A one day symposium on Animal Signals: Functions and Evolution to be held on Thursday, 12th December, at CES, IISc. Prof. Marlene Zuk from University of Minnesota will be delivering the opening talk.

Sexual selection has long been known as the force underlying the evolution of male ornaments and armaments that males use to gain access to mates. However, what is less understood is what happens when females mate with multiple males, causing sperm of different males to compete for fertilization. Selection for sperm that are both more competitive and better able to overcome the challenges of the female reproductive tract has brought about tremendous variation in sperm size and shape. I will discuss recent comparative work on the causes and consequences of variation in sperm form and function, including the evolution of the longest sperm ever measured. I will further discuss how males trade off the allocation of their limited resources between producing copious high-quality sperm and the costly ornaments and armaments to gain mating opportunities in the first place.

From a million giant wildebeest crossing political borders in the Serengeti to a minuscule bacterial colony moving across an agar gel in a petri-plate, migratory behaviour can be seen at all scales. Migration has evolved multiple times independently in many animal groups, such as birds, fish, mammals (including marine mammals and bats), reptiles (e.g. sea turtles), amphibians, insects and marine invertebrates. Although the evolution of migration in most cases is a response to seasonal fluctuations, its occurrence and extent depends on many physical, geographical, historical, and ecological factors which are likely to facilitate and/or constrain the evolution of migration. My thesis work broadly revolves around understanding the pattern of evolution of migration in birds. I use a meta data analysis approach to estimate global patterns in evolutionary history using ancestral character state reconstruction.

In my study, we target two aspects of migration: Group migration (where individuals of a species migrate together in groups) and Long-distance migration. In the chapter where we focus on Group migration, I test the idea that the evolution of group formation in ecological contexts other than migration may facilitate the evolution of migration in groups. In the other chapter where the focus is on Long-distance migration, we are trying to understand the plausible evolutionary trade-offs between the costs of elaborated traits and costs of long-distance journey. Before carrying out these two sets of comparative analyses, I have also carried out simulations to test for the efficiency of the phylogenetic method that I use in my study. I will briefly discuss the results of those simulations and will focus mainly on the work on group migration in this presentation.

Animals across taxa and habitats are known to use available space nonrandomly.

They are known to concentrate their space use around locations rich

in food, mates or refuges. There could also be cascading effects of such

disproportionate use for the individual itself, its conspecifics or even the

landscape it inhabits. In addition to using their habitats non-randomly for

foraging, avoiding predators and optimizing homing routes; some social insects

were also discovered to use their nest space non-randomly. We tested if the

primitively eusocial paper wasp Ropalidia marginata used its nest space nonrandomly

and indeed found a majority of individuals using parts of the nest

more intensively than expected by chance (spatial fidelity). We tested several

hypotheses that were primarily based on studies on ants, to understand the

relationship between the social and spatial organization of individuals in social

insect colonies. We found that the non-random space use by adults within R.

marginata nests is a result of maximizing nutritional exchange and minimizing

disease spread in the densely populated colonies. In addition, in order to

understand the role of non-random space use by adults on task performance, we

tracked individuals while they performed the task of food distribution, as it is the

most conspicuous and important task in social insect colonies. We found that

wasps within a feeding bout cooperatively (and often repeatedly) fed the

randomly distributed larvae, thus minimizing the chances of any larvae going

hungry. Each wasp that fed larvae in a feeding bout optimized its feeding route

by minimizing the distance per unit larvae it fed. We conclude that

understanding the spatial organization of adults might help us better understand

the mechanism of efficient division of labour on social insect nests.

The Indian subcontinent has been exposed to radical geological and climatic variations over geological time. Contact with other major landmasses, and the dispersal events that resulted from them, have made India and the rest of South Asia a fascinating natural laboratory for biogeography.

Snakes constitute ideal model systems for biogeographic studies given their almost cosmopolitan distribution, the ecological influence they wield, and their evolutionary age. Snakes of the Family Homalopsidae are of special interest given their semi-aquatic habits, and the behavioural and morphological adaptations unique to this clade. Homalopsids exhibit stark differences in their distributions, abundances, and feeding ecologies. This makes them ideal for addressing questions pertaining to phylogeography, ecology, and subsequently biogeography.

I aim to study the ecological and evolutionary determinants of homalopsid distribution. First, I aim to unravel the location of origin of this family and the ancestral state (fossorial/terrestrial, or aquatic) of the crown group. This will serve as a precursor to addressing questions on how homalopsids dispersed and colonized the Indian subcontinent. I will then utilize comparative phylogeography of select species to estimate how population structure varies as a function of tolerances of these snakes to abiotic factors. This would provide insights into factors that have allowed this clade to colonize their range given the geology and paleoclimate of the Indian plate and South-East Asia. Finally, I propose to utilize species distribution models to elucidate how these and other semi-aquatic snakes respond to gradients of abiotic stressors as well as their response to other sympatric snakes.

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.

Thesis Proposal Presentation

Thesis Proposal Presentation

Thesis Progress Presentation

Thesis Proposal Presentation