Phages, or viruses that infect bacteria, are often seen as perfect predators: they hijack their host's cellular machinery to replicate, ultimately killing the host to release new viral progeny. However, certain (temperate) phages can also initiate lysogeny—a latent infection where the viral genome integrates into the host genome, forming a prophage which replicates when the host cell divides. While lysis is an antagonistic host-parasite interaction, lysogeny can be viewed as mutualistic.

Although one might expect lysis to confer higher fitness to the virus due to rapid offspring production, lysogeny remains prevalent across diverse ecosystems, including oceans, soil, and host-associated microbiomes. For instance, conservative estimates suggest that about a fifth of marine bacterial cells harbor prophages. This prevalence highlights the need to understand the ecological drivers of being temperate and the influence of lysogeny on microbial communities.

In this talk, I will first present a theoretical framework for comparing the fitness of lytic and lysogenic viral strategies. I will discuss past work that identifies conditions where lysogeny can outperform lysis in the short-term. Additionally, I will introduce a mathematical framework I developed to explore the eco-evolutionary dynamics of temperate phages over the long-term. In particular, I will demonstrate how periodic environmental changes, such as diurnal or seasonal shifts, can create conflicting selection pressures on different timescales, which ultimately favor intermediate strategies between obligate lysis and obligate lysogeny. Finally, using an environmentally relevant phage-bacteria system, I will show how lysogeny affects microbial communities by enabling multiple phages to coexist with a single host population, in apparent violation of the competitive exclusion principle.

There is an unprecedented urgency in mitigating the impacts of climate change and forest restoration strategies are at the forefront. Global and national scale environmental policy fora have championed the cause of forest restoration as an important nature-based solution, culminating in the UN Decade of Ecosystem Restoration. Also, it has often been touted as a cost-effective and scalable panacea with the potential to deliver a variety of benefits beyond sequestration of carbon. However, the reality of this strategy is complex. In this talk, I will weave the opportunities and realities of forest restoration as a viable strategy for climate change mitigation and other ecosystem benefits in India. I will highlight the potential of forest restoration as a ‘Natural Climate Solution’, the realities of forest restoration in areas that climatically host savannas and forests and the trade-offs and synergies in Nature’s Contributions to People from forest restoration programs across India

Accelerating climate change as a result of anthropogenic activities continues to have a profound impact on ecosystems worldwide. Particularly vulnerable are the thermally sensitive flora and fauna of tropical mountains. Mountain ecosystems can therefore serve as in situ models to study the effects of climate change on biological communities. While innumerable studies have reported local extinctions of species and overall loss of biodiversity from across the globe, loss of biotic interactions also deserves attention. One of the most striking examples of networks of multi-species interactions is exemplified by mixed species flocks (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. In this study, I examine how the composition and properties of MSF networks change along an elevation gradient. We observe a general decline in network structure with increasing elevation with some anomaly at around 1600m. I also attempt to correlate the composition of arthropods (such as flying insects, foliage insects) with the composition of MSF in terms of species with different foraging techniques.

Ants are ubiquitous, hyper-diverse, and one of the oldest venomous arthropods on earth. They belong to the order Hymenoptera, which also includes sawflies, bees, and wasps. Ants, wasps, and bees share a common ancestor – a stinging wasp-like organism – and constitute the aculeata lineage. In Hymenoptera, females have modified their ovipositor into a stinger, which is connected to the venom gland, Dufour’s gland, and, in queens, to the ovaries. Venom, a cocktail of proteins, peptides, salts and amino acids, is an adaptive trait in certain organisms to fulfil their function like predation, defence from predators and microbes, and competition.  

While several venomous arthropods, such as wasps, scorpions and spiders, have been studied due to their medical relevance, ant venom cocktails are relatively untapped. Most studies on hymenoptera venoms are restricted to honeybees and wasps, while very few have focused on a handful of ant species, such as fire ants and giant red bull ants. My thesis aims to investigate Indian ants and shed light on their enigmatic and unexplored venoms.

My first chapter employs a proteo-transcriptomic approach to explore the venom of Indian ants: Tetraponera rufonigra (Bi-coloured arboreal ant), Myrmecaria brunnea (Brown Hunchback ant), Leptogenys processionalis (Razorjaw ant), and Diacamma indicum (Indian Queenless ant). These ant species were selected considering their habitat, ecological function, and evolutionary position. This chapter will unveil the composition of venom and how it is shaped by its deployment in distinct ecological contexts.

Seasonality is a major driver for several traits in arthropods, mainly due to their inability to maintain homeostasis, unlike vertebrates. The second chapter focuses on the plasticity of ant venom. By integrating proteo-transcriptomics and free amino acids profiling, this chapter will examine how seasonal changes influence venom composition and amounts. These findings will reveal how ants modify their venom cocktail to survive and thrive in fluctuating environmental conditions.

Eusociality, the division of labour within a colony, has evolved multiple times in the animal kingdom and has underpinned the evolutionary success of several lineages. An ant colony is divided into different casts like queen, worker (in some cases, major and minor workers) and drone. My third chapter will attempt to investigate the intra-colony venom variation across different working classes (casts). The results of this chapter will elucidate the influence of task specialisation on ant venoms.

Together, my thesis provides the first comprehensive analysis of Indian ant venom composition, highlighting its ecological, seasonal, and evolutionary dynamics. This study will open new avenues for future exploration in ecology, evolution, and biodiscovery research.

Ants are ubiquitous, hyper-diverse, and one of the oldest venomous arthropods on earth. They belong to the order Hymenoptera, which also includes sawflies, bees, and wasps. Ants, wasps, and bees share a common ancestor – a stinging wasp-like organism – and constitute the aculeata lineage. In Hymenoptera, females have modified their ovipositor into a stinger, which is connected to the venom gland, Dufour’s gland, and, in queens, to the ovaries. Venom, a cocktail of proteins, peptides, salts and amino acids, is an adaptive trait in certain organisms to fulfil their function like predation, defence from predators and microbes, and competition.  

While several venomous arthropods, such as wasps, scorpions and spiders, have been studied due to their medical relevance, ant venom cocktails are relatively untapped. Most studies on hymenoptera venoms are restricted to honeybees and wasps, while very few have focused on a handful of ant species, such as fire ants and giant red bull ants. My thesis aims to investigate Indian ants and shed light on their enigmatic and unexplored venoms.

My first chapter employs a proteo-transcriptomic approach to explore the venom of Indian ants: Tetraponera rufonigra (Bi-coloured arboreal ant), Myrmecaria brunnea (Brown Hunchback ant), Leptogenys processionalis (Razorjaw ant), and Diacamma indicum (Indian Queenless ant). These ant species were selected considering their habitat, ecological function, and evolutionary position. This chapter will unveil the composition of venom and how it is shaped by its deployment in distinct ecological contexts.

Seasonality is a major driver for several traits in arthropods, mainly due to their inability to maintain homeostasis, unlike vertebrates. The second chapter focuses on the plasticity of ant venom. By integrating proteo-transcriptomics and free amino acids profiling, this chapter will examine how seasonal changes influence venom composition and amounts. These findings will reveal how ants modify their venom cocktail to survive and thrive in fluctuating environmental conditions.

Eusociality, the division of labour within a colony, has evolved multiple times in the animal kingdom and has underpinned the evolutionary success of several lineages. An ant colony is divided into different casts like queen, worker (in some cases, major and minor workers) and drone. My third chapter will attempt to investigate the intra-colony venom variation across different working classes (casts). The results of this chapter will elucidate the influence of task specialisation on ant venoms.

Together, my thesis provides the first comprehensive analysis of Indian ant venom composition, highlighting its ecological, seasonal, and evolutionary dynamics. This study will open new avenues for future exploration in ecology, evolution, and biodiscovery research.

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.