In nature, animals contend with numerous abiotic and biotic environmental challenges simultaneously. For instance, animals must cope with variations in temperature and food availability, while also competing with others for resources, avoiding predation and defending against pathogens. Scientific research is often aimed at understanding how these environmental challenges, on their own, affect the ability of animals to survive, grow and reproduce. I, on the other hand, am interested in understanding how animals respond when confronted with multiple environmental challenges simultaneously.
To address this aim, I use laboratory-based experiments to measure the physiological, morphological, behavioural and fitness responses of animals to different environmental challenges alone or in combination. I study how animals respond to these environmental challenges both within their lifetime and after several generations – their phenotypic and adaptive response, respectively.
The outcomes of my research are important for informing policymakers and conservation efforts about how human-mediated environmental change may threaten wildlife.
Please read on for further details of my research.
Energy metabolism and temperature
All animals need energy to live, and the rate at which they produce and use energy is called their metabolic rate. The metabolic rate of animals is linked to their rate of growth and reproduction and their longevity, which are life history traits that determine the success of individuals and populations in challenging environments. In the Anthropocene, animals face many challenges, but I am particularly interested in the consequences of climate warming for ectotherms. Climate warming is expected to increase the energy demands of ectotherms by accelerating their metabolic rates exponentially. However, ectotherms may reduce the thermal sensitivity of their metabolic rates through physiological acclimation and evolutionary adaptation. My research using the fruit fly, Drosophila, shows that metabolic rates do not evolve in response to changes in temperature, but that physiological acclimation can reduce the energetic cost of climate warming. However, my research also demonstrates that other environmental factors, such as diet and species interactions, can modify the metabolic responses of ectotherms to changes in temperatures. This research highlights the importance of studying animal responses to multiple interacting environmental challenges if we are to gain a more accurate appreciation of the threat of climate warming to biodiversity.
Amphibians and Ultraviolet-B radiation
Amphibian populations around the world are disappearing despite the availability of suitable habitat, thus presenting one of the greatest challenges for conservation. Increases in damaging ultraviolet-B radiation (UVBR) associated with stratospheric ozone depletion is hypothesised to be one of drivers of these mysterious population declines. My research has examined how amphibians respond to increased UVBR exposure while simultaneously being threatened by predators, experiencing high environmental temperatures, living at high conspecific density, or breathing in hypoxic water. This research, largely undertaken as part of my PhD, has revealed that examining the effects of UVBR in the absence of other ecologically relevant environmental factors can greatly oversimplify and underestimate the effects of UVBR on amphibians. This research has been used by the Environmental Effects Assessment Panel for the Ozone Secretariat at the United Nations Environment Programme to inform the Parties to the Montreal Protocol and other policymakers on the effects of ultraviolet radiation on human health and the environment.
Mosquitoes and Ultraviolet-B Radiation
Ultraviolet-B radiation (UVBR) is predicted to increase in the tropics by the end of the century due to changes in ozone and cloud cover associated with greenhouse-gas emissions. This is concerning because UVBR modulates immune function in many animals and the tropics is where the burden of human disease is disproportionately high due, in part, to the prevalence of insect disease vectors like mosquitoes. Female mosquitoes are vectors for a range of deadly parasites and viruses that cause diseases like malaria, dengue, chikungunya, Zika, and yellow fever, with dengue regarded as the most important mosquito-borne viral disease globally due to its prevalence and rapid spread. Understanding how mosquito-borne disease risk for humans will change in response to global change is an important challenge for scientists, but the effects of changes in UVBR are largely unknown. In the first study of its kind, I found that exposure to UVBR is detrimental to the fitness of mosquitoes and increases their susceptibility to infection with dengue virus. My research therefore indicates that increased tropical UVBR may have consequences for the future socioeconomic burden of mosquito-borne diseases.
Air-breathing fish
Fish first evolved to breathe the air over 400 million years ago. Breathing air has advantages over breathing water – air tends to have more oxygen and is easier to ventilate compared to water. However, breathing air while living in water has it complications, one being knowing when to swim to the surface to take a breath. Going to the water’s surface exposes air-breathing fish to predators and interrupts other important activities such as finding food or a mate. My research has explored some of the strategies that air-breathing fish employ to balance the advantages of breathing air against the disadvantages of going to the surface. For my Honours research, I examined whether pearl gouramis are able to sense the amount of oxygen in their air-breathing organ, so that they might know when to replenish their store of air. Following my PhD, I investigated how male Siamese fighting fish manage to breathe air while simultaneously engaging in aggressive competitions with other males.
fish salinity tolerances
Many rivers in Australia, including the Murray-Darling Basin, have had their flows regulated through the construction of dams and weirs. Because of this regulation, rising salinity levels have become a major issue for the Murray-Darling that threatens the health of native fish populations. Fish health is recognised as a key indicator of broader ecological health. Therefore, environmental flow strategies often include setting salinity and water quality targets to achieve positive outcomes for fish. Following my undergraduate studies, I worked for the South Australian Government at the South Australian Research and Development Institute. There I was involved in research that assessed the salinity and water quality tolerances of the eggs, larvae and juveniles of native and exotic fish species that live in the Lower River Murray. At the time of our research, management guidelines relied on generalised adult salinity tolerance thresholds. However, based on our research, it was recommended that these thresholds be lowered to account for the lower salinity tolerances of the earlier life stages of the native fish, and to ensure the sustainability of their populations. You can find a copy of the report here.
