Animals across multiple taxa form groups for various benefits. These groups can be formed with members of the same species or different species. When members of different species of birds forage and move together, they are called mixed species bird flocks (hereafter, MSFs). MSFs provide enhanced benefits such as reduced predation risk and increased foraging efficiency but also impose costs. This cost–benefit trade-off affects flock composition as species join when benefits outweigh the potential cost of associating. Benefits gained by joining a flock will vary among species, which is likely to be context-dependent. Therefore, my thesis aims to understand MSF compositions across different contexts such as (a) elevational gradients, (b) biogeographic regions and (c) phenotypic traits.

Microclimates (temperature and humidity) along with prey abundance and diversity are expected to change with increasing elevation, making conditions harsher, which influence MSF interactions. Therefore, in Chapter 1, I plan to investigate variation in MSF composition and networks along with microclimates and prey availability across an elevational gradient (1500 m to 3200 m ASL) in Kedarnath Wildlife Sanctuary, Uttarakhand, in the Western Himalaya.

      MSFs represent a subset of the avifauna in most forested regions. Studies on composition of MSFs across biogeography hold potential to better understand species roles and community organization. Therefore, in Chapter 2, I plan to compare the species composition of flock types across forest strata in three biogeographic regions (Eastern Himalayas, Western Himalayas and Western Ghats) and examine species roles based on taxonomy, body size and behaviour.

      Species traits play a major role in flock composition to minimise costs and maximise benefits (by being similar in certain traits and dissimilar in others). Therefore, in Chapter 3, I plan to conduct a global analysis to answer the question. “Do birds of a colour flock together?”. I will use null models to compare observed flocks at 24 sites globally with random flocks to investigate whether birds in MSFs are more similar in colour than expected by chance.

Overall, my thesis will explore the factors that drive species participation and association in MSFs.

Human activities have already modified over 75% of the world's land ecosystems. Ecosystems continue to be transformed into agricultural farms and cities, reducing natural habitats and increasing wildlife activity in human-dominated areas. In India, agroecosystems are known to support many carnivores. While these carnivores utilise agroecosystems as pathways and as sites for foraging and denning, anthropogenic structures may act as edges or barriers that restrict and alter the movement of the animals and even cause behavioural avoidance of specific regions. Additionally, anthropogenic environments could be stressful, resulting in a physiological cost that could lead to health problems. Wild animals must demonstrate flexibility and adaptability in their behavioural and physiological strategies to navigate and survive in an anthropogenically-altered environment. Furthermore, domesticated animals also use the agroecosystem matrix and interact with the wild animals in these areas. A key example is the high density of free-ranging dogs in human-dominated landscapes that now form a potential prey base for large carnivores. The predation of village dogs can also serve as a direct catalyst for conflict between humans and wild carnivores. Therefore, this study aims to examine the challenges and strategies wild and domestic carnivores face in agroecosystems by examining movement behaviours and physiological and cognitive responses. The first aspect on wild carnivores will focus on jackals (Canis aureus indicus), jungle cats (Felis chaus) and Indian foxes (Vulpes bengalensis) ranging across the rural and peri-urban areas of Baramati, Daund, and Indapur sub-divisions (Talukas) of Pune District, Maharashtra in West-Central India. We will determine the movement strategies of these mesocarnivores in response to anthropogenically created edges using telemetry data. We will also assess stress levels (measured as glucocorticoids from fur) and problem-solving abilities (using a novel puzzle box experiment) of the mesocarnivores that live in areas that vary in their proximity to human-dominated landscapes. For the effect of wild carnivores on domestic carnivores, we will investigate the effects of leopard predation on free-ranging dogs by comparing the population and behavioural variations of dogs in Nashik and Pune that are spread across a unique gradient, ranging from no-leopard regions, areas with recent leopard presence and long-term leopard areas. The comparative approach provides a novel opportunity to understand the concept of the landscape of fear in a human-dependent species in human-dominated landscapes. Furthermore, it could help us deepen the understanding of both the positive and negative impacts of free-ranging dogs within the human dimensions of dog-wildlife interactions in these landscapes.

Interspecific interactions are an important part of species’ life histories and play a role in maintaining ecosystem function. One of the most striking examples of networks of multi-species interactions is exemplified by mixed species flocks (hereby MSFs). MSFs are groups of birds belonging to two or more species that forage and move together. MSF participants benefit from easier access to food resources and predator avoidance, which in turn influences the fitness of participant individuals. Network theory helps elucidate how these associations might change because of environmental and anthropogenic factors. Climate change and habitat degradation by humans pose serious threats to biodiversity, causing range shifts, local extinctions and the disruption of biotic association networks. These changes are much more noticeable across large gradients within a relatively shorter period of time. I plan to study how the network properties of MSFs change along the elevation gradient in Eaglenest Wildlife Sanctuary, Arunachal Pradesh. Additionally, I try to understand the mechanism of changing properties by testing the widely proposed Open Membership Hypothesis. The northern and southern aspects of the Himalayas show a remarkable difference in their habitat, the northern aspect being warmer and drier. Furthermore, in our study area, the southern aspect is relatively undisturbed, whereas the north is more anthropogenically affected. Range shifts among species have begun to occur at different rates across these two aspects, leading to novel interactions on the northern aspect, but not on the southern. I will compare the MSF networks occurring in the two habitat types on either slope of the mountain in the eastern Himalayas and explore if the roles of species change within networks across climate and anthropogenic gradients.

The Indian subcontinent has a unique geological history. Its unique history in conjunction with the topological and climatic heterogeneity has resulted in incredible biotic diversity. In this talk, I focus on lizards of the family Scincidae (commonly known as skinks) as a model system and provide a synthesis of studies that unravel their biogeographic patterns in the Indian subcontinent. As a part of this synthesis, I also highlight some of the studies from my lab at NISER Bhubaneswar (https://biogeosys.in/) that have contributed to our understanding of Indian skink biogeography.

Venom is a complex cocktail of biologically active proteins, salts, and organic molecules. The venom toxin-coding genes in animals have convergently originated from endophysiological protein-coding genes via gene duplication, followed by accelerated evolution. Venom research has primarily focussed on snake venoms because of their remarkable compositional variation and the negative impact of snakebites on human health. Research has highlighted that conventional antivenom, the mainstay treatment for snakebites, is ineffective in countering the inter and intraspecific variations in snake venoms. Therefore, in the first chapter of my thesis, I will employ our understanding of venom evolution to design a broadly effective snakebite therapy. With the help of comparative venom gland transcriptomics and evolutionary analysis, I will identify regions in the major venom toxins that remain conserved across populations, regions and even species. I will then synthesise sequences coding these epitopes and undertake DNA immunisation of small mammals (e.g., mice and rabbits). I will employ advanced technologies in antibody discovery, including B cell sorting and yeast display selection, to discover and recombinantly express neutralising antibodies. By targeting such conserved epitopes in the major venom toxins, particularly the three-finger toxins (3FTx) and snake venom metalloproteases (SVMP) from multiple species of elapid and viperid snakes, I aspire to achieve a broad breadth of neutralisation against the most medically important snakes of the Indian subcontinent.

In addition to the evolutionary design of antibodies, I will explore the potential use of animal immunisation with specific toxin families in discovering broadly neutralising antibodies (bNAbs). In Chapter II, I will attempt to discover bNAbs from large mammals immunised with the major venom toxin families from snakes in India and sub-Saharan Africa. Since the immune systems of these animals only get exposed to the major snake venom toxins, it greatly enhances our chance of discovering bNAbs against snakes across continents.

In addition to claiming the lives of over 58,000 Indians annually, snakebites result in over a hundred thousand immutable injuries each year. Research demonstrates that conventional antivenoms are ineffective in countering the morbid effects of snake envenoming. Unfortunately, very limited research has been undertaken towards solving this socioeconomic problem. Therefore, in the third chapter of my thesis, I will undertake an antibody discovery campaign to discover and recombinantly express neutralising antibodies against toxins that inflict morbid symptoms. I will exploit the unique properties of the camelid single heavy chain antibodies (VHH), which offer several advantages over mammalian immunoglobulins, including smaller size, greater tissue penetration potential, and thermostability. As these VHH antibodies are easy to manipulate and humanise, they will greatly reduce the adverse effects of snakebite treatment. 

Overall, with the broadly neutralising antibodies discovered against 3FTx and SVMPs - the two major toxin families in India’s medically most important snakes - I hope to save the lives, limbs and livelihoods of India’s 100,000 annual snakebite victims. In addition to advancing snakebite therapeutics, the findings of my thesis will shed light on the evolution of this highly adaptive complex cocktail.

Inter-sexual selection, or mate choice results in the evolution of expensive and conspicuous traits in many systems. The use of such traits in attracting mates is called sexual signalling. Sexual signalling has largely been studied in the context of indirect competition among males and mate choice by females. Historically, sexual signalling in females was expected to be of limited consequence. However, there is growing evidence of sexual signalling in females that involve energetically costly investments and elaborate conspicuous traits. Do females modulate the use of sexual signals to maximize benefits and minimize costs?

Given the limited understanding of sexual signalling by females in polygynous mating system, we first examined the repertoire of sexual signalling exhibited by females of the Peninsular rock agama Psammophilus dorsalis. We further investigated how females strategically use their sexual signals in response to important factors that may affect the benefits of signalling. In socially polygynous mating systems, males typically invest in elaborate ability-based or honest displays which are intended towards female receivers. Although strategic signalling in males has received greater research attention, here too key questions of how competitors may affect their signalling is poorly understood. Sexual signalling males typically experience male competitors in their environment. We lack a comprehensive understanding of the impact that such unintended audiences have on male sexual signals. We studied how strategies of male signalling are shaped by both mate and competitor environments.

To understand the repertoire of sexual signalling, we set up a context for females to display by simulating the presence of a breeding male by presenting artificial male models to individually tagged female lizards. We found that females use a range of behaviours including stereotypical body postures and dynamic colour signals. We compared the response of lizards to cues of intra-sexual competition and found that distinct signals were used in the contexts of mate attraction and intra-sexual competition.

To understand how females strategically use their sexual signals, we evaluated key hypotheses for how females should modulate their signalling, including male quality, access to high quality mates and breeding season. We simulate male quality using artificial male models to individually tagged, and intensely monitored wild female lizards. We found that females invest

more in signalling towards high quality males and increased their investment towards the later part of their only breeding season. Contrary to that which is typically expected in a polygynous mating system, females not only invest in costly and elaborate sexual signals, but they also modulate their usage to maximise their benefits and minimise their costs. We argue that, even in polygynous mating systems, dispersed distribution of individuals can result in females experiencing limitation in mate availability, resulting in costly sexual signalling.

To understand how males strategically use signals in response to a combination of competitor and mate environments, we collected information on where lizards were found relative to other conspecific lizards. Since Peninsular rock agama change colour states, we then identified how individuals strategically modulate the use of colour signals with respect to other lizards present in their vicinity. We measured the relative size of male neighbours as size can be a measure of competitive ability in contest competitions. We find that individuals appear to modulate the use of sexual signalling in response to both males and females in the vicinity. We found that displays increased with increase in the potential number of mates, and decreased with competing male effect. We found that relative size affects their response to competitor abundance, with smaller males reducing the use of sexual signals in competitor environments.

My thesis highlights the wide repertoire of sexual signals seen in females of a socially polygynous species of lizard and the strategic use of sexual signalling in both males and females. Females exhibit sexual signalling with well-defined sexual signalling postures and colour-based displays that are different from other social contexts. Females, not only use their signals in specific contexts but also use them where they gain maximum benefits. The study emphasizes the scarcity of high-quality males that females may encounter, even in species adhering to conventional sex roles. We demonstrate how female invest in sexual signalling in response to both quality of mates as well as the time of breeding season. We highlight how males flexibly modulate the use of sexual signals through their colour trait in a dynamic environment with breeding females and competing males. My thesis challenges the conventional sex roles in sexual signalling while also investigating the nuanced mating strategies of males and females in a polygynous lizard.

Alternative reproductive tactics (ARTs) are discrete phenotypes employed by individuals of either sex within a species to maximize their reproductive success in varying social and environmental conditions. These tactics often involve different ways of competing for mates or different tactics for parental investment. Conditional ARTs are a class of ARTs where individuals express an ART depending on an extrinsic or intrinsic cue. The fitness of conditionally expressed ARTs may not necessarily be equal for their persistence. However, there exists a class of conditional ARTs called reversible or flexible ARTs wherein individuals reversibly switch between ARTs in response to a cue. In systems which show flexible ARTs, selection could favour genotypes that gives rse to ARTs that have similar fitness. By virtue of the similarity in mating benefits amongst ARTs, individuals can seamlessly switch between ARTs depending on cues without necessarily incurring fitness losses. My thesis attempts to evaluate the mating benefits as a fitness component of flexible ARTs in Oecanthus henryi. Oecanthus henryi is a tree cricket found in the scrublands of the Indian sub-continent. O. henryi males flexibly adopt three different ARTs to obtain mates. Males can either call to attract females or remain silent. Males can adopt a third tactic, called baffling, wherein males call through a hole they make near the centre of a leaf on their host plant. Baffling is known to amplify the call of a male. In the first chapter of my thesis, I used data from a previously conducted mesocosm experiment to study the expression and mating success of calling and silent ARTs under varying predation risk from their natural predator, the green lynx spider (Peucetia viridans). The findings of the study showed that males were equally likely to call or remain silent on a night and the mating successes of both the ARTs were similar across a steep predation gradient. The similarity in mating success across varying ecological contexts may allow individuals to switch between them without incurring mating related costs. Furthermore, silent males were more likely to aggregate around other callers than callers themselves and obtained a majority of their matings by doing so, which suggests that silent males employ satellite behaviour. In the second chapter of my thesis, I explored the adaptive value of satellite behaviour. While literature suggests that individuals employ satellite behaviour to get mates, its relative advantage over other non-bourgeois tactics remains unexplored. Through laboratory experiments, I showed that silent males do not gain additional mating benefits by behaving as satellites, suggesting that satellite strategy may not be the only alternative tactic employed by silent males to get mates. In the third chapter of my thesis, I investigated why baffling is not commonly observed in the field given its amplification advantage over the other two ARTs, silent and calling. Using an individual-based modelling approach, I explored whether frequency-dependent, density-dependent selection or habitat structure could limit the mating success of bafflers. The results of the study showed that the co-existence of these tactics over ecological time scales is facilitated by the spatial structure of the landscape they inhabit, which served to equalize the otherwise unequal mating benefits of the three tactics. In the last chapter of my thesis, I explore the mortality costs of the two ARTs due to predation. Through laboratory experiments using the green lynx spider as the predator, I showed that the three ARTs elicit a very low but similar likelihood of being attacked and the mortality costs related to these attacks are negligible. The findings suggest that the three ARTs are mildly vulnerable to predation by their natural predator. In summary, my thesis demonstrates that the ARTs expressed by O. henryi provide similar mating benefits. The similar mating benefits of the ARTs and negligible mortality costs due to predation may allow O. henryi males to maximise fitness in varying ecological conditions.

Prey traits that facilitate matings and help forage are shaped by a combination of sexual selection and natural selection as they also tend to attract predators. At the ecological scale however, prey individuals manage this predation risk by altering conspicuous traits and behaviours leading to adverse fitness consequences. Therefore, predicting any evolutionary change as an outcome of risk management requires an understanding of the underlying mechanisms governing predator-prey interactions. By developing and addressing theoretical predictions using empirical evidence collected with a combination of field experiments, enclosure experiments, and computer simulations I investigate the following research themes: (a) predation cost of mate searching and fitness consequences of prey defence responses (space use and alternative reproductive tactics), (b) scaling up of individual prey responses to emergent population mating patterns (assortative mating), and (c) the role of habitat choice in potentially structuring populations through assortative mating. Having examined species interactions at individual- and population-level, I then go on to integrate these ideas along with climate into an ecosystem-level framework, to (d) investigate the role of animals in litter decomposition across a precipitation gradient. Based on these results, I develop a framework and link it to my short- and long-term plans which include unifying prey responses in the context of foraging and reproduction, phenotype-environment matching, effect of climate on species interactions, and ecosystem function.

Convergent evolution of traits is a common feature across the tree-of-life. However, only certain taxonomic groups repeatedly evolve a specific suite of traits and very little is known about why this is not widespread. In ants, one such complex trait is polygyny (multiple-queen colonies) which has evolved repeatedly from an ancestral phenotype of a monogyne(single-queen colony).  Polygyny results in large supercolonies made up of unrelated workers and several behavioural, morphological, and life history modifications. I will talk about my postdoctoral work examining the genomic basis of such a trait in the desert ants from Israel, where both these traits are found in a single population. I find that differences in the number of queens is associated with the presence of a supergene, a large non-recombining region of a chromosome that codes for a complex trait, much like a sex chromosome. I then discuss how this supergene is inherited, maintained, and possibly introgressed into other lineages. Finally, we look at how conserved this region is and hypothesize about the genomic basis for repeated evolution of such traits.

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.