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.

Movement in organisms is driven by multiple factors, foremost among them the need to acquire resources in spatially structured environments where resources are unevenly distributed. However, ecological communities are defined by the ubiquity of species interactions—ranging from competition and predation to mutualisms—which fundamentally shape the decision to move and thereby influence the evolution of motility. In species engaged in cross-feeding mutualisms (CFMs), where partners exchange benefits via the environment, the adaptive value of motility becomes especially complex. While motility can enhance resource acquisition, it also carries the risk of displacing individuals away from their mutualistic partners—regions typically rich in resources—and imposes metabolic costs associated with flagellar construction. Using a spatially explicit, mechanistic model of mutualism, we demonstrate that selection for or against motility depends on: 1) the motility status of the partner, 2) the production and uptake rates of cross-fed resources, and 3) the magnitude of motility-associated costs. We further test our simulation outcomes with experimental data from a microbial CFM involving Escherichia coli and Salmonella enterica. Our results reveal that while motility is consistently favored in S. enterica irrespective of E. coli’s motility, the selective pressure on motility in E. coli is contingent upon whether its partner is motile. This study underscores how the pervasive nature of species interactions in ecological communities plays a crucial role in shaping the evolution of bacterial motility.

This lecture will cover the foundational elements of eco-evolutionary dynamics, providing an overview of the key components involved in modelling population and evolutionary processes. It will introduce core concepts related to quantitative phenotypic traits and explore how these traits link to population and community dynamics. The lecture will also discuss essential principles of quantitative genetics, the assumptions underlying these models, and how evolutionary dynamics emerge and feedback to influence population dynamics. Serving as an introduction, this lecture will act as a basic guide that will go through the steps required to develop a simple eco-evolutionary dynamical model.

Individual trait variation is ubiquitous in nature and is central to populations involved in complex interactions with others in an ecological system. Such variation drives eco-evolutionary dynamics, shaping how populations and communities respond to environmental perturbation. In this talk, I will provide an overview of how individual variation can scale up to influence the stability, predictability, and resilience of populations to environmental perturbation, as well as the recovery dynamics of collapsed ecological communities. Furthermore, I will explore how individual trait variation, which is critical to species interactions within complex ecological networks, can dynamically evolve in response to changes in interaction strength, environmental perturbation, and network architecture. This consequently impacts how complex communities respond to changes in the environment. Lastly, the talk will highlight the importance of incorporating the adaptive nature of species interactions such as rewiring, eco-evolutionary feedbacks, and dynamic resilience frameworks to better understand the responses of complex communities to environmental change.

The research questions explored by Earth scientists, though they may not initially seem directly relevant to ecological research, can ultimately yield valuable insights for the field of ecology. In this presentation, I will illustrate this with two examples. First, our investigation into the sulfur isotopic composition of rocks, and later bird feathers, not only provided insights into bird migration patterns but also helped identify the sulfur source in the part of the food chain. In this section, I will present the results of sulfur isotopic variability in the feathers of both resident and migratory birds in India. The latter part of the talk will focus on the biogeography of tree structures at the landscape scale in the Western Ghats. This research challenges the assumption that asymmetric heating—often responsible for vegetation distribution in mid-latitudes—does not apply in the Western Ghats due to its lower latitudinal position. The study emphasizes the significant role of the monsoonal climate and asymmetric solar heating in shaping tree structure in the region

Soil microorganisms are the unseen majority in soil, that drive critical ecosystem processes, such as biogeochemical cycling of nutrients. For growth and metabolism, microbes require nutrients, which are either readily available as simple compounds or locked within complex macromolecules. To access these nutrients, microbes secrete extracellular enzymes into the soil matrix. This study focuses on three widely studied enzymes: β-glucosidase (BG, carbon-acquiring), N-acetyl-β-Glucosaminidase (NAG, nitrogen-acquiring), and phosphatase (AP, phosphorus-acquiring). Soil enzyme activity exhibits substantial spatial heterogeneity. To investigate the abiotic factors regulating enzyme activity at larger spatial scales, I compiled data from 54 published studies reporting enzyme activity in natural soils. I examined the effects of biome, edaphic factors (pH, organic carbon [SOC], total nitrogen [TN], total phosphorus [TP]), climatic factors (mean annual temperature [MAT], mean annual precipitation [MAP]), and geographic factors (elevation). Our results revealed that N-acquiring enzymes showed no significant differences across biomes, suggesting widespread nitrogen limitation. Conversely, C- and P-acquiring enzymes exhibited the lowest activity in desert soils, likely due to moisture limitations.

C acquiring enzyme activity was negatively affected by MAP, suggesting reduced carbon acquisition in wetter conditions, while SOC had a positive influence. NAG activity also decreased with increasing MAP but was positively influenced by elevation and TN, indicating enhanced nitrogen acquisition at higher elevations and with greater nitrogen concentrations in soil. For P acquiring enzyme, elevation and soil pH had negative effects, with reduced phosphorus acquisition at higher elevations and in more alkaline soils, whereas SOC positively influenced P acquiring enzyme activity. This study highlights the complex interplay of biotic and abiotic factors regulating soil enzyme activity across spatial gradients. Further research could explore additional factors or interactions to refine our understanding of microbial contributions to nutrient cycling.

This lecture explores the innovative use of Lab-on-a-Chip (LOC) technologies in conservation and environmental applications. LOC devices, which miniaturize laboratory processes onto a single chip, offer rapid, cost-effective, and portable solutions for monitoring ecosystems, and conserving biodiversity. The presentation will cover the integration of microfluidics, sensors, and bioanalysis for real-time environmental data collection, highlighting their potential in addressing global challenges. Case studies demonstrating the impact of LOC in wildlife conservation, and ecosystem monitoring will also be discussed.