Marine capture-fisheries have expanded ten-fold over the past few decades leading to severe decline in fish stocks as well as populations of non-target or ‘bycatch’ species, which comprise ~ 40% of global catch. Large-bodied, slow growing species, like elasmobranchs, cetaceans, and sea turtles, referred to as marine megafauna, which generally occupy higher trophic levels, are perhaps most severely affected by such mortality. At least 160 species of elasmobranchs and 25 species of cetaceans have been recorded from Indian waters, several of which are regularly caught in fisheries. However, information on them is limited to their catch rates with little data on the drivers of their bycatch. Incidental mortality of cetaceans is even more challenging to record since all species are protected by law and bycatch is discarded at sea.  For my research, I propose to understand how the spatial and temporal patterns of fisheries impact marine megafauna in Indian waters, and to what extent may these be explained by ecological and anthropogenic factors. The chapters of my thesis focus on a) Combining fish-landing site surveys with spatial information on multi-gear fisheries to understand bycatch risk of elasmobranchs at two contrasting locations i.e., Malvan and Visakhapatnam on the west and east coast of India, respectively to test whether bycatch patterns can be generalised across environments, b) testing novel methods to combine oceanographic particle tracking with hierarchical modelling to quantify and elucidate the broader drivers of cetacean bycatch using ocean circulation, remote sensing, and stranding data across India; and c) understanding the behaviour of Indian Ocean humpback dolphins around fishing vessels to explore specific mechanisms of bycatch in Goa, potentially using drone based surveys.   For my first chapter, I have sampled more than 1500 fishing vessels across two seasons at both sites. Gear use and diversity are similar across the sites, but species composition and catch-rates differ. For my second chapter, preliminary results using dead cetacean stranding data from Goa suggest that between 2 - 4 small cetaceans may be dying off its coast per 100 km2 per year, of which at least 30% may be due to bycatch in fishing gear. Altogether, the results of my thesis will elaborate on how and why megafauna species are susceptible to bycatch and help develop plans for species conservation and fisheries management. 

Passive Acoustic Monitoring (PAM) has emerged as a possible alternative to traditional field surveys, which are tedious, expensive, and often limited to a few sites. Although PAM eases collection of data, the sheer volume of data generated complicates the analysis process. Recently, researchers have simplified the analysis process by using soundscape-based machine learning models that can extract information such as species richness and occurrence from audio data. But most of these methods either fail to generalize to various landscapes and across anthropogenic gradients or have not been tested in such environments. Thus, for my first objective, I will develop soundscape-based methods to determine habitat quality across different tropical landscapes. I aim to collect audio data across different tropical habitats along a gradient of land use and test the performance of current soundscape-based models and build better generalizable models. Soundscape-based methods have also been able to track spatiotemporal avian biodiversity patterns in temperate climates at coarser timescales and infer species occurrence. Thus, for my second objective, I will test if we can use these methods to track avian spatiotemporal biodiversity patterns at finer timescales in tropical habitats, and if we can use soundscapes to predict presence of non-vocalizing species. I aim to collect fine scale audio data along with ground truthed bird species observations and test performance of these algorithms on the data. I also aim to build a model that can use soundscapes to predict the occurrence of non-vocalizing species. Studies have shown that insects are the most vocalizing species in tropical habitats, however, most studies don't focus on insect vocalizations. This can be attributed to the fact that building automated models for insect species identification using acoustic data is a challenging problem. Thus, for my third objective, I will use recent developments in the field of machine learning, such as transformers, to build acoustic identification models for insects and quantify insect biodiversity.

Coastal mangrove ecosystems remain among Earth’s most valuable forests, serving as key carbon sinks and protecting billions of dollars of coastal infrastructure from sea level rise. Mangroves are also highly vulnerable to both direct human influence and growing climatic threats, with hotspots of loss scattered across the tropics. This seminar will present the groundbreaking methodology and results from a global-scale satellite-based analysis to map the drivers and extent of mangrove losses over the last several decades. Using a machine learning analysis of over one million Landsat images, we capture mangrove losses due to agriculture, urbanization, sea level rise, and extreme weather events at high resolution. This analysis is currently being integrally used to monitor global restoration and conservation initiatives, inform key mangrove preservation policies, and evaluate progress on the Sustainable Development Goals.

This seminar will also provide participants with an overview of a large-scale capacity building initiative to train thousands of students across South Asia and West Africa with cutting-edge remote sensing tools for environmental monitoring. Participants will have the opportunity to directly get involved in training and collaboration opportunities with NASA, National Geographic, Google, and Stanford University in the field of satellite-based climate analysis.

Temperatures are rising and the thermal regimes of our ecosystems are changing rapidly, becoming warmer and more variable with more frequent extreme events. The impacts of these changes are the subject of much current research on a wide variety of organisms. Important questions revolve around what determines thermal tolerance or the thermal limits of a species distribution. Are they the same thing? And how best to measure or predict them? To assess the integrated response of organisms and communities to changing thermal regimes requires systems level perspectives that draw together impacts at different scales – e.g., cell vs organ vs organism within species; or plant vs pollinator vs pathogen at community scales. I will present work collaborators and I have been doing to better understand what thermal tolerance means, what drives it, and to explore how best to assess it.

Over 80 % of the world animals have complex life-cycles with multiple life-stages.  In many of these species, each life stage experiences dramatically different selection pressures, due to living in different environments and specialising in different tasks. For example, caterpillars must avoid predation while feeding on leaves, while butterflies must fly, find mates and feed on nectar. However, all butterflies were once caterpillars, and they share the exact same genome. This raises a fundamental evolutionary question – to what extent does the resetting of the body plan at metamorphosis allow for independent adaptation at each life stage? Answering this question is essential to predict how animals might adapt to environmental change. In this talk I will describe a recent collaboration looking at the evolution of colouration across life-stages of Australian Shield bugs, as well as future research plans to investigate the evolution of thermal tolerance in Australian leaf beetles.

Tropical forests are currently undergoing large-scale structural changes, including an increase in liana abundance and biomass. As critical but frequently overlooked components of these forests, lianas can reduce tree growth and increase tree mortality, thus significantly influencing the declining pantropical carbon sink potential. Despite the increasing importance of lianas, quantitative studies on liana abundance and their impact on forest carbon stocks are almost non-existent. Recent advancements in terrestrial laser scanning (TLS) technologies have provided a new lens through which we can examine forest structures. These developments facilitate observation on an unprecedented scale and offer improved accuracy. As a result, we can now reliably measure liana structure and assess its impact on the structure and functionality of tropical forests. In this presentation, I will elaborate on how the utilization of TLS, in conjunction with other recent technological innovations in the remote sensing field, has enhanced our ability to understand lianas. Additionally, I will share the insights we have gained about the role lianas play in contributing to the already declining pantropical carbon sink potential.  

Environments shape the development of physiology but also act as potent selective sieves to shape how physiological responses evolve. I’ll briefly discuss the work my group has been doing to 1) test how early thermal and resource environments shape thermal physiology in a model lizard system (Lampropholis delicata); 2) the generality of such findings across ectotherms and 3) some new work that explores the interplay between physiological plasticity and the opportunity for selection on physiological responses in an era of climate change. 

I will describe a few recent studies in our lab in Canberra. I will describe two fish studies on Gambusia holbrooki led by PhD students. One, by Ivan Vinogradov, is soon to be published work on the link between cognitive ability and fitness. The other study, by Meng-Han Joe Chung, is partly published work that teases apart the different costs of reproduction for males. I will then describe a recently published meta-analysis by a PhD student, Lauren Harrison, testing for sex differences in variation in personality. Finally, if time permits, I will briefly describe recent theoretical work I did with Lutz Fromhage (U Jyvaskyla, Finland) on how to measure inclusive fitness.

Foraging by animals is typically understood as a way to maximise food or energy intake. However, food is a complex mixture of multiple nutrients, each having specific functional implications for animals. The dietary choices of animals in the wild are influenced by both internal (such as, sex, physiological condition) and external factors (such as, predation risk, habitat heterogeneity, seasonal influence). Such environmental stressors can inflict stress responses in animals which in turn impose higher energy demands, leading to the rapid depletion of stored carbon-rich compounds. Their depletion requires replenishment by active foraging for carbon-rich food resources and thereby imposing new nutritional demands during physiological stress.  Seasonal breeding animals have different physiological demands across their seasonal regime based on their life history traits. While the stress hormone, that is corticosterone in birds and reptiles, is essential for survival during non-breeding stages, its over expression in the breeding stage could have potential negative impacts on their reproductive activities.   Using the sexually dimorphic tropical lizard species, Psammophilus dorsalis, as our model system, we studied the differences in physiological demands across seasons and their correlation with diet nutrient composition. We quantified stress levels and energy metabolite levels from blood samples and quantified the diet of adult lizards to prey Order level and determined the C:N ratios of their whole diet across seasons. I shall present our findings from this chapter during the talk and also give an overview of related studies that were conducted as part of my PhD. 

There is a high cost of not responding to the threat of predation; therefore, organisms have evolved different risk avoidance strategies. Animals use different cues (e.g., alarm calls, kairomones, refuge density) in their surroundings to save themselves from predators. They may also use past encounter experiences to improve their antipredator responses. Such carry-over effects can benefit the same individual or subsequent generations where animals occupy the same ecological niche. In a complex life cycle, every life stage differs morphologically, physiologically and functionally. These stages occupy different ecological niches and experience different selection landscapes. In such life cycles, every life stage is separated by a tissue remodelling event. Given these evolutionary and physiological constraints, do past predator encounters carry over to the next stage and influence its behavioural response? Or do they respond according to their immediate environment?   In the first chapter of my thesis, we answered these questions using a mosquito model system Aedes aegypti. Aedes aegypti has four major stages- egg, larva, pupa, and adult. We examined the effect of predation risk experience across larval and pupal stages. Larval and pupal stages differ in morphology, physiology and function but share the same habitat and, therefore, similar threats. We manipulated the threat of predation experienced by larvae and investigated its influence on pupal behaviour. I will present my findings during the talk and an overview of my PhD work progress.