Understanding the generation and maintenance of diversity—both in lineages and traits—is a central goal of macroevolutionary research. Hemidactylus geckos are well-suited for exploring such questions due to their remarkable species richness and trait variation. Despite their potential, studies on the broader patterns within the genus are rare. My thesis fills this gap by dwelling into key macroevolutionary processes such as biogeography, diversification, and trait evolution in Hemidactylus by utilizing various phylogenetic comparative methods.

In chapter one, I reconstruct the most updated global phylogeny of Hemidactylus geckos using coalescent and concatenation-based methods. Further, I unravel their disputed biogeographic origins and highlight the intercontinental dispersal events that may have shaped the current diversity and distribution of the genus.

Chapter two utilizes a trait-based approach to explain the contrasting pattern of species richness and distribution between Hemidactylus and its sister genus Dravidogecko. I evaluate the effect of various abiotic and morphological characters on the dispersal ability and diversification rates of these two groups.

In Chapter three, I seek to investigate the impact of habitat use on body size and morphological evolution of the genus. I use various trait evolution models to determine whether habitat filtering drives size variation, and further attempt to quantify the strength of selection.

Finally, chapter four focuses on the ecological and evolutionary dynamics of host-parasite interactions between Hemidactylus geckos and their ectoparasitic mites. I ask whether mite communities are predominantly shaped by host phylogeny or geography, and further attempt to uncover the ecological correlates of mite loads in these geckos.

These research questions thus offer a multifaceted understanding of the evolutionary forces driving the complex trajectories of such widely distributed, highly speciose taxa.

All animals behave. Behaviour allows animals flexibility in dealing with heterogeneous, dynamic environments, and a key goal of the field of animal behaviour is to understand how, when, and why animals do what they do. To better understand behaviour, we can view it as a sequence of discrete behavioural states driven by a behavioural algorithm, a set of principles based on which an animal performs behavioural decision-making. I adopt a multi-time-scale perspective to explore behavioural algorithms from three species of mammals in the wild: meerkats (Suricata suricatta), white-nosed coatis (Nasua narica), and spotted hyenas (Crocuta crocuta), whose behaviours I inferred using accelerometer data. In this talk, I will demonstrate long time-scale structure in the behavioural sequences of all collared individuals of all three study species, showing that behaviour depends on past states of the animal much more than expected from any simple (i.e., Markovian) model of behaviour. This work is likely the most detailed description of long-time-range behavioural structure in wild-living animals reported in the literature. I will then highlight specific behaviours at a slow and a fast temporal scale, considering the 24 h activity patterns of the hyenas and the moment-to-moment vigilance dynamics of the meerkats, and explore various factors, especially social ones, that influence behavioural decisions at these scales.

Globally, opportunistic scavengers, such as kites, macaques, street dogs and livestock, often partake of the human niche, showcasing variable adherence to human norms and practices. The integration of nonhuman species into modern urban settlements thus marks a significant shift in human–animal proximities, akin to the transformative impacts of agriculture. Our research in Delhi focuses on the eco-evolutionary processes that underpin cross-species co-cultural ties, with animals exploiting food subsidies from garbage and ritual feeding practices. We study how inter- and intra-specific interactions along the urban gradient give rise to behavioural innovations in response to the predictable dispersion of such food subsidies. These interactions often involve significant adaptations or co-option of behavioural and morphological traits, influencing nonhuman social dynamics and population structures. Tropical cities, where urbanisation is a continuous process, offer quasi-experimental opportunities to examine shifts in population- and species-specific socialities in aerial, arboreal, and ground-dwelling commensals. Historically, these interactions have resulted in wildlife providing important services to humans. Unfortunately, however, such interactions can also easily turn negative, such as when actions aimed at promoting nonhuman lives lead to human–animal conflict, loss of property and invaluable lives of all contestants, and the spread of zoonotic diseases. Interestingly, human–nonhuman coexistence in South Asia represents a distinctive fusion of adopted Western infrastructure and a unique Indian ethos. This talk will emphasise why transdisciplinary methodologies are indispensable to comprehend coexistence, while designing and administering vibrant and ‘animated’ tropical cities.

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. Moreover, the findings of this thesis have also provided valuable insights for developing advanced snakebite therapeutics, including broadly neutralising monoclonal antibodies against medically important toxins such as three-finger toxins and snake venom metalloproteases.

In summary, this thesis deciphers the major drivers of venom variation in two of the medically important Indian snake species by integrating the knowledge of natural history with their venom biology. Further, the study also facilitated the identification of regions where current-generation antivenoms are ineffective, thereby highlighting the necessity for developing region-specific antivenom solutions. Moreover, the study has opened promising avenues for the discovery and development of universal recombinant antibody-based therapies that will ensure standardised and effective snakebite treatment across the globe. These advancements in snakebite therapeutics have the potential to save the lives, limbs, and livelihood of India’s thousands of annual snakebite victims.

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.

Over the last decade, several studies have shown the importance of individual variation in natural populations. Theoretical ecological studies are beginning to incorporate trait variations in models, but they continue to be largely ignored in the context of ecosystems that exhibit alternative stable states. We study the role of trait variation in the context of a bistable ecological system, specifically a savanna-woodland system. In the first chapter, we begin with a mean-field model of bistable savanna-woodland system and then introduce trait variation in functional and demographic traits of savanna trees and saplings in the model. Our study reveals that higher trait variation reduces the extent of bistability in the system, such that the woodland state is favored; i.e. woodland occurs over a wider range of driver values in comparison to the grassland state. We also find that the shift from one state to another can become less or more drastic, depending on the trait which exhibits variation. Interestingly, we find that even if the overall tree and grass cover remain insensitive to different initial conditions, the steady-state population trait distribution can be sensitive to these conditions.  

In the second chapter, we formulate a spatially explicit model of the savanna-woodland bistable system. Local interactions can vary with space, and can also change the stability landscape of dynamical systems. Fire events in savanna are also an important spatial process as they rely on the connectivity of fuel to spread in the system. Savannas also experience strong seasonality with a wet and dry season, fires being a prominent occurrence during the dry season. We incorporate these realistic features of fire and seasonality in our model along with two different demographic stages of savanna species. When comparing the spatial model to the mean-field approximation of the spatial model, we find that grassland state exists for a larger range of driver values, as short-range dispersal limits the spread of savanna species in the system. We find that fire leads to bistability in the system with grassland and woodlands as alternative stable states, while savanna state occurs as a transient state. We also find that irrespective of the initial flammable cover, the proportion burnt area depends on the flammable cover before the dry season, which depends on the wet season processes.  

In the third chapter, we introduce trait variation in the spatial model to understand its role. We find that among all savanna species types, the fittest individual survives, while other types get eliminated from the population. The dynamics followed by the system with variation is same as the dynamics of a system with only the fittest individual. 

Our findings suggest that individual variation in bistable ecological systems may have important consequences for both ecological and evolutionary dynamics and management practices. 

I joined PhD without knowing anything other than that I would learn and do research on behavioral ecology from the best place in India, completely oblivious to what it takes to do a PhD and what I would do after. This journey has been nothing short of a roller-coaster, filled with life-changing learning and pivotal shifts - both in my professional and personal life.

In this talk, I will unravel the layers of my experiences, highlighting the most essential insights I gained through navigating the academic landscape during my PhD and post-doc, then shifting to the EdTech industry, and importantly, developing life philosophy while embracing the bitter-sweet aspect of continuous learning, aimed at gearing up for long-term goals. From learning English as an initial PhD challenge to strategically selecting my postdoctoral lab, and eventually transitioning into the EdTech industry, each phase imparted invaluable lessons on balancing learning, work, personal and social life, as well as mental and physical health. I will also discuss the knowledge I wished I had at various career junctures which would help me to avoid several setbacks. I will conclude by giving an overview of my current role at LabXchange, a free-to-use web-based educational platform, alongside my projections for the future of research on animal behavior and education in this new era of artificial intelligence.

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.