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.

Biologists trying to understand extinct animals typically use rare clues to form tentative inferences. Reconstructing the past is always challenging but analyzing the structure and composition of features that grow continuously sometimes yields evidence of life conditions in chemical and isotopic traces. In this way, we can retrieve records of maturation and behavior archived in mineralized layers of tusks of mastodons (elephant relatives), allowing us to follow a single individual for years, across entire landscapes. For the first time, we identify seasonal migratory behavior that may have been key to meeting the challenges of reproduction near the end of the last Ice Age. We reveal here the story of one mastodon’s struggles and victories, from adolescence to the mating-season battle that ultimately claimed his life.

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.

Population biology is built on a strong mathematical foundation developed during the Modern Synthesis and encapsulated by the fields of theoretical population genetics, evolutionary game theory, and quantitative genetics. Historically, these formalisms have often worked with infinite populations, ignoring the effects of demographic stochasticity. Finite population models in population genetics usually assume a fixed population size and are of limited applicability in the real world, where population sizes routinely fluctuate. In this talk, I will outline how ideas from statistical physics can be used to analytically describe evolving populations from biological first principles. Starting from a density-dependent ‘birth-death process’ describing an arbitrary closed population of individuals with discrete traits, I derive a set of stochastic differential equations (SDEs) for how trait frequencies change over time. Along with recovering the effects of the standard evolutionary forces of selection, mutation, and drift, these SDEs also reveal a new directional evolutionary force, ‘noise-induced selection’, that is particular to finite populations and has been largely overlooked in standard mathematical formulations of evolution. Noise-induced selection can reverse the direction of evolution predicted by infinite-population frameworks, with implications for simulation studies and real world populations. Our equations also recover well-known results such as the replicator-mutator equation and Fisher’s fundamental theorem in the infinite population limit. I will try to stick to intuitive arguments and keep formal mathematics to a bare minimum in the talk.

Snakes are among the most notable reptilian lineages ubiquitous in several ecosystems across the globe. The innovation of the venom system has strongly underpinned their evolutionary success. Snake venoms are complex cocktails of toxins that collectively facilitate many ecological functions such as predation, defence, conspecific competition, or a combination thereof. Many of these venomous snakes can potentially inflict medically significant envenomation in humans. In India, the Indian spectacled cobra (Naja naja) is one of the “big four” medically relevant snake species that are responsible for most human envenomation and lethality. With a near-country-wide distribution, N. naja is a generalist snake that inhabits diverse ecological habitats. Geographically disparate populations of this species show observable differences in various phenotypic traits, including colouration, scalation, and hood markings, as well as in their venom composition. While the genus has garnered global taxonomic and venom research attention, detailed studies investigating molecular phylogenetics, the population genetic structures, and their influence on venom composition and potency are lacking for the Indian congener, N. naja. Taxonomic re-evaluations have led to the decomplexation of the N. naja complex into different Asiatic species of Naja. The nomen, ‘N. naja’, is retained for the populations present in the Indian subcontinent, with India Orientalis as its type locality. Based on morphological considerations, Deraniyagala (1960) proposed five subspecies of N. naja, which were subsequently rejected by researchers, clubbing them all as a monophyletic group. This synonymization, however, was without molecular evidence. The spatially disparate populations can also be structured into phylogenetic units corresponding to geographical regions and be closely associated with contemporary and historical population dynamics. Understanding the evolutionary relationships of these populations within a phylogenetic framework and assessing the genetic diversity would widen the understanding of the systematics of this medically important group. Even though the phylogenetic pattern by itself is not a good predictor for venom composition, phylogenetic studies can shed light on the underlying patterns of the evolution of the venom of the species. For my PhD, I aim to leverage an integrative approach involving phylogenetics, phylogeography, and population genetics to understand the evolution of N. naja across its range of distribution and the possible geological events responsible for its current distribution. Furthermore, the project will also evaluate the extent of gene flow between the populations and investigate the role of biogeographic conditions and population genetics on the venom composition and, consequently, venom potencies.

Forty years after the discovery of HIV as the causal agent of AIDS there is still no vaccine. Yet the COVID19 vaccine was designed and developed in less than 3 months. This scientific success has been largely recognized as a direct product of 25+ years investment in HIV research. Indeed, while the enormous antigenic diversity of HIV remains a major challenge, technological innovations in antibody discovery and development platforms allowed the discovery of a new generation of potent and broad neutralizing antibodies (bnAbs) which are not only being evaluated as prevention products but also used as template for vaccine design. The first approaches led to re-evaluation of partnership models to make antibody-based treatment more affordable and accessible. The second led to the development of novel vaccine concepts which successful evaluation in proof-of-concept Experimental Medicine Trials renewed hope that an HIV vaccine is achievable. Together with the establishment of global scientific and clinical capacities, these advances offer new opportunities way beyond HIV to address other Global Health challenges.