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. 

India is considered the world's snakebite capital, where over 58,000 snakebite fatalities are registered annually. Most bites are primarily attributed to four snake species: the spectacled cobra (Naja naja), common krait (Bungarus caeruleus), Russell's viper (Daboia russelii), and saw-scaled viper (Echis carinatus) that are collectively termed as the 'big four'. Recent research has unravelled a significant variation in snake venom composition and toxicity at inter- and intraspecific levels, resulting in an alarming ineffectiveness of antivenoms - the only available treatment for snakebites. However, the extent of venom variability, which often results from differing ecologies, evolutionary histories, and/or environmental conditions, remains largely uninvestigated in the majority of clinically important snakes. For example, the influence of varying ecology and environment on the venom of the common krait (B. caeruleus), the snake species with a near-pan-India distribution responsible for the second-highest number of snakebite-related deaths in India, has not been investigated to date. To address this knowledge gap, my PhD research focused on assessing the biogeographic venom variation in this species across India. Furthermore, I have evaluated the repercussion of this geographic venom variation on the preclinical efficacy of commercially available Indian antivenoms. Similarly, the extent of intrapopulation venom variation, especially at finer geographic scales, remains poorly understood. I had, therefore, employed an interdisciplinary approach involving venom proteomics, biochemistry, and pharmacology, to assess venom variation in monocled cobra (N. kaouthia) sampled across a small spatial scale ( <50 km). Finally, I have evaluated in vitro and in vivo venom binding and neutralisation capabilities of conventional antivenoms in countering toxicities inflicted by various individuals in this population. While conventional antivenoms have saved thousands of lives, they suffer from numerous flaws, such as ineffectiveness against necrotic effects, reduced dose-effectiveness that often leads to many secondary reactions, including fatal anaphylaxis, and unavailability in many primary health centres. Secondary metabolites of plants have been shown to effectively neutralise snakebite pathologies, especially the local effects such as haemorrhage and necrosis. Therefore, I have assessed the antivenomic potential of medicinal plants, such as avaram (Cassia auriculata), utilised in traditional medicine. The neutralising potency of Cassia auriculata flower extracts against medically important snake venoms has been evaluated using in vitro experiments. Finally, I identify the active components in these plant extracts and will explore their potential role in treating snakebites in India.

Mutualisms are potentially conflict laden interactions, vulnerable to collapse. How mutualisms are stabilized against collapse is a long-standing question in the field. A commonly accepted explanation is that provided by the extension of biological market theory and of host sanctions— one of the partners (symbionts) provides options of commodities or services of varied quality and the other partner (host) chooses from among the symbionts, by selectively allocating resources to more cooperative partners. This explanation brings forth the importance of considering resource allocation, since mutualisms are basically consumer–resource interactions. However, it is one-sided, focussing only on the control on allocation that the host manifests. It ignores any control exercised by the other partner in accessing the resources. These partners have tools for accessing the resources from the host, which can be utilized for controlling the quantity of resources obtained, especially in interactions involving plants, where a source–sink relationship can be established. Sinks are well known manipulators of allocation patterns. Hence a comprehensive study of resource allocation structure and control within mutualisms from the perspective of both hosts and symbionts is a necessary step in understanding stability of mutualistic interactions. Interaction between figs and their pollinator wasps provides us with a good model system to study resource allocation patterns and strategies. The interaction takes place in a closed inflorescence called fig syconium, within which fig seeds and pollinator offspring develop. It provides us with an opportunity to manipulate the occupants of syconium to study the effects on resource allocation. 

In the first part we try to understand patterns of allocation within a fig syconium with reference to biomass and stoichiometry of components of the fig syconium. We show that most of the resources allocated to a syconium are spent on making the syconial wall and the number of pollinator galls has a significant positive effect on the mass of the wall. We also find that pollinator wasps require more resources to develop compared to seeds. When limiting nutrients are involved, asymmetry in nutritional requirements can potentially determine the number of pollinator wasps that a tree can support. Next, we tried to understand, if and how the type and density of occupants influence resource allocation to a syconium. We show that more resources are allocated to syconia that contain both seeds and galls compared to those containing just one of them. This indicates that there might be interaction between the occupants to maximize local resource allocation, showing some level of interdependence between the partners. The size of the syconium increased with increasing density of occupants. However, at low density of occupants, presence of seeds increased the biomass allocation, whereas at high density, presence of galls increased allocation to the fig syconium. Our results thus show that resource allocation in pollination mutualisms is dynamic, and, regulated by both the interacting partners depending on the context of density of occupants.  

We also investigated the role of growth hormones in the differential resource demand exerted by the occupants of the syconium, i.e. seeds and pollinator galls. A preliminary analysis has indicated higher amount of growth hormones released by the pollinator galls. Any study on resource allocation would be incomplete without information on carbon exchange. We determined carbon dioxide exchange of whole syconium to understand if fig syconia can meet some part of their resource demands by photosynthesis. Measurements of respiration rates of syconial occupants has indicated that pollinator galls have higher respiration rates compared to seeds. Overall, pollinator galls are more resource expensive when compared to seeds and can also result in production of larger syconia. Our results highlight the importance of studying resource allocation from the perspective of both the partners.

Southeast Asia, Sundaland, and Australasia are some of the most sought-after biogeographical regions within which to test hypotheses pertaining to dispersal and diversification. While cyclic fluctuations in sea levels, and the land bridges that were periodically exposed and submerged as a consequence, have been invoked to explain the accumulation of biodiversity in the region, recent geological studies have shown that most of the region remained aerially exposed until as recently as 500 KYA. This implies that contrary to historical belief, alternate processes may have driven the dispersal and diversification of terrestrial and semi-aquatic organisms in SE Asia, the Sunda plate, and Australia. In this collaborative paper, Bernstein, de Souza, et al. examine these ‘alternate processes’, specifically the influence of major shifts in river systems around 17 MYA, as drivers for diversification and dispersal in the widespread, yet poorly studied ‘OrientalAustralian Mud Snakes’ (Serpentes: Homalopsidae). These snakes, given their predominantly semi-aquatic habit, form an ideal model system to study biogeographic processes, given that they have the rare advantage of the availability of both terrestrial and aquatic dispersal routes. In our paper, we use a target capture genomic approach to resolve the phylogeny of this hitherto understudied group, identify their biogeographic origins, and highlight the impacts of paleoclimate (sea-level fluctuations vs. riverine connectivity) on their present-day ranges and abundances. We use recently developed methodology for the extraction of DNA from formalin-preserved museum tissue to present the most complete phylogeny of homalopsids to date (species/genera coverage of 81% and 90% respectively, up from 45%/45%). Our phylogenomic and divergence time dating elucidate that these snakes are much younger than previously thought (~27.7 MYA vs ~45.3 MYA) with the origin of the crown group occurring in the Oligocene. I further incorporate Ancestral Trait Reconstructions (ATRs) which form a portion of my PhD’s Chapter 1, to elucidate that the most recent common ancestor of this clade was a terrestrial serpent (vs. prior assumption that it was aquatic). While our data were neither able to resolve the ancestral range of the crown homalopsid, nor was it able to conclusively comment on the drivers for homalopsid diversification, our divergence dating in tandem with the ATR analyses was able to identify Indochina was the cradle for all aquatic homalopsids. This implies that the single switch from terrestrial to aquatic habit in ancient homalopsids, in combination with riverine connectivity has resulted in the surprisingly high diversity of aquatic homalopsids vs. their terrestrial extant counterparts. In this presentation, I also touch upon my ongoing research towards my Chapter 2 (phylogeographic comparisons between brackish water-tolerant homalopsids and freshwater-restricted natricids) and Chapter 3 (species distribution models predicting current and future habitat suitability for semiaquatic snakes within the Indian biogeographical region) chapters.

Colors in organisms can be produced either chemically by pigments or physically by the interference of light scattered from biophotonic nanostructures or sometimes in combination. Fade-proof, vivid, saturated structural colors that have evolved over millions of years of optimization are an ideal source to look for natural solutions to our current technological challenges in optics, sensing, etc. and can provide facile biomimetic routes for eco-friendly materials synthesis for functional applications. However, given that the underlying nanostructures are overwhelmingly diverse in form and function, their characterization has lagged for over a century. I have pioneered the use of synchrotron Small Angle X-ray Scattering as a high throughput technique to structurally and optically characterize biophotonic nanostructures from hundreds of species, in a comparative framework. This has led to the understanding that all these diverse, mesoscale nanostructures share a unifying theme – they appear to be self-assembled within cells by bottom-up and directed processes.  I led the discovery of the first biological single gyroid photonic crystals in the iridescent green wing scales of certain butterflies that beautifully pre-empt our current engineering approaches and recently, within some bird feathers. The latter appears to be the first directly self-assembled single gyroid known to science and at the hard to achieve optical length scales. In this talk, I will broadly summarize our current state of knowledge about the structure, function, development and evolution of organismal structural colors in birds and insects, as well as discuss some future directions on how understanding the intracellular development of biophotonic nanostructures can lead to novel, eco-friendly routes to mesoscale synthesis for advanced applications from sensors, photonics, energy harvesting to catalysis.

Animal groups across taxa -- from insects and birds to fish and mammals -- exhibit a high degree of synchrony in their movement. Various empirical, computational and theoretical studies over the past two decades focus on how simple mechanisms produce these large-scale fascinating patterns. While a large number of empirical and theoretical studies examine the so-called proximate aspects of collective motion, only a few of them have investigated the functional or evolutionary significance. An important hypothesis for the function of group-living is that of reduced risks of predation. We hypothesise that not just group living but synchrony of group movement facilitates reduced risk of predation. For my PhD thesis, we will study this using theory and computational models in close collaboration with empirical work. We will employ empirically motivated computational spatial explicit models to study how anti-predatory behaviours at the level of individuals -- and crucially, flocking interactions among individuals -- result in collective escape dynamics of flocks. We will compute the effectiveness of information transfer via metrics such as spatial and temporal correlation measures or transfer entropy-based measures. We will compare how the efficiency of information transfer depends on the type of flocking interactions -- for example, when agents only interact stochastically with one of the near neighbours (as suggested by recent empirical studies) versus interaction with multiple neighbours (as suggested in classic physics-inspired modelling studies). These findings will later be compared with the results of empirical studies led by my colleagues in the lab to examine if the type of interaction (with just one neighbour or multiple neighbours) changes during collective escape dynamics. In summary, through this thesis, we will shed light on the functional importance of collective motion and the evolution of collective movement in both predators and prey. Through these models and empirical studies, we will gain insights on information transfer among collectively moving organisms, a topic with relevance in many ecological scenarios, ranging from foraging, predation to even human crowds.