Predation is a strong selection force that can potentially change the mate-finding strategies of prey. However, what makes one prey more risk-prone to predation relative to another depends on various ecological and behavioural factors and their interactions. Predation risk can be different for different species, different sexes of the same species and even for different behaviours of the same sex. One of the questions we try to address is why we see sex-biased predation by bats on katydids (bushcrickets) and to understand that we investigated the risks associated with different sex-specific behaviours. From the wing remains of katydids collected from the roosts of a bat predator Megaderma spasma, we see interesting patterns of predation for two different katydid species. For the genus Mecopoda, more male wing remains are found in the breeding season, and more female wings are found in the non-breeding season, whereas for another katydid Onomarchus uninotatus, more female wings are found throughout the year. Interestingly, these two katydids have different strategies for mate-finding. In Mecopoda, only the males signal and the silent females move towards the singing males, whereas O. uninotatus performs a multimodal duet, where both males and females can signal and search. We conducted behavioural experiments and observed bat responses to free-moving males and females of these two katydids, while they engaged in signalling using acoustic or vibratory cues and searching by walk or flight. Flight emerged as the highest risk factor for males and females of both katydid species, whereas walking was not found to be risky.

Sleep or sleep-like behaviour has been observed in most animals examined, from invertebrates to mammals.  Sleep is ecologically important as it renders the sleeping individual vulnerable to environmental stressors, yet the evolution of sleep and its ecological context remain poorly understood. Reptilian sleep in the wild is likely to be influenced by ecological processes of predation, competition, and thermoregulation. In this talk, I present an overview of what is known of sleep ecology in reptiles. I illustrate such ecological constraints and sleep strategies (e.g. for predator-avoidance) using agamid lizards. Finally, I outline the likely relevance of sleep ecology as an evolutionary driver, its application to conservation, and other interesting research directions.

Behavioural variation is ubiquitous in the animal kingdom and typically comprises of multiple components — across-individual variation (a.k.a personality), within-individual variation, stochastic noise, and unmeasured variation. Most behavioural research tends to focus on the population mean behaviour, ignoring the aspect of inter- and intra-individual variability. Such variability has been linked to ecological, evolutionary and conservation implications with fitness consequences. Despite the recent explosion in number of studies on animal personality, the focus has been short-term, laboratory-based studies and on a limited number of personality axes.

In this study, I will study variation at the individual level along multiple personality axes, with an in-depth focus on exploratory behaviour and test how this variation links to survival, a crucial component of fitness. I will use the South Indian Rock Agama (Psammophilus dorsalis) as a model system by monitoring and assaying wild individuals throughout their lifespan. I will quantify the different levels of variation by taking repeated measures of each behavioural trait of interest and using variance partitioning statistics.

In my first chapter, I will test whether there are differences in trait variation based on the selection pressure acting on the trait - sexual selection versus viability selection. I expect that the mechanism by which the two selection pressures act would give rise to differences in how variable these traits are. Preliminary results reveal that traits under viability selection tend to exhibit higher consistent differences across individuals.

 
Taking this result forward, I will focus on a trait under predominantly viability selection - exploratory behaviour. Exploratory behaviour - a measure of response to novelty can have implications for ecology of an organism from foraging performance, habitat selection to mate acquisition and escape from predators. Further, these responses are expected to be plastic across contexts to avoid phenotype-environment mismatch. These plastic responses are expected to have correlations with behavioural types across traits and contexts.

 
In my second chapter, I will test if there is behavioural differentiation along this axis and how it varies at the intra-individual level. I will use individual responses to novel prey and novel environment as proxy for exploration behaviour and test how this response relates with foraging performance.

 
In my third chapter, I will look at behavioural plasticity of exploratory behaviour by exposing individuals to different levels of perceived predation pressures and measuring exploratory tendencies. I will also look for evidence of behavioural type-plasticity associations.

 
Behavioural variation rarely evolves and persists independent of other traits; hence it is prudent to test for fitness consequences by looking at suites of traits. In my fourth chapter, I will test for the presence of correlations between behaviours - exploration, boldness, activity, and social responsiveness (competition and dominance) and check how such a correlation, if existent, affects survival.

 
Broadly, I will look at the form and nature of inter-individual variation under different selection pressures across time and contexts and test their link to fitness. 

Organisms face the allocation problem of investing resources in different traits. Investment strategies are expected to maximise fitness by balancing the costs and benefits of investing in multiple traits used in diverse contexts, including acquiring territories, food, and mates. The trade-offs associated with trait investment are likely to be dynamic. For example, ecological factors, such as climate, temperature, and diet, and demographic factors, such as male and female densities and sex ratio, can affect trade-offs and, thereby trait investment. 

Many animals show strikingly exaggerated traits like antlers in Cervids. Such traits represent costly trade-offs because they decrease the residual resources available for allocation to other traits. Moreover, individuals within a population often exhibit variation in exaggerated traits, with relative trait sizes increasing with body size. This pattern of positive allometry where individuals ‘invest disproportionately more resources to traits as body sizes are larger’ has been proposed to be due to sexual selection. However, studies have also suggested that sexually selected traits might not universally display positive allometry; these studies provide examples of sexually selected traits that show slight negative to isometric scaling. More recent studies have proposed that whether sexually selected traits show positive allometry depends on the trait's behavioural context and functional relevance.   

A long history of examining resource investments using the approach of allometry has focused on quantifying how behaviours, morphology, and other traits scale with body size. Our understanding of the processes underlying the maintenance of positive allometry in a population is limited. Specifically, investigations of how dynamic changes in ecological and demographic factors affect positive allometry are few. Moreover, empirical studies investigating how trait allometries contribute to individual fitness are scarce. Such studies are necessary for deciphering the selective factors maintaining positive allometry in a population. 

Using the rupicolous agamid species Psammophilus dorsalis, we aim to understand how positive allometry in morphological traits is affected by dynamic variation in the selection environment. By employing microsatellite markers for genotyping and parentage analysis, we also propose to examine the contribution of positive allometry in morphological trait to reproductive fitness. Finally, in polygynous systems like P. dorsalis, males commonly use multiple traits in the competition for mates. We also aim to understand how investment patterns and relative scaling of the focal morphological traits affect the payoffs to other traits used in the competition for mates, including the diverse set of signals. The questions in the thesis will be answered using long-term morphology and demography datasets, together with behavioural observations and field experiments.

The cost-benefit framework forms the basis for current theories on the evolution of group living in animals. Much attention has been paid to drivers of intraspecific grouping in vertebrates, with recent emphasis on heterospecific groups. However, a disproportionately large fraction of vertebrate taxa choose to remain solitary at all times. Using a secondary dataset on extant species of fish, birds and mammals, the first part of this study aims to identify the suite of traits that these solitary taxa are typically associated with, and the possible benefits gained from choosing to remain solitary.

Heterospecific grouping is a widespread phenomenon because it allows animals to exploit benefits such as protection from predators or access to key resources in a manner that is more effective and energetically efficient, while simultaneously reducing the costs of competition associated with conspecific grouping.

Tropical reef fish are a system where both single- and multi-species groups are seen. The ecological significance of the latter is poorly understood when compared to other vertebrate taxa. It has been proposed that such groups might be capable of impacting the overall trophodynamics of the reef by influencing benthic invertebrate and algal community structure. Our study is aimed at understanding the different drivers that influence mixed-species grouping in reef fish. We intend on assessing factors like morphology, phenotype, resource availability and predation risk to determine their role in shaping association patterns of shoaling reef fish groups using primary and secondary data, and a combination of empirical and simulation-based approaches.

Alternative Reproductive Tactics (ARTs) refer to traits that allow individuals of a species to maximise their fitness in two or more ways. ARTs have been reported in many taxa and can manifest as discrete morphological, physiological, and behavioural differences among individuals of either sex. Various ecological contexts such as predation risk, spatial and demographic context can impact the fitness of ARTs and affect their persistence. Thus, studies on the effects of these contexts on the relative fitness of ARTS are essential, especially with respect to plastic, reversible ARTs that involve signalling. In this thesis, I will use an acoustically communicating, nocturnal species of tree cricket, Oecanthus henryi, to investigate how ecological context shapes the fitness of ARTs. Males of O. henryi can display ARTs such as calling, baffling, or acting as silent satellites to obtain copulations. Predation may affect the relative success of these ARTS by differentially affecting the mortality of males expressing these tactics. Furthermore, proximity to females may affect the relative efficacy of these tactics in attracting mates. Lastly, the interaction of demographic factors such as population density, frequency of tactic expression and sex ratio may affect the fitness outcomes of these ARTs. In this thesis, I propose to examine the effect of predation, spatial and demographic context on relative fitness benefits of different ARTs, using empirical and simulation-based approaches.

Venom is an adaptive trait that has propelled the expansion of snake lineages across diverse habitats. Natural selection optimises the potency, composition, and lineage-specificity of the snake venom arsenal for effective prey capture or deterrence of predators. Venoms of several closely related snake species that inflict life-threatening bites in humans have been documented to exhibit tremendous spatial and temporal venom variation. However, venom research in India has predominantly focussed on assessing the compositional variation among captive snake populations from restricted locales. Several questions pertaining to the evolutionary ecology of snake venoms remain unanswered. Therefore, studies integrating the knowledge on natural history and trophic interactions of medically important Indian snakes is warranted. 

As part of my PhD research, I propose to decipher the role of various ecological and environmental determinants on the diversification of Indian snake venoms. To understand the influence of the environment, I will sample snake venoms from the major biogeographic zones across the country. A multi-faceted approach involving proteomics, biochemical analysis, pharmacological assessment, and toxicity studies will be employed. Further, I will evaluate the role of ecological traits, such as ontogeny and gender, in shaping venoms by housing venomous snakes under captivity. The differences in their venom activities and toxic potencies will be evaluated. Moreover, as the feeding ecology of snakes plays a significant role in determining venom characteristics, the prey-specificity of these venoms will be determined using in vitro and in vivo experiments. Briefly, the kinetics of interaction between venom toxins and their target receptors (synthetic mimotopes) sequenced from various natural prey animals will be evaluated using bio-layer interferometry.  In vivo experiments will involve toxicity assays against diverse model systems including arthropods, amphibians, reptiles, birds, and mammals. These experiments will also shed light on the evolution of venom resistance in target organisms. Finally, the repercussions of venom variation at various levels on the snakebite treatment in India will be investigated by performing WHO-recommended preclinical assays. These studies will decipher the effectiveness of the currently employed conventional antivenom therapy in mitigating snakebite mortalities and morbidities across the country.

Microbial communities are highly dimensional, with many species and many variable environmental factors. Macroecology, which studies communities as statistical ensembles, is a promising way to connect these complex data to mechanistic models. In this talk, I will discuss a minimal set of macroecological patterns that characterize the statistical properties of species abundance fluctuations across communities and over time. A mathematical model based on environmental stochasticity quantitatively predicts these three macroecological laws, as well as non-stationary properties of community dynamics. Building on these results, it is possible to disentangle the (statistical) properties that determine ecosystems' stability over time and reproducibility across communities.