Venom, being an adaptive trait, has propelled the expansion of snake lineages across diverse habitats, such as the biogeographically distinct Indian landscapes. Natural selection optimises the potency, composition and lineage-specificity of the snake venom arsenal for effective prey capture or predator deterrence. Therefore, venoms of several closely related snake species have been documented to exhibit tremendous spatial venom variation owing to their distinct evolutionary ecology. However, research on venoms in India has predominantly focused on assessing the compositional variation in certain snake species from restricted locales. These studies have also evaluated the venom variation only from a biochemical perspective without considering the ecological and evolutionary significance of such compositional differences. Hence, several questions pertaining to the evolutionary ecology of Indian snake venoms remain unanswered.

Naja naja and Daboia russelii are two medically important snake species that are widely distributed across distinct bioclimatic regions of India, including arid deserts, fertile plains, rainforests and hot-humid coasts. In addition to their clinical relevance in the snakebite scenario, these two species are fascinating model systems to understand the relationship between evolutionary ecology and venom variation. This doctoral thesis was designed to decipher the relationship between various ecological and environmental determinants and the variability in N. naja and D. russelii venoms. For this, venoms of wild-caught snakes from the major biogeographic zones across the country were sampled. A multi-faceted approach involving proteomics, biochemical analysis, pharmacological assessment and toxicity studies was employed to characterise the extent of variability. These studies revealed remarkable intraspecific variation across populations of these two species. The venoms varied significantly in terms of their composition, functional profiles and toxic potencies.

Further, the contribution of various abiotic, biotic and life history factors in dictating this variation was evaluated. A theoretical prediction model was developed to explain the variation observed in the enzymatic activities of D. russelii venom due to the combined effect of bioclimatic variables in a region. The feeding ecology is amongst the major biotic factors that drive venom evolution. Therefore, the prey-specificity of N. naja and D. russelii venoms was examined as a proxy to understand the relationship between compositional variation and diet. The venom specificity was determined through in vitro binding and in vivo lethality experiments against distinct prey organisms.

In addition to interpopulation variation, venoms were documented to vary between individuals within the same population. Therefore, the extent of intersexual and ontogenetic venom variation within a population was characterised by housing multiple clutches of these venomous snakes under captivity. The differences and similarities in the venom composition, potency and specificity across sexes and ontogenetic stages of N. naja and D. russelii individuals were recorded. While intersexual variation was not observed in either of the species, marked differences were observed between the venoms of young and adult D. russelii snakes. However, adult and juvenile stages of N. naja were found to produce functionally similar venoms. These results shed light on the influence of distinct ecologies on temporal venom variation across the developmental stages of a species.

Finally, the repercussions of venom variation at various levels on snakebite treatment in India were investigated by performing WHO-recommended preclinical studies. These studies highlighted the shortcomings of the currently employed conventional antivenom therapy in mitigating snakebites across the country. Overall, these studies also provided valuable insights for the development of advanced snakebite therapeutics that have the potential to save the lives, limbs, and livelihood of India’s thousands of annual snakebite victims.

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In nature, a single selection pressure can act on multiple traits of an individual animal, and a single trait of an animal can also be under multiple selection pressures. Given the potential for complex trade-offs acting across multiple traits, it would be more ecologically relevant and meaningful to study multiple traits of an animal in the wild, where they are simultaneously under multiple selection pressures. However, such processes have rarely been examined in animals, especially in their natural habitat. In my thesis, I will examine how risky behavioural traits are expressed under multiple selection pressures and how variation in the expression of multiple risky behavioural traits contributes to an animal’s fitness. I will also examine the correlations between different risky behaviours and test hypotheses for such correlations. I will conduct behavioural experiments on Psammophilus dorsalis in their natural habitat to answer these questions. In my 1st chapter, I will examine how natural and sexual selection factors simultaneously affect decision-making in response to threat in adult male P. dorsalis. In my 2nd chapter, I will examine correlations between multiple risky behavioural traits and their relative effects on fitness in adult male P. dorsalis. In my 3rd chapter, I will examine if the expression of risky behavioural traits is heritable in adult male P. dorsalis.

Arid grasslands are open natural ecosystems covering 19% of Earth’s terrestrial surface. They are grazed by both wild animals and livestock. Grazing based livestock farming is the basis of rural Economy in India, especially in arid regions where agriculture is not economical. However, increasing livestock poses pressure on continuously declining grasslands decreasing native flora and fauna. Hence, my study is focused on the difference in plant community composition, plant diversity, plant traits, and soil nutrients in grazed and long-term ungrazed sites in Chitradurga, Karnataka. I hypothesize that plant diversity and soil C:N ratio will be lower in grazed sites. Plant community composition will differ between the two sites with different plant traits (taller, higher leaf area, higher leaf dry weight in ungrazed). Preliminary results show that plant richness is higher in grazed sites with no significant difference in diversity between the two conditions. Plant species composition in grazed sites were more similar than in the two ungrazed sites. I also found that some plant species differed morphologically between grazed and ungrazed sites. To unravel whether this difference was plasticity or due to evolution, and if it is adaptive, I will carry out common garden experiments followed by reciprocal transplantations. In unfavorable conditions some plants might exist only as seeds. To get a picture of the potential vegetation of the grazed and ungrazed sites, I will compare the plant composition in the soil seed banks, between the long term ungrazed and grazed sites. Because grazers are eating away plants before the reproductive period, I hypothesize that soil seed bank diversity will be lower in grazed than ungrazed sites. Finally, I will conduct a manipulative study, on the short-term effects of grazing on plant communities using grazing exclosures, or a controlled study of plant decomposition rate. Overall, this study will increase our understanding of grassland and grazing ecology in an arid system, while providing a primary database of herbaceous communities in these landscapes. It will provide knowledge about the recovery timing of degraded grazed lands under arid conditions, which is useful to policy makers and conservation biologists planning restoration and conservation programs.

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TBD

In this talk, I will give a broad-brush overview of three areas in the field of animal coloration in which I think we have much to learn and discover – and the current efforts of my group to tackle a small part of them. The first area is the function and perception of iridescent and shiny colours that change appearance as signallers or receivers move. The second area is the intersection between light and heat – optical properties beyond the limits of human and animal vision and their consequences for thermal control. The third area is new ways to produce colour through pigment-structure interactions. These areas hold great promise for both fundamental biological understanding and bioinspired applications.

The golden langur is one of the most range restricted colobine monkey, confined to the region between Sunkosh and Manas rivers in Bhutan and adjoining Assam (India). It is closely related to the widely distributed capped langur which is distributed from Eastern Bhutan, Northeast India, parts of Northern Bangladesh to Southern China, and Northwestern Myanmar. Golden langur has been divided into two subspecies whereas capped langurs into four. However, the subspecies status of golden langur is still being debated. Previous studies have hypothesized that an isolated population of capped langurs might have speciated into golden langurs due to geographical barriers like rivers and mountains. This would represent a classic case of budding speciation; wherein peripheral isolates of widely distributed species evolve into a distinct lineage. Furthermore, the presence of intermediate forms between golden langurs and capped langurs found in an overlap zone in central Bhutan hints at a possible hybridization between these two species. Alternately, these intermediate forms might represent clinal variation between golden and capped langurs (intergradation). Given this background, for my thesis research, I aim to investigate the origin and evolutionary history of golden langurs vis-a-vis capped langurs by using multiple nuclear and mitochondrial markers. Genetic data will be used to address three specific questions. 1) Does genetic data support splitting of golden langur into two subspecies? 2) Is there genetic evidence for budding speciation? 3) Are the intermediate forms a case of hybridization or does it represent intergradation?

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.