A central question in ecology involves understanding the processes underlying patterns in population abundance and the distribution of species at small and large spatial scales. The distribution of individuals of a species across a landscape may be influenced by both local factors, such as resource abundance; and by landscape-level factors, such as the size of habitat patches, connectivity between patches and the permeability of the matrix surrounding habitat patches, all of which influence the colonisation and extinction of local populations and the movement of individuals between populations. How these local and landscape-level factors affect the distribution of a species may vary widely between species, because the response of species to these ecological conditions may depend on species-specific traits, such as body size, behaviour and other functional traits. There is relatively little known about how ecological factors interact with functional traits to influence species distribution in a landscape. I investigated the ecological processes at local and landscape levels influencing population densities by taking a behavioural ecological approach and using butterflies as a model system. I also examined how functional traits affect the relationships between ecological factors and species distribution in a landscape. I first examined how resource dispersion, an important ecological condition affecting butterfly populations, affects key behavioural decisions of butterflies. Studying the behaviour of individuals allows us to link population patterns with underlying ecological and evolutionary processes. I describe how butterflies appear to respond to resource dispersion at both small and large spatial scales and to balance acquiring two distinct types of resources when making foraging and habitat-use decisions. I then examined how landscape-level factors, specifically patch size, connectivity and matrix permeability, affect butterfly populations. I tested whether the apparent response of a species to landscape-level factors was affected by species-specific traits, specifically whether it was a habitat generalist or specialist and how permeable the matrix was to it. Finally, I test and describe how diverse functional traits, including morphological, life-history and behavioural traits, affect relationships between landscape composition and population density patterns of butterflies.

Large herbivores can selectively feed on nutrient rich resources, resulting in regular deposition of high quality organic matter in the form of dung. In tropical forests such as in southern India it is estimated that large herbivores contribute to several hundred kilograms of dung on a daily basis. Decomposition of this dung and its implications on nutrient cycling in an ecosystem, has recently become a subject of interest to ecologists across the globe. However, most of our understanding on dung decomposition and its implication come from agroecosystem studies conducted on cattle dung. The identity of primary insect communities involved in dung comminution and feeding is well documented, but little is known of the processes and their impact on nutrient and carbon dynamics. We had set out with three primary objectives: 1) To identify the dung feeding insect communities, 2) Quantify the changes in dung composition during the decomposition and 3) Identify the impact of dung beetles on nutrient leachate and organic matter inclusion into the soil. To address these objectives, we carried out in-situ and ex-situ experiments in a tropical forest of southern India, the Mudumalai national park, for three large herbivores- elephant, gaur and cheetal, that constitute the major herbivore biomass of the region. We found two insect communities, termites and dung beetles, actively feeding on dung. However, their community composition, diversity and abundance varied with the age of the dung and the seasons. During the course of the experiments, we found that crude carbon is readily reduced but remains unaffected by seasons and across the three forest types (dry thorn, dry deciduous and moist deciduous) of the study area. We also analysed the recalcitrant component of carbon, lignin and easy to degrade, monosaccharides to understand what forms of carbon may be reduced in this process. Monosaccharides remained unaffected during the experiments, but lignin was reduced across habitats and seasons. The final experiment looking at the leachates from dung into the soil showed considerable difference between the herbivore dungs, but no effect of the dung beetle activity compared to the controls. To our knowledge, this study is among the first to use a comprehensive approach to study dung decomposition and its impact on nutrient and organic matter dynamics. It also helps in building a basic understanding of the direct role of large herbivores in cycling of nutrients.

Climate change has a significant impact on forests and people dependent on them. High mountains around the globe are some of the most vulnerable systems and of great concern for conservation. The Himalayan mountains are experiencing a higher warming than average global warming, which can significantly impact their biodiversity, vegetation distribution and ecosystem structure. The plants growing in the Himalaya will have to adapt accordingly to survive the changing climate. Variations in climate impact tree growth and significantly influence cambial phenology and wood formation. There is a need to precisely document cambial phenology and wood formation in Himalayan trees to better understand climate-growth relationships and their response to future climate change. In this thesis, the dynamics of cambial phenology along an altitudinal range of the west Himalayan fir, Abies pindrow, was studied. Various stages of cambial phenology, duration and rate of wood formation were assessed from anatomical observations of xylem during the growing season from samples taken from three sites at various altitudes (2392-2965 m a.s.l.) over two years. In the 2nd part, climate-growth relationship along the altitudinal gradient using tree rings was investigated between monthly climate and radial tree growth from 1901-2016. The relationship was also studied using seasonal climate data. The temporal stability of this relationship was also studied to understand the impact of recent climate warming on climate-growth relationship. Finally, site chronologies from climatically sensitive trees were built and their response to regional climate was used for reconstruction purposes. The lower altitudinal site trees showed a good response to early growing season precipitation which was used to reconstruct the spring precipitation of Srinagar for last 200 years. Furthermore, growth responses to daily climate data was used to reconstruct the regional climate at a more finer scale. These findings give new insights into the dynamics of cambial phenology and climate-growth relationships and help in better understanding of potential impacts of climate change on tree growth and forest productivity in Himalayan forests.

Life on earth can be extremely complex where different parts function together for the survival and reproductive success of the organism as a whole. Evolution of complexity required several small steps known as major transitions. Among such transitions during the evolution of life, certain events are unique (for example; evolution of genetic code), whereas other transitions might have happened multiple times through the history of evolution of life on earth.

There are obvious difficulties associated with discussing rare events such as evolution of genetic code, evolution of eukaryotic cells, and origin of life. However, we have an advantage while making prediction about how life must have originated on earth. This is because our predictions about the origin of life should adhere to the well-accepted laws of chemistry and mechanisms of natural selection. Since, most living organisms contain self-sustaining chemical system- dependent on external source of energy, and properties such as heredity, reproduction and differential reproduction. It is predicted that early life on earth must have exhibited these properties. Furthermore, growing body of evidence suggests that RNA molecules must have served as a replicating molecule responsible for heredity and also for coding metabolism inside primitive cells.

For evolution of metabolism and maintenance of RNA, both template and replicase activity is needed to be enclosed in some form of a physical compartment. Additionally, compartmentalization will lead to concentration of molecules, provide protection from environmental conditions, and allow evolution of cooperative network between replicating molecules. Given the significance of compartmentalization, I will discuss how simple lipid vesicles – protocells - might have functioned as an early barrier between extracellular and intracellular environment. However, without complex machinery used by modern cells for growth and division, simple vesicle-like early cells must have exhibited properties of spontaneous duplication and growth. I will discuss how the mechanism of spontaneous duplication and growth might have resulted in competition between vesicles. Overall, in this seminar, we will review properties of the early cell-like structure that until recently was a complete black box, and how the information gained from recent empirical evidence has helped us better understand the early evolution of life on earth.

Cooperation has played a grand role in the evolution of diversity and complexity of life on our planet. Some of the most spectacular and most visible examples of cooperation are reproductive cooperation among social insects such as honeybees, division of labor in the colony of leaf-cutting ants and among cells of multicellular organisms. In all of these examples individuals within a group are highly related. Such high relatedness might be favored because it prevents conflict that might disrupt the functioning of the cooperative group. However, interactome within and between social groups of organisms that have retained reproductive autonomy and exhibit within group variations remain unknown.
Using natural social groups of Myxococcus xanthus that are internally diverse, we show that within-social-group diversity in the natural populations has positive effects on overall group productivity. This positive effect of mixing was only limited to interactions between isolates from the same social group and might be the result of overwhelmingly common bidirectional positive interaction effects between pairs of isolates. Strikingly though, mixing effects between isolates derived from different fruiting body were strongly negative. Our findings therefore provide an intuitive ecological explanation for the ease, with which possible shift in the level of selection might occur in the populations that coexist together over an evolutionary timescale.
Next, using two natural isolates of M. xanthus sampled from the same fruiting body on soil, we demonstrate that M. xanthus spore germination is a cooperative process involving production of public good molecule. Moreover, inability to germinate defect exhibited by one strain under saline stress in pure culture is socially complemented by the presence of another strain that is fully proficient at germination. Complementation confers a cheating advantage to the defective strain and is mediated by secretion of glycine betaine, an osmo-protectant utilized in all domains of life that functions as a public-good molecule necessary for germination in salty environments. These findings suggest that spore germination may be a socially multi-faceted process in other microbes as well.
Bacteria use dormancy as a bet-hedging strategy to overcome unfavourable environmental conditions. The dormant individuals such as spores or persister-cells with low metabolic activity can determine community dynamics in future generations. Although importance of social interactions has been documented among actively growing microbes, role of social interactions between individuals in diverse communities during transition to, and away from dormancy, remained unclear. Our results demonstrate importance of synergistic interactions within natural social groups of M. xanthus during conversion of actively growing cells to dormant spores and also during resuscitation of spores to actively growing cells.

Many ecosystems exhibit striking patterns in the spatial distribution of organisms, for example, patterns of clumping and dispersion in semi-arid vegetation, mussel in inter-tidal beds and even sea-grass and macroalgae. Elucidating local-scale processes that generate these macroscopic patterns is of fundamental ecological importance. In addition, these patterns may provide insights and tools to quantify stability and forecast the future dynamics of ecosystems. We now know that several ecosystems may undergo abrupt and irreversible changes in the density of their dominant communities, potentially resulting in local extinctions. Discerning the vulnerability of ecosystems to such regime shifts has become an important focal area of research in recent times. In this thesis, I investigate methods to detect vulnerability of ecosystems using high-resolution spatial data, which is becoming increasingly cheap and easily available. To do this, I use spatially explicit models of ecosystem regime shifts, inspired by simple models of state transitions in the physics literature. I also demonstrate the theoretical results with vegetation data from semi-arid ecosystems. My main findings are that some key previously proposed metrics of regime shifts when applied to high-resolution spatial data can give misleading signals and are theoretically unfounded. I argue that a clear understanding of how local interactions between organisms scale to their spatial distribution is crucial to correctly inferring ecosystem stability.

Research on intrasexual competition has largely focused on males. Competitive signalling and aggression strategies used by males have been widely studied. It is increasingly recognised that intrasexual competition may be common among females too; but our understanding about female competitive strategies is largely restricted to eusocial insects and cooperative breeding societies. Unlike males who compete to mate, females in polygynous systems rarely get large immediate fitness gains through intrasexual competition, since they are limited by the time it takes to successfully produce offspring. Additionally, because of their investment in young, the costs of overt competition, such as conspicuous signalling and physical aggression, are expected to be relatively high for females. Accordingly, females are expected to use inconspicuous broadcast displays, should be more sensitive to the perceived threat and invest in competitive signalling and aggression only when the threat of a competitor is high. We tested these hypotheses by observing P. dorsalis individuals in the wild and simulating intruder threat at multiple threat levels on their territories. Analysis revealed that females use relatively less conspicuous behaviours as broadcast displays. While both sexes increase signalling in high threat conditions as compared to low threat conditions, females show a substantially larger increase than males. Sex differences in physical aggression were also seen. Here, I discuss the implications of these sex differences in signalling and aggression in intrasexual competition in a polygynous tropical agamid.

How biodiversity is generated and maintained is a fundamental question in ecology and evolutionary biology, and studying diversification can give us key insights into this process. In my thesis, I carried out species delimitation and investigated the pattern of lineage and morphological diversification in a continental radiation of Hemidactylus geckos. The underlying role of climate in generating these patterns was also examined. Through systematic sampling and molecular phylogenetic work, evolutionary history of these geckos was traced. Fossil-calibrated phylogeny showed that Hemidactylus started diversifying ~36Mya, with an early-burst in lineage diversification. Using a hypothesis testing framework, I show that the drying caused during the Eocene-Oligocene cooling could have provided ecological opportunity driving lineage diversification. I then examined ecological diversification by studying morphological evolution. Species of Hemidactylus are found in various microhabitats and the relationship between habitat specialists and their morphology was assessed. We found significant differences in morphology between terrestrial and climbing species. Unlike lineage diversification, morphological diversification showed a delayed increase in disparity. Ancestral state reconstruction of terrestrial and climbing forms showed that the terrestrial geckos have evolved at least five times independently across the phylogeny. The shift from climbing to terrestrial state began after 15Mya, concurrent with aridification in Peninsular India that led to the establishment of open habitats. Thus, this study highlights the role of two disparate climatic events governing the asynchronous lineage and morphological diversification in this adaptive radiation.

In an age where the phrase “climate change” can no longer be ignored, we (scientists) are expected to know if and how global warming will change the world we live in. There are so many papers that predict dramatic ecological changes based on organismal responses to climatic projections; and much of those prediction are about species extinctions and range shifts. A closer look at some of these papers quickly reveal that we have forgotten our basics: the physics and physiology of thermal adaptation. I will take us quickly through a lesson in thermal biology of ectotherms and then together, we can critically look at some of the global analyses of predicted lizard extinctions (that are simply rubbish).

South Africa lies at the meeting point of two ocean systems and experiences significant clines in environmental parameters such as temperature and productivity, which in turn affect the composition and species diversity along its coastline. As such, several biogeographic regions are recognised, which differ in faunal and floral composition. My talk examines the genetic, and more recently, genomic advances that try to unravel the processes that have shaped the patterns of species diversity, particularly in South Africa, with particular emphasis on the past fifteen years. My talk provides an overview of the natural history of South Africa, its marine biogeography and the challenges, constraints and successes of our lab in sequencing species at different spatio-temporal scales and contributing towards highlighting South Africa not only as a region of exception natural interest, but also scientific excellence.