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.

Studying foraging behaviour unlocks access to the strategies used by organisms to optimize to the environment within the limits of constraints, and thus adapt to their environment. It uncovers information from an individual level to higher orders of organizations; how to optimally use the landscape and how energy flows across in its ecosystem. I intend to explore the foraging ecology of the tropical bat, Megaderma spasma from multiple perspectives; viz. the hunting behaviour, the energetics; and the encounter with its prominent prey species, Onomarchus uninonatus.

In my first chapter, I try to decode the animal behaviour from movement data, and characterise the bat hunting strategy. The high resolution data from bat-borne biologgers include IMU sensor, GPS and audio recorder. We intend to use the multimodality of the data to cross-check the behaviour signals across the data types. From the GPS data, I intend to understand the bat preference for forest patches.

In the second chapter, I explore the bat energy loss and gain in its active duration, and intend to put it in a theoretical perspective for better syntax to understand the energy efficiency for a bat. Understanding the bat strategies is our key to understand how evolution solved the problem of high energy demands. Instead of delving into the physiological aspect, I try to understand the bat foraging behaviour in the context of energetics, from the data collected from the biologgers.

In the third chapter, I aim to combine the database collected over the years about Megaderma spasma and Onomarchus uninonatus to computationally estimate the encounter rate in the wild.

Functional diversity estimated from species’ traits reflects their morphological, physiological, and ecological roles and their influence on ecosystem functioning and provides a link between species diversity and ecosystem processes. Understanding how functional diversity varies along environmental gradients can help us elucidate the species-trait-environment relationship and the underlying processes governing species communities. Richness-based measures, such as the number of species, have long been used to understand various aspects of global change, such as climate change, land use change, invasive species, etc. However, they do not provide much information about the consequences for ecosystem functioning. Functional trait-based approaches can offer insights into ecosystem functions and the structure of communities. I will use functional diversity and trait-based approaches to understand how ground-dwelling arthropod communities vary across environmental gradients. These ground-dwelling arthropods (ants, beetles, wasps, bees, spiders, ticks and mites, centipedes, collembolans, etc.) offer opportunities to understand biodiversity patterns on how communities can respond to environmental variation.
In the first chapter, I will study how the functional diversity of communities varies along an elevational gradient (from 3700 to 5000 m asl) in the Trans-Himalayas. Here, I will examine diversity patterns in multiple taxa along this gradient that interact with ground-dwelling arthropods (e.g., plants and soil microbial decomposers). In chapter two, I will focus on a subset of species that occur along the entire gradient, i.e., wide elevational distribution. Here, I will examine intraspecific trait variation in this subset of species to determine the characteristics of their trait-and-environment relationships. In chapter three, I will evaluate how invasive species can influence the functional diversity of communities across various land-use types. Here, I will study how Anoplolepis gracilepis (yellow crazy ant)—one of the 100 worst invasive species in the world—affects the community structure of ants. I will also test the trait-similarity hypothesis to ask whether the species that co-exist with the invader are functionally differentiated.
I expect this work will provide insights into how community structure and functions vary across environmental conditions.

The stability and complexity of communities depend on an intricate network of interactions within ecosystems. Trophic food webs demonstrate interactions between producers and consumers at various levels in ecological ecosystems. A significant part of terrestrial biodiversity is plants, phytophagous insects, and their natural enemies, such as parasitoids and predators. Despite being a significant presence in terrestrial insect communities, the roles and diversity of parasitoids are not well known due to limited research on tri-trophic interactions, particularly in the tropics. In this study, I will identify and contrast plant-herbivore-parasitoid food webs within the Rutaceae family of plants across wild and cultivated environments.
Chapter 1 focuses on collecting and identifying lepidopteran herbivores (butterflies and moths) and their parasitoids on Rutaceae across multiple study sites. To determine the trophic interactions, insects must be collected during all seasons and parasitoids reared from hosts collected at all immature life stages. This chapter will also determine the life histories of each parasitoid.
In Chapter 2, I will construct and analyse the food webs on Rutaceae, from their wild native setting and under varying management practices. This will show the difference in species interaction between wild and cultivated Rutaceae, as well as the effect of agricultural practices on trophic interactions. This chapter will also identify the diet range of each consumer.
Chapters 3 and 4 are focused on experimental studies to identify the contributions of selected biotic interactions in shaping the food webs from the different sites. Chapter 3 addresses food preferences and performance of the butterflies and parasitoids. Chapter 4 addresses the impact of ant predation of the lepidoptera in the food webs.
Chapter 5 is on the application of this study to Butterfly Parks. I will develop guidelines for managing butterfly rearing at the Bannerghatta Butterfly Park and create displays about the diversity of insects on Rutaceae plants, trophic interactions amongst them in the Butterfly Park, and parasitoid natural history.
These research questions offer an integrated approach of both ecology and agriculture to understand the trophic interactions occurring in the Rutaceae plant family under a range of ecological conditions.

Fitness landscapes are a paradigm to understand how evolution proceeds. Yet such landscapes are only implicit about ecology and the diverse underlying communities in which organisms naturally thrive. In this talk, we show two concrete examples of how being part of an interacting community fundamentally alters evolutionary trajectories. Using bacterial communities as model systems, we show in one case how a species evolves in response to antibiotics depends on its interactions with another strain. In fact tuning this interaction can allow us to control how and whether antibiotic response evolves in the same environmental conditions. In the other case we show that sulfur cycling "pink berries" comprising diverse bacterial communities show remarkably slow down co-evolution due to strong mutualistic interactions in the community. In both cases, we show that simple mathematical models of community eco-evolutionary dynamics can capture our observations, and make new testable predictions. Our work highlights how ecological interactions can control evolutionary trajectories in bacterial communities.

Strikingly regular, large-scale patterns of vegetation growth were first documented by aerial photography in the Horn of Africa circa 1950 and are now known to exist in drylands across the globe.  The patterns often appear on very gently sloped terrain as bands of dense vegetation alternating with bare soil, and models suggest that they may be a strategy for maximizing usage of the limited water available.  A particular challenge for modeling these patterns is appropriately resolving fast processes such as surface water flow during rainstorms while still being able to capture slow dynamics such as the uphill migration of the vegetation bands, which has been observed to occur on the scale of a band width per century.  We propose a pulsed-precipitation model that treats rainstorms as instantaneous kicks to the soil water as it interacts with vegetation on the timescale of plant growth.  We use a stochastic rainfall model with the influence of fast storm-level hydrology captured by the spatial distribution of the soil water kicks.  The model allows for predictions about the influence of storm characteristics on the large-scale patterns.  Analysis and simulations suggest that the distance water travels on the surface before infiltrating into the soil during a typical storm plays a key role in determining the spacing between the bands. 

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.