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. While my research to date has focussed predominantly on the phenotypic responses of animals, I have more recently adopted an evolutionary approach to investigate the adaptive responses of animals to different environmental conditions.
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 on fish, frogs, reptiles and insects.
Evolution of metabolism in Ectotherms
Before an animal can grow and reproduce, it must first survive. The minimum amount of energy an animal needs to survive is estimated by measuring its metabolism while it is at rest. The resting metabolic rate (RMR) of an animal is probably the most widely reported physiological trait in the scientific literature, and is largely determined by an animal’s size. However, for animals of the same size, RMR varies substantially among species, populations and individuals. Why this variation exists has intrigued biologists for decades, but the ultimate factors that drive the evolution of RMR remain controversial. For ectotherms, such as fish and insects, environmental temperature is expected to influence the evolution of RMR because at colder temperatures, RMR slows down. Our meta-analysis of data for fish RMR shows that fish from colder environments have faster RMRs than those from hotter environments, supporting the century-old theory of metabolic cold adaptation. However, my research at Arizona State University with Prof Michael Angilletta, found no support for this theory in fruit flies populations that had evolved in the laboratory under different thermal conditions. I am currently involved in an ongoing study with Prof Craig White at Monash University to test the theory of metabolic cold adaptation in bumblebees in the UK where they are native, and in Australia where they are invasive. Prof White and myself are also involved in ongoing research with A/Prof Michael Kearney at The University of Melbourne to test theories in metabolic ecology by examining the effect of dietary restriction on the relationship between energy use and body mass in Australian skinks. My future research is aimed at investigating the interactive effects of temperature and food availability on the evolution of energy metabolism in animals.
Amphibians and Ultraviolet 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 radiation (UVR) associated with stratospheric ozone depletion is hypothesised to be one of drivers of these mysterious population declines. Our research has examined how amphibians respond to increased UVR exposure while simultaneously being threatened by predators, experiencing high environmental temperatures, living with a large number of conspecifics, or breathing in hypoxic water. This research, largely undertaken as part of my PhD with Prof Craig Franklin, has revealed that examining the effects of UVR in the absence of other ecologically relevant environmental factors can greatly oversimplify and underestimate the effects of UVR 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.
Fish first evolved to breathe the air over 400 million years ago. Breathing air has its 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. Our 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 with Prof Roger Seymour, 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 collaborated with Dr Steven Portugal and Prof Craig White to investigate 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. As a consequence 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 with Dr Qifeng Ye 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.