Recent genetic research has shown that the present-day population of the Indian subcontinent derives its ancestry from at least three major sources: early agriculturalists from the Iranian plateau, pastoralist groups originating in the Pontic-Caspian steppe, and ancient hunter-gatherers with affinities to the Andamanese. The current genetic landscape of India represents a cline resulting from admixture among these sources. However, with growing availability of ancient and modern genome sequences and advanced population structure analyses, a more nuanced picture of ancestry is beginning to take shape.
In this study, we focus on Dravidian-speaking populations and propose the existence of a fourth ancestral component. This component appears to have diverged from the basal Middle Eastern lineage that contributed to the Iranian agriculturalist ancestry. Supported by the Elamo-Dravidian hypothesis and linguistic phylogenies within the Dravidian language family, our genetic findings suggest a coherent link between language and ancestry.
Our analyses identify this unique ancestry—termed ‘Proto-Dravidian’—within the Koraga tribe, suggesting its emergence around the early period of the Indus Valley Civilization. This ancestry is genetically distinct from the previously described sources and is estimated to have originated at least 4,400 years ago in the region stretching between the Iranian plateau and the Indus Valley. The presence of this component across contemporary Indian populations, with the exception of some tribal groups, underscores its enduring influence.
This discovery highlights the critical role of fine-scale, population-specific studies in reconstructing ancestral histories. It also calls for carefully designed sampling strategies in genomic biobanking to avoid oversimplified models of ancestry. Moving forward, an interdisciplinary approach will be essential to unravel the complexities of human population history in South Asia.

Metabolicaly-driven interactions between biological species in any local ecosystem typically form large, complex networks that generate interesting and often unpredictable system dynamics. A new Mount Everest for theoretical biology, with a wide range of applications, is the development of methods to control and engineer these complex, nonlinear systems. To this end, we need to understand a fundamental problem that has occupied Biologists, and in particular, Ecologists, for almost two centuries: how do these seemingly improbable systems assemble and persist in (an increasingly) fluctuating and uncertain real world? In this talk, I will outline the challenge, and present recent progress towards the goal of engineering microbiomes under a ubiquitous source of environmental fluctuations: temperature.

Elevational migration is the seasonal movement of organisms between higher-elevation breeding grounds and lower-elevation wintering grounds. Amongst montane bird species, elevational migration is a common phenomenon, with nearly 70% of high elevation species in Himalayas showing this behaviour. Yet, most bird migration studies focus on long-distance latitudinal migration and most of our current understanding of elevational migration and it’s drivers come from studies from neotropical mountains where most migrants are frugivorous, unlike the mostly insectivorous migrants of the rest of the world. I aim to understand how birds migrate in the Himalayas and how resource availability and dietary specialisation can explain elevational migration in Himalayan Birds.
In the first chapter I use a large citizen science dataset (eBird) to determine the sumer and winter elevational ranges of 377 Himalayan bird species and describe five elevational migration patterns. I then examine how diet, habitat, territoriality, mass and wing morphology can best explain these patterns.
In the second chapter I attempted to understand how arthropod availability varies seasonally along the Himalayan elevation gradient. Aerial and terrestrial arthropods decline with elevation in the winter but increase with elevation in the summer while foliage arthropods show a similar mid-elevation peak in abundance across seasons. I then correlate these patterns with the abundances of different functional guilds of birds to determine of food availability may drive elevational migration.
In the third chapter, using a combination of faecal DNA metabarcoding and stable isotope analysis, I examine whether dietary specialisation can explain why some high elevation breeding birds migrate to lower elevations in winter (where arthropods abundances do not fluctuate) while others overwinter at high elevations winter despite the lack of arthropod resources.
In summary, using a combination of citizen science datasets, field and lab-based methods, my thesis attempts to improve our understanding of elevational migration in the Himalayas and the drivers of this movement. Understanding how temperature, seasonality and diet drive altitudinal migration will be a crucial first step in predicting how tropical montane avifauna will fare in an increasingly warm world.

The distribution of plants and animals across the globe raises a key question: why are species found where they are, and why not elsewhere? To attempt this roughly 200-year-old question requires the study of different ‘levels’ – for instance, from how the population density (the abundance) of a species is structured across its range to how the extent of a species’ occurrence (the range) influences large-scale patterns of species richness. This PhD aims to understand the macroecological patterns and processes of species diversity and distribution using a three-layered approach.

At the largest level, what drives patterns of species richness? For the first two chapters, we build simulation models to understand i) the influence of range properties on cross-taxa species richness patterns and ii) how eco-evolutionary processes drive extant range and richness patterns.

Given that species can be rare along two dimensions, namely abundance and range size, which traits determine rarity? In the third chapter, we study how the interactions between habitat specificity, habitat availability and competition affect the abundance and range sizes of woody plants of the Western Ghats.

At the smallest level, what influences the distribution of abundance across a species’ range? In the final chapter, we attempt to understand the spatial patterning of abundance of select woody plants of the Western Ghats using a combination of modelling and field surveys.

Overall, this thesis will provide new insights into patterns of richness, range size and abundance and their underlying drivers in tropical biodiversity hotspots.

Mutualism involves exchange of services and rewards between partners, resulting in a net benefit to those involved. In many mutualisms, hosts are larger partners that interact with several individuals of smaller mutualists that live on or within them and are termed symbionts. Partners have an incentive to cheat, leading to possible breakdown of the mutualism. Hosts may regulate interaction by selectively rewarding cooperative symbionts. However, this host-centric view that has dominated mutualism studies, does not explain the role of symbionts in regulating trade within a mutualism. In a mutualism with physiological connection between the host and the symbionts, it is necessary to understand whether the symbionts can influence the resources they receive from hosts. My thesis is an attempt to understand resource allocation patterns and the strategies employed by both partners in a prominent brood-site pollination mutualism between fig trees and their pollinating fig wasps which develop within an enclosed inflorescence termed a syconium.
We determined the pattern of resource partitioning to different components of the fig syconium. We tested the applicability of theories describing resource allocation at the whole plant level to individual organs like the syconium. Results show that the syconial wall, that provides protection to occupants, makes up the majority of the dry mass of a syconium, although it is nutritionally less demanding. Further, a single pollinator wasp is costlier to produce compared to a single seed. We showed that there is no number–mass trade-off for both seeds and pollinator wasps indicating proportional allocation of resources to a syconium.
We measured the elementome of seeds, pollinators and the syconial wall tissue and determined the biogeochemical niche (BN) of syconium occupants by examining concentrations of many important elements. We found that the BN of seeds and pollinators are significantly different suggesting differential nutrient demands and demonstrating how coexistence is possible for seeds and pollinators within the syconium microcosms.
We attempted to understand if individual differences in composition of seeds and pollinators result in differential allocation of resources to the syconium. We experimentally manipulated pollinators (foundresses) to produce syconia containing only seeds (S), only pollinators (G) and both seeds and pollinators (SG). We found that overall, the presence of both seeds and pollinator galls increased resource
allocation to a syconium. Since pollinators are gallers, we attempted to understand the role of plant growth hormones in the differential effects of seeds and pollinators on resource allocation. We measured the concentrations of indole-3-acetic acid (IAA), an auxin and trans-Zeatin (tZ), a cytokinin, in S, G and SG syconia during early and mid-phases of their development. We found that IAA and tZ concentrations did not differ between S and G syconia suggesting that galls mimic seeds to garner resources. Further, SG syconia had higher hormone levels correlating with its increased size reported in the previous chapter. Syconia that contain both seeds and galls are rewarded with more resources, which can also ensure cooperation between the partners.

It’s true that having first aid training undoubtedly helps save lives. That’s not all though; giving appropriate first aid immediately can help to reduce a person’s recovery time and make the difference between the patient having a temporary or long-term disability. Not all accidents, injuries or illnesses require a trip to the hospital but it doesn’t mean they don’t cause pain and suffering to the patient, even just by employing simple techniques such as applying an ice pack correctly, or utilising appropriate bandaging, you’ll help to relieve their discomfort. First aid training will make you confident and comfortable and therefore more effective and in control when you need to be.

Urbanisation and its major consequences, Artificial Light at Night (ALAN) and traffic noise, have significantly impacted habitat utilisation, diet, and behaviour of animals, particularly nocturnal species, including owls.

The dynamic play of attraction and avoidance in response to ALAN and traffic noise will influence the habitat utilisation. To explore the same, my first chapter aims to investigate the space use by a nocturnal top predator, Athene brama (spotted owlet) in relation to ALAN and anthropogenic noise, across an urban-rural gradient at different spatial scales, using bioacoustics as a tool.

For my second chapter, I aim to determine the diet of A. brama along an urban-rural gradient. Firstly, I will ascertain the prey availability under lit and unlit conditions across an urban-rural gradient. Thereafter, to understand their diet composition, I will be using the pellet analysis method. In contrast to the urban centric nature of previous studies, effects in adjacent rural areas will be a novel aspect in the present study.

The third and final chapter will focus on the foraging behaviour of A. brama. The initial part will consist of focal animal sampling in foraging grounds of owlets to understand their various behaviours, eventually leading to performing manipulative behavioural experiments in the wild to determine their means of prey detection in lit and unlit conditions.

This study will enhance understanding of how urbanisation influences nocturnal predators and their adaptability in these changing landscapes.

Macroevolution provides a lens to investigate how species originate, adapt, diversify, respond to environmental changes and go extinct. My doctoral thesis leverages tarantulas (Family Theraphosidae) as a model system to explore these questions, weaving together biogeography, trait evolution, morphology, and climate to understand the forces shaping biodiversity patterns.
The first chapter reconstructs the complex biogeographic history of tarantulas, addressing the paradox of decoupled centers of origin and diversity. Using fossil-calibrated phylogenies and ancestral range reconstructions, it reveals how plate tectonics and dispersal events sculpted their global distribution, refuting the classical “centrifugal” model of speciation.
The second chapter examines the drivers of asymmetric species richness in tarantula subfamilies. Disentangling the effects of evolutionary time and trait-driven diversification, it demonstrates how defensive innovations, such as urticating hair, increase diversification rates. By empirically testing the “escape and radiate” hypothesis alongside alternative models, this chapter offers insights into how traits drive long-term biodiversity patterns.
The third chapter explores the interplay between morphology and ecology, focusing on miniaturization. It links shifts to non-burrowing terrestrial microhabitats with reduced body size and altered limb proportions, illustrating how ecological opportunity can catalyze morphological evolution. Defying Cope’s rule, this study emphasizes the role of niche shifts in driving body size reduction.
The fourth chapter investigates the impact of recent climate change on tarantula genetic diversity and niche dynamics. By integrating genetic analyses with species distribution models projected across past climates, it reveals how environmental changes since the Last Glacial Maximum have shaped population structures. The findings underscore the vulnerability of biodiversity to rapid environmental shifts, bridging ecological and evolutionary perspectives on climate change.
Together, these chapters address core themes in macroevolution, including the roles of geography, traits, ecological transitions, and environmental change in shaping biodiversity. By contextualizing tarantulas within broader eco-evolutionary frameworks, this thesis offers insights into how life diversifies and adapts, with implications for addressing the global biodiversity crisis.

Sexual signalling is a fascinating aspect of animal communication, involving stereotypical behaviors that secure mating opportunities. In many species, individuals employ multiple alternative reproductive tactics (ARTs) to achieve reproductive success. These tactics may be fixed or flexible—the latter being context-dependent—and can be influenced by physical, ecological, physiological, or social factors. In species with socially flexible ARTs, individuals adjust their behavior based on the surrounding social environment. As sexual signals traverse the environment to reach potential mates, they are simultaneously detected by competitors and sneakers.
In my thesis, I examine the social dependence of ARTs using Oecanthus henryi as a model. O. henryi, is a tree cricket native to Peninsular India and Sri Lanka, typically found on the host plant Hyptis suaveolens. Males produce a calling song by rubbing their wings, and the females exhibit phonotaxis towards singing males. Males employ four distinct alternative reproductive tactics: (i) calling, where a male sings while perched on a leaf lamina or edge; (ii) baffling, in which a male constructs a baffle on the leaf surface—shaped like his wings—to amplify his call by reducing destructive interference; (iii) silent strategy, where the male does not sing; and (iv) satellite strategy, characterized by a silent male moving towards a caller or baffler.
In the first chapter, I explore how the presence of conspecific acoustic signals influences the adoption of ARTs through playback experiments that vary the number and intensity of these signals. In the second chapter, I investigate how physical interactions with conspecific males affect tactic expression by manipulating competitor presence. In the third chapter, I assess the impact of the adopted ART on male reproductive success via controlled mating experiments. Overall, my work explores how competition shapes alternative reproductive tactics and the influence of alternative tactic adopted on reproductive outcomes.

Alternative reproductive tactics (ARTs) are distinct phenotypes that individuals of a species use to maximize reproductive success. This thesis investigates the persistence and adaptive value of flexible ARTs in male tree crickets, Oecanthus henryi, which employ calling, remaining silent, and baffling (calling through a hole in a leaf to amplify sound) to attract mates. By examining the impact of predation risk, the effectiveness of satellite behaviour, the uncommon use of baffling despite its advantages, and the mortality costs associated with different ARTs, this research aims to understand how these tactics coexist and maintain similar fitness benefits across various ecological contexts.
In the first chapter, I briefly introduce the subject of alternative reproductive tactics, their various modes of expression and their persistence in natural populations. I draw attention to the general lack of understanding concerning the fitness components of flexible ARTs. I highlight various factors that can affect the fitness of ARTs. I introduce the model system Oecanthus henryi and justify its use for studying flexible ARTs. Using data from a mesocosm experiment, the second chapter explores how predation risk from the green lynx spider (Peucetia viridans) affects the expression and mating success of calling and silent ARTs. The results show that males are equally likely to call or remain silent regardless of predation risk, and both tactics result in similar mating success. Silent males often aggregate around callers, potentially employing satellite behaviour to gain mates. The third chapter examines the adaptive value of satellite behaviour through laboratory experiments. It was found that silent males do not gain additional mating benefits by acting as satellites, suggesting that this may not be the only alternative tactic for silent males to obtain mates.
Despite its amplification advantage, baffling is rarely observed in the field. Using individual-based modeling, the fourth chapter investigates whether frequency-dependent and/or density-dependent selection, or habitat structure, limits the success of bafflers. The findings indicate that spatial structure of the habitat helps equalize mating benefits among the three tactics, facilitating their coexistence over time. The fifth chapter assesses the predation risks associated with the three ARTs. Laboratory experiments reveal that all three tactics have low and similar likelihoods of being attacked by green lynx spiders, with negligible mortality costs.
      The thesis concludes that the similar mating benefits and low mortality costs associated with the ARTs allow Oecanthus henryi males to switch between tactics without incurring significant fitness losses. This flexibility helps maximize reproductive success in varying ecological conditions, supporting the persistence of flexible ARTs in this species.