles at rookeries throughout the Kimberley and Pilbara region of WA. This research entailed three separate, yet interlinking projects. Initial steps involved developing the NicheMapR (Kearney & Porter, 2017) microclimate model to perform at predicting below-surface sand temperatures on Australian beaches. This research was published in the Journal of Thermal Biology (see Publications), and demonstrated a high correspondence between predicted and observed sand temperatures, thus validating its' use for predictive studies.
Due to the high levels of philopatry exhibited by sea turtles, populations are expected to be locally adapted to thermal environments at rookeries. The second component of my thesis compared development rates (and inferred thermal tolerances), as well as parameters defining the temperature-dependent sex determination (TSD) reaction norm parameters between and within the species. These parameters varied greatly within N. depressus, suggesting that while some populations (e.g. Cape Domett) have adapted to warming climates by shifting nesting phenology to cooler periods, others (such as Eighty Mile Beach) have undergone evolution of the sex-determining mechanism to ensure production of mixed sexes. This research is currently (April 2020) under review in Functional Ecology.
To assess how climate change will impact these populations, the third aspect of my thesis was to integrate the mechanistic microclimate model with the population-specific thermal thresholds. I applied a suite of climate change scenarios (low to high emission scenarios) to macro-scale climate inputs for NicheMapR and ran models for future scenarios (2030, 2050, 2070 and 2090). My results suggest populations will be differentially impacted by climate change due to existing and future environmental heterogeneity, spatially explicit changes in climate, and existing differences in thermal thresholds, coupled with differences in nesting phenology. In brief, the results showed that winter nesting populations of N. depressus are at the greatest risk of rising ambient temperatures as they lack the ability to shift nesting to a cooler time of year. Should summer nesting populations also be unable to shift nesting phenology, or shift nesting ranges polewards, they are also at risk of local extinctions. Management plans should therefore consider sea turtles at a population-level to ensure continued survival of these species. This component is still in preparation for publication.
My postdoctoral study at the Florida Atlantic University aimed to assess how anomalous scute (carapace and plastron scales) development may impact individual survival. Using a 25-year photo data set, we explore how the prevalence of scute anomalies fluctuates within populations of sea turtle as they grow. We compared frequencies of anomalies with the size of loggerhead (Caretta caretta) and green (Chelonia mydas) sea turtles captured off the east coast of Florida. Our findings suggest that anomalous scute arrangements have no survival costs for individuals, with frequencies remaining fairly consistent of the size range of our individuals (~20 - 120cm). The findings of this study were published in the Journal of Morphology in 2021.