The India-Asia collision in the early Tertiary and the subsequent climatic and geographic shifts had profound effect in shaping the biotic community on both the landmasses. However, the impact of such abiotic factors on freshwater invertebrates is not well understood. Freshwater snail family Viviparidae is known to have colonized India from Southeast Asia, but knowledge on the temporal pattern of these dispersals is lacking. Understanding these patterns will help us elucidate the role of climatic fluctuations and geographic changes in shaping the biogeography of freshwater organisms across the India-Southeast Asia interface. To this end, samples of all the described species of Viviparid snails were collected across the Indian subcontinent and multiple molecular markers were sequenced. Phylogenetic analysis, molecular dating, and ancestral area reconstruction were carried out with a dataset consisting of the Indian species and major Southeast Asian Viviparid genera. Preliminary results suggest independent colonization of the Indian subcontinent by two distinct lineages of viviparid snails. Furthermore, contrary to our expectations, one of the two lineages seems to have dispersed after the late Miocene aridification intensified in Peninsular India. A clearer picture will soon emerge following further analysis. Comparative studies on the ability of the two lineages to withstand aridity might provide insight into this intriguing pattern.

Why are there only 2 sexes? Why are sperm much smaller than eggs in most sexually reproducing organisms? In this talk, I will review the literature on the evolution of anisogamy. Theories for the evolution of anisogamy can be broadly divided into three categories-- those that emphasize the conflict between the sperm and egg strategies (and regard sperm as parasites), ones that emphasize the mechanisms of contact between eggs and sperm, and ones that stress on a uniparental inheritance of cytoplasmic DNA. Tests of these theories are often carried out on data from colonial green algal species, which show a range from isogamy to anisogamy.

TBA

Evolution is essentially quantitative and can be understood best via mathematical theories. But few courses or even text books cover basics of evolution in a quantitative way. In this context, I will introduce Price equation in an intuitive way. Its simple, elegant and easy to make sense of. I argue that basic evolutionary biology courses teach principles of evolution using Price Equation, which has a prerequisite of no more than an understanding of mean, variance, slope and correlation.

For most of the animals, if not all, finding their way to a particular place is crucial for survival. To address this challenge of way-finding, different animals have evolved with different homing strategies. Social hymenopterans like honey bees, ants and wasps are of special interest – foragers of these insects show excellent homing capabilities while having simple neural resources. In this study field, honey bees and ants (desert ants, in particular) are among the most studied animals. Compared to these insects, our understanding on the homing mechanisms of social wasp is rather poor. For my thesis, I have studied homing behaviour of the tropical social wasp Ropalidia marginata, a predator in their foraging habit. To begin with, first I had to know their typical foraging range, which I found to be within about 500 m from their nest. Forager wasps possess a surprisingly well-developed familiarity with their foraging landscape, apparently more intricate than honey bees and desert ants. They acquire this spatial familiarity through flying around the landscape before starting foraging for food. Compared to honey bees and desert ants, this learning period in wasps appears to be much longer – this can be attributed to the much higher density of the tropical landscape in which they have evolved. I have also found that, if needed, they can fly to a distance of about 1.5 km for foraging and can return to their nest even if passively displaced to familiar and unfamiliar places. To return from unfamiliar places, they probably use some sort of searching mechanisms – a skill that they improve with their age. Such searching behaviour is prevalent throughout other hymenopteran insects. I conclude that capability and mechanisms of spatial orientation, navigation and homing in animals are much influenced by their evolutionary origin and the environment in which they have evolved.

An important area of interest in behavioural ecology is to understand the large variation in traits related to reproduction and one explanation is that this variation is adaptive and is shaped by natural selection. In wild populations, multiple selection pressures are likely to simultaneously 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* as a model system, 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.

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.

Many organisms (including humans) depend on sound for communication, predator/prey detection, and navigation. Thus, the intrusion of anthropogenic noise has consequences, masking natural sounds, altering wildlife behavior, physiology, and distribution and increasing stress and annoyance in humans. My research focuses on the science of sound in a landscape, examining the distribution and impact of noise pollution and monitoring biodiversity using acoustic recordings. Using thousands of hours of acoustic recordings and continental-scale sound models I examined the level and drivers of noise in U.S. protected areas. I found that noise pollution was pervasive, doubling background sound levels in 63% of U.S. protected area units and causing a ten-fold or greater increase in 21%, surpassing levels known to interfere with human visitor experience and disrupt wildlife. The dominant noise sources were aircraft and automobiles, while the loudest noises were emitted from trains and watercraft. Using a spatial planning approach, I am working to combine this information to build a framework for a national noise mitigation strategy. Extracting meaningful biological information from large-scale acoustic recordings can be problematic given the volume of data, with many approaches being prohibitively labor intensive and time consuming. Thus, I test the utility of bioacoustics indices, which are increasingly used to rapidly characterize biological communities. I reviewed the acoustic index literature, analyzing the efficacy of different indices to characterize bioacoustic activity, species richness, functional diversity, and landscape attributes. I then implemented a subset of the most effective indices on acoustic data collected at over 50 sites in both terrestrial and aquatic habitats across the continental U.S. I found that bioacoustics indices reflect the richness of species vocalizing in acoustic recordings and the abundance of common avian species song. Thus, bioacoustics indices and large-scale recordings offer a powerful tool, with the potential to monitor the dynamics of biodiversity and ecological communities across enormous spatial-temporal scales.

The Western Ghats is a biodiversity hotspot extending along the west coast
of India. It has a high endemism and harbours over 5000 plant species.
Whereas, the evergreen forests populating the wet zone on the western
slopes have existed since 65 million years ago, the deciduous forests
populating the eastern plateau were established during the Miocene
aridification about 10 million years ago. Additionally, the wet zone also
has a latitudinal gradient in length of dry period that was established
after the intensification of the monsoons and thus affects species
composition, with the relict evergreen species largely confined to the
southern refuge pocket. In this study, we tested the antiquity of the
evergreen forests, the southern refuge hypothesis, and the relationship of
species across these forest types.

We found evergreen forests show antiquity compared to deciduous forests,
and PD patterns corroborates the southern refuge hypothesis. Most
interestingly, deciduous forest species show shared evolutionary histories
with evergreen forest species, suggesting shifts in this trait, whereas
evergreen forests show greater disparate histories possibly due to their
antiquity and sharper gradients in the wet zone.