An important area of interest in behavioural ecology is to understand the large diversity in traits related to reproduction and one explanation is that this diversity is adaptive and is shaped by natural selection. In wild populations, multiple selection pressures are likely to shape trait evolution. While these multiple selection pressures can manifest through different ecological or demographic conditions, these conditions themselves could vary predictably over space or time, or in an unpredictable manner, a relatively less studied form of environmental variability.

​In my thesis, I attempt to understand how oviposition site selection, a behaviour where multiple selection pressure regimes are rarely considered, is shaped by multiple factors in a variable environment. Using Aedes aegypti and Ae. vexans as model systems, I first measured fitness trade-offs associated with larval predation risk and conspecific competition risk at potential oviposition sites through experimental manipulation in the laboratory. I also quantified spatial and temporal variation in two risk factors, pool desiccation risk and larval predation risk, through an observational study under natural conditions. Considering these trade-offs, I predicted and tested female oviposition site selection response to these varying multiple risk factors in the field. My findings indicate that oviposition site selection responses are complex, sensitive to interactions between multiple risk factors and influenced by patterns in variability in some of these factors.

As a visiting doctoral student at IISc (2010-14) , I and my collaborators had two major streams of research. First, we attempted to understand whether elephants were functionally unique or redundant as seed dispersers in Buxa Tiger Reserve, testing the ecological theory and intuition that physiologically and behaviorally distinct species are also functionally non-redundant. Realizing that human activities near Buxa had drastically altered the forest's seed dispersal ecology, I began wondering how ecological communities might be restored in a way that is fair to local human communities. I conducted research on how purportedly voluntary village relocation from Melghat Tiger Reserve had affected socioeconomic outcomes for relocated and non-relocated villagers. After reviewing the main results from these efforts, I will explain how I hope to combine functional ecological and socioeconomic inquiry to understand how conservation interventions affect both people and ecological processes.

Structured Decision Modelling: Making Science-Based Conservation Decisions

It is becoming increasingly recognised that we need structured approaches to scientifically and transparently make conservation decisions. I will talk about Adaptive Resource Management, and Structured Decision Modelling, two linked approaches that simultaneously achieve a dual objective. First, it uses scientific information and understanding to direct conservation decisions, and second, it treats conservation decisions as natural 'experiments' to further our scientific understanding of species population dynamics. I will explain the process involved in implementing Adaptive Resource Management, in the particular context of waterfowl management. I will show how science was used to decide on hunting regulations, while simultaneously, monitoring of waterfowl allowed us to understand the impacts of hunting on waterfowl population dynamics. I will also talk to different forms of uncertainty in conservation decision-making and provide examples for each type of uncertainty. Using an illustrative example, I will then describe how Stochastic Decision Modelling uses science to direct conservation decisions. I will explain the utility function, and how it can be modified to consider future benefits, in addition to current benefits. I will cite an example of the use of Structured Decision Modelling to decide on tourism regulations in Denali National Park, such that impacts on the golden eagle Aquila chrysaetos are minimal. I will conclude by detailing the utility of such a framework for conservation contexts of India.

Species Dispersal and Connectivity in Conservation Landscapes

Resources and risk for species are heterogeneous across space, more so than ever today because of a pervasive human footprint. How do animals perceive and move through risky, heterogeneous lands to access resources and mates? What are the implications of animal movement decisions for successful establishment of linkages among populations and habitats in increasingly human-dominated landscapes? I will delve into these important questions by first looking at why we need to think about dispersal, and reviewing existing evidence across taxa that highlights multiple detrimental impacts of the loss of connectivity to species and communities. I will then discuss limits to successful dispersal in heterogeneous landscapes, placed within a framework that allows us to both question where animals move, as well as why they choose certain areas to move through while avoiding others. In many contexts, dispersal only becomes effective on successful reproduction of dispersers; by extension, factors limiting post-dispersal reproduction also impact effective dispersal or connectivity. I will show that mate choice, in the form of preference or avoidance of dispersers as compared to residents, can bring about connectivity patterns that we often see in real-world landscapes. Further, under certain conditions, impacts of mate choice can override those brought about by movement limitations. In many conservation landscapes, dispersers often move through risky lands where they frequently interact, and may come into conflict, with people. I will present findings on the implications for this perception of risk on connectivity for the Asian elephant Elephas maximus. I do so through a novel adaptation of the occupancy modelling framework such that we can now explicitly model matrix impacts on the probability of successful dispersal of elephants, while accounting for our inability to perfectly detect infrequent dispersal events. Certain strategies aimed at mitigating conflict can also increase perceived risk from humans, thus impeding connectivity and reducing long-term viability of species. I will present ongoing efforts that aim to scientifically implement conservation strategies to facilitate connectivity, while minimizing conflict for species such as the Asian elephant. I will conclude by reiterating the implications of scientific inference on connectivity for both ecology and conservation.

In tropical forests, large frugivores are assumed to be important seed dispersers for many large-seeded trees such as Aglaia (Meliaceae), a widespread and common genus. We investigated the seed dispersal of Aglaia spectabilis, a large-seeded tree species in a moist evergreen forest of Khao Yai National Park in Thailand. In quantitative aspects of seed dispesal, we assessed both the frugivore assemblages foraging on arillate seeds of Aglaia spectabilis and dispersing them and the seed predator assemblages, thereby covering dispersal as well as the post-dispersal aspects such as seed predation. The results showed that frugivores dispersing seeds were a rather limited set of four hornbill and one imperial pigeon species, whereas two squirrel species were not dispersers, but dropped the seeds on the ground. In qualitative aspects of seed dispersal, we combined data from feeding trials, germination tests, and radio-telemetry of hornbills and estimated the seed dispersal distance. We also marked all the individuals of Aglaia spectabilis within 4-ha and followed their survivorships for a period of 15 years. Hornbill gut passage had a positive effect on the germination rate of Aglaia spectabilis and were capable of dispersing seeds over several kilometers. Some seedlings of Aglaia spectabilis were distributed far from the fruiting trees and survival of 1-yr seedlings after 15 years was relatively high (16%). Heavy seed predation by mammals around fruiting trees together with high seed removal rates, short visiting times, relatively long seed dispersal distance, and regurgitation of intact seeds by mainly hornbills lead us to the conclusion that hornbills show high effectiveness in dispersal of this large-seeded tree species.

Division of labour plays a very important role in social insects and could either be reproductive or non-reproductive in nature. The lack of morphological differences among individuals in primitively eusocial species lead to greater flexibility in their social roles making them very interesting model systems to study division of labour. Ropalidia cyathiformis, a primitively eusocial wasp was chosen as the model system for the study of reproductive and non-reproductive division of labour. One of the key findings reveals that while dominance behaviour is used as a mechanism for reproductive division of labour, age is used for non-reproductive division of labour. We also compared our findings with what is already known in a related conspecific, Ropalidia marginata. Our findings showed that R. cyathiformis maybe a more primitive species compared to R. marginata and provide a glimpse into the origin of eusocial insects.

Reproduction is the avenue for gaining direct fitness. But in certain
species some individuals do not reproduce to gain direct fitness, instead
gain indirect fitness by helping relatives to reproduce; the prime
examples for this come from the worker caste of social insects like ants,
bees and wasps. Indirect fitness has been in focus for explaining the
evolution of workers while overlooking the fact that workers can also gain
direct fitness. One of the avenues for gaining direct fitness by workers
is nest foundation and I have studied this phenomenon in a social wasp. I
found that workers prepare in several ways for nest foundation, like
enhancing nutrient reserve and engaging in dominant interactions, even
before leaving their natal nests. While investigating the emergence of
cooperation and division of labour in newly founded nests, I observed how
these affect the productivities of the new nests. Finally I found that it
is ageing and nutrition and not work done towards gaining indirect fitness
that affect workers’ potential of gaining future direct fitness by
independent reproduction.

It is often believed the ecological and evolutionary timescales are very different and that it is difficult to study ecological and evolutionary processes together in a
rigorous and controlled manner. However as the experience of the last few decades shows, experimental ecology and evolution studies in laboratory settings provide us with
the ability to rigorously examine such phenomena and test hypotheses about evolutionary and ecological mechanisms, and their interactions, in a manner that is not possible
in the wild. In this talk, I will discuss a few examples from work in my laboratory over the past twenty years to illustrate the power of this approach, and underscore the
point that the evolutionary process is far more subtle and responsive to minor changes in ecology than is often thought to be the case.

TBA

Tropical habitats face a number of threats as a result of human activities. Two common and important anthropogenic threats to tropical biodiversity are invasive species and roads. Roads can have negative ecological consequences by degrading and fragmenting habitat, causing edge-effects, and increasing the risk of road-related mortality, hunting, fire and spread of invasive species. Lantana camara (henceforth lantana), a widespread invasive plant, can form dense monoculture thickets covering large areas, and yet knowledge is rare about its impacts on higher trophic levels, especially insects. I studied impacts of these two important proximate drivers of habitat disturbance, namely lantana and roads, on habitat use by butterflies in a tropical moist deciduous forest in Western Ghats of India. Both are expected to modify micro-habitat structure, resources, micro-climate and other aspects of the ecology of butterflies and thereby influence how they use space (i.e., micro-habitats within the larger habitat). Because systematic ecological information on tropical butterflies is comparatively limited, I adopted a multi-species approach. I examined habitat use responses of butterflies to a gradient in lantana cover within the forest, and to an unpaved road passing through the forest. The abundance of a butterfly species in different micro-habitats was taken as a measure of its habitat use. Data was collected over two seasons and at two spatial scales. Road and lantana were found to influence habitat use by butterflies. While there was substantial difference in the kinds of butterflies encountered on the road vs. the forest interior, high lantana areas in the interior appeared to contain only a subset of species encountered in low lantana areas. At a smaller spatial scale, a different set of species was encountered on lantana plots as compared to non-lantana plots. I then correlated the responses of butterfly species to road and lantana with their functional traits, as a way to detect general patterns. For this, I built a traits’ database by measuring morphological traits in 254 butterfly species from India and classifying them according to their habitat preferences (based on expert opinion). I examined relationships between morphological traits, habitat preference and evolutionary relatedness in butterflies. I then examined patterns of correlation between these traits and responses to the two habitat disturbances and found that certain traits can help predict response.
To summarize, my study suggests that butterfly habitat use is influenced by forest disturbance due to roads and lantana, though the response varies across species. Species with
certain traits may be especially vulnerable to these disturbances. The behavioural habitat use responses observed in my study can have population or community-level consequences that need to be further examined.