The evolution of flamboyant traits in animals is typically attributed to the selective force of sexual selection. However, natural selection can constrain the degree of elaboration of such traits. Therefore, animal signals reflect a balance between natural and sexual selection. I examined the role of these forces in the maintenance of a complex visual signal: dynamic colour change. Males of the Indian rock agama (*Psammophilus dorsalis*) exhibit rapid dynamic colour changes on their dorsal and lateral body regions during social interactions. The costs, benefits and adaptive significance of this relatively rare signal type is yet unknown.

Using a combination of visual modelling and field experiments, I first examined the predation risk on social colours and found that the courtship signal of males is costlier than the aggression signal. I then tested whether male colours expressed during aggression convey information about individual physiology and performance measures. Apart from a negative association between testosterone levels and the yellow colour expressed during aggression, body size and bite force were correlated, suggesting that body size could be an honest predictor of fighting ability. In the third chapter, I examined differences in health parameters of males and females that occupy dramatically different habitats as a consequence of urbanization. Our results suggest that lizards in urban areas appear to have shifted their innate physiology in order to cope with urban stressors. Finally, I examined the response of receivers to different components of the male colour signals by assessing attention paid by conspecific receivers to each signal component independently and together. Both males and females responded equally to all male social colours although females showed difference in response to achromatic signals. Overall, we conclude that dynamic colour change may have evolved in this species to actively balance the costs of predation risk with the benefits of social signalling.

The Western Ghats (WG) is one of the major global biodiversity hotspots, harbouring a rich diversity of flora and fauna many of which are endemic to the WG. The current understanding of the biogeographic history of WG comes from paleo-floral records and taxonomic diversity studies, but hasn’t been explored from a phylogenetic perspective. This was the inception of my study with the main aim to understand the imprints of biogeographic history on the phylogenetic diversity (PD) of the flora of Western Ghats. I first studied the PD patterns of local deciduous forest patches (Nandi Hills, Savandurga, and Devrayanadurga) to evaluate the usefulness of PD in the Indian context. Whereas other studies have shown that PD can be decoupled from taxon richness in biodiversity hotspots, my results showed this decoupling even in regions of low diversity. I then used these tools of community phylogenetics to analyze the patterns of PD across the WG. My premise was that if the deciduous forests of the WG are indeed more recently established than the evergreen forests (as literature suggests), then evergreen PD would be high and deciduous PD would be low. My results indeed show this pattern, corroborating this hypothesis. Within the evergreen belt, I found PD patterns that corroborate the southern refuge hypothesis, with higher PD in south compared to north. I also analyzed the phylogenetic turnover between these forests and showed that whereas the deciduous and evergreen taxa have shared evolutionary histories, the evergreen taxa from different forest types have quite disparate evolutionary histories. Phylogenetic endemism (PE) analysis (analyzing ranges of clades rather than taxa) showed that most paleoendemic plots are found south of 12-degree latitude indicative of refugial regions as postulated by the southern refuge hypothesis. Toward the north and south are clusters of neo- and paleo- endemism, which indicate that clades are restricted in distribution mostly in south, but also in north, with the central WG being a region of overlap of these ranges. My study is the first to provide a phylogenetic perspective toward understanding the biogeographic history of Western Ghats. It provides a fresh line of evidence corroborating current hypotheses and uncovered many interesting patterns which need further exploration, integrating tools from both community ecology and biogeography.

Dispersal has important ecological and evolutionary consequences for a species. Marine dispersal is unique because of facilitation by ocean currents, where oceanography interacts with species traits and environmental heterogeneity to determine connectivity between populations. However, marine dispersal research has largely focused on coral reefs and temperate shores, while tropical coastlines remain poorly studied. To address this gap in knowledge, we studied dispersal patterns and processes along the Indian coastline using two genera of intertidal littorinid snails (Littoraria and Echinolittorina) as a model system. We used a comparative framework to study the influence of species traits on patterns of mitochondrial phylogeography and deduced environmental correlates of range using species distribution models. We also performed larval dispersal simulations to derive estimates of coastal connectivity.
We found that all species showed signatures of demographic expansion in the Pleistocene, and only two species with wide environmental tolerance showed population genetic structure. Gradients in sea surface salinity and tidal range along the coastline were important in predicting distribution patterns across species and scales. There were seasonal differences in oceanic connectivity patterns, where certain sections remained isolated from the rest of the coastline. Regions predicted to have poor connectivity overlapped with observed species turnover for a range of marine taxa. These multiple lines of evidence suggest that variation in environment and oceanographic connectivity can influence dispersal patterns along tropical coastlines. This study presents hypotheses related to species-environment relationships and population genetic connectivity, which can be tested in other taxa to arrive at a unified framework of coastal biogeography for this region.

In the tree cricket, Oecanthus henryi, males invest in long-distance acoustic signals which the females use to identify and localize conspecific mates. Males that live and call longer or louder are expected to have higher mate attraction opportunities. O. henryi males with softer calls also exhibit an alternate signalling strategy called baffling. Baffling increases the sound pressure level (SPL) of the signal by 8-12 dB, thereby increasing their mate attraction potential. Interestingly, most call features in O. henryi, including SPL, show a low across-night repeatability, indicating immediate condition-dependence. Nutrition and age can contribute to immediate male-condition. Therefore, in this study we investigated the effect of diet on male longevity and the interaction of diet and age in determining lifetime male calling propensity & calling duration in a semi-natural set-up. In concordance with our expectation, males on high-nutrition lived longer, had a higher lifetime signalling and had longer within-night calling duration. We, moreover, studied diet-dependent phenotypic senescence of male acoustic signals. Males on high dietary-condition sustained their high signaling activity while males on poor dietary-condition suffered a sharp decline in signaling. We also examined how nutrition & age affect non-baffling SPL and consequently, baffling behaviour. We hypothesized males on poor diet-condition to have lower non-baffling SPL and hence, higher baffling probability. We also expected to find similar pattern of age-dependent decline in non-baffling SPL and consequent increase in baffling probability. We, however, did not find any effect of diet and age on signal SPL and baffling probability.

How does our brain enable us to pay attention selectively to important events in the world and ignore irrelevant events? While neuroscientists have largely studied how evolutionarily newer "forebrain" regions (e.g. neocortex) contribute to attention, comparatively little is known about how evolutionarily older "midbrain" regions control attention.

In this talk, I will describe our recent work seeking to understand the role of the superior colliculus (SC) -- an evolutionarily conserved midbrain structure -- in attention. The SC can be found in all vertebrates -- from fish to mammals -- and is known to be involved in controlling eye movements in all of these species. I will describe recent experiments in birds, monkeys and humans that show that the SC is also involved in controlling attention. Specifically our experiments show that the SC controls a particular component of attention called "spatial choice bias". Understanding how the SC controls attention will be critical for understanding how evolutionarily conserved mechanisms of attention operate in the brain.

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.

Google Earth Engine

Agriculture is critical to feeding a growing global population and to supporting the majority of the global extreme poor. At the same time, it is highly vulnerable to increasing environmental stress, be it in the form of increasing temperatures or water scarcity, and a major source of pollution, ecological degradation, habitat loss and GHG emissions.

Around the world, a variety of approaches are being promoted to achieve a more ecologically sustainable agriculture, some of which emphasise modern technologies while others call for a return to more traditional forms of cultivation. Unfortunately, the debate between these different approaches often remains more ideological than evidence-based, and policy often remains disturbingly un-informed.

I will attempt to cover some of the big questions on the issue, and appeal for faculty and students to play a more active role in addressing the challenge through a rigorous multidisciplinary approach that combines the life sciences, the physical sciences and the social sciences, and is intensively field based. I will focus on the potential and specific practical opportunities for collaborations between Israeli and Indian academia, two countries suffering from various forms of environmental stress that together, I will argue, can offer a new model of applied, impactful research on the topic.

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 marine 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 my thesis, I investigate methods to detect the vulnerability of ecosystems using high-resolution spatial data, which is becoming increasingly easy to procure. 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 infer ecosystem stability.