Participation by Registration only

Participation by Registration only

Participation by Registration only

The Sterile Insect Technique (SIT) consists of the mass-production, sterilization and release of target pest insects in an affected area. Once released, sterile males mate with wild females rendering them infertile. The effectiveness of SIT depends on sterile males performing both pre-copulatory and post-copulatory behaviours in order to compete with wild males. In SIT controlled Tephritid flies, attention has been focused on pre-copulatory behaviours with relatively fewer studies on post-copulatory behaviours such as sperm transfer and the ability of males to inhibit females from remating. Here I review ejaculate dynamics in tephritid flies of economic importance, and focus on the factors that can modulate post-copulatory mating behavior.

Cooperation is ubiquitous across taxa in the animal kingdom. For example,
microbes cooperate in producing antibiotic-resistant biofilms, mammals and
birds collectively mob predators, and humans cooperate in utilization of
common resources. However, cooperation is a paradox: why does natural
selection favour a costly behaviour? One of the key mechanisms of
cooperation is a spatial structure with local clustering of cooperators
(and defectors). This exposes defectors to the consequences of their own
selfish behaviour, keeping them in check. However, a vast fraction of
cooperative species is mobile. Movement allows defectors to escape their
fate, destroying spatial structure and hindering cooperation. Therefore,
cooperation is typically thought to be difficult to evolve in mobile
organisms. In this thesis, we question this assumption, and using
simulation and analytical studies, show that coevolutionary mechanisms can
promote cooperation in mobile populations.

Species across taxa, ranging from cells and microbes to fish, birds and
ungulates, live in highly mobile groups that frequently merge and split,
called fission fusion groups. The dynamics of these groups is governed by
local cohesive interactions between individuals. In the first chapter,
using explicit spatial agent-based evolutionary simulations, we explore
the coevolution of cooperation and local cohesive tendencies as a possible
route to cooperation. We show that, mobility facilitates spatial
structuring of cooperators via a dynamically evolving difference in the
cohesive tendencies of cooperators and defectors. We use the ideas of
assortment (where cooperators interact more frequently with other
cooperators) and multilevel selection (where selection for cooperation
between groups outweighs selection against them within groups) to
understand the coevolutionary dynamics. We discover an interplay among
cooperation and grouping, where self-assorted groups favour cooperation,
and cooperative interactions in turn favour such groups. Our results
reveal the possibility of cooperation in fission-fusion populations that
are typically thought to inhibit cooperation.

In the second and third chapters, we generalize our coevolutionary model
by considering a generic coevolving phenotypic trait (or ‘tag’) that
mediates interactions. Evolution happens via two key processes: selection
and drift. Unlike typical models of evolution that often employ only one
of these, we develop an analytical model that combines both. Our model
employs techniques from statistical physics to derive coupled
Fokker-Planck and Langevin equations for a finite population of organisms.
Our main finding is that mutations and demographic noise can facilitate
the evolution of tag-based cooperation. Our results could provide insights
into cooperation among metastatic cancer cells, quorum sensing bacteria,
and early multicellular clusters.

In the final chapter, we study the coevolution of cooperation and mobility
itself, in the context of human cooperation. Humans cooperate in the
utilization of spatial ecological public goods, such as forest produce,
fisheries, and grazing lands. However, humans evolve their strategies via
social learning, by imitating more successful individuals. Here, apart
from mobility, space introduces other features like incomplete information
and eco-evolutionary feedbacks. We incorporate these features into a
minimal, agent-based, evolutionary model to study human harvesting and
dispersal strategies. We show that, as resource utility increases and
dispersal becomes cheaper, societies progress from a sedentary,
subsistence-oriented lifestyle, through a nomadic phase characterized by
efficient and equitable resource harvest, to eventual social
stratification and overexploitation of the resource. Our model can
qualitatively reproduce harvesting and dispersal patterns observed across
the world throughout human history, such as in equestrian cultures and
shifting cultivation. It also helps us develop policy insights on the
sustainability of global commons, such as timber and fisheries.

In conclusion, we investigated coevolutionary dynamics across a spectrum
of mobility (from highly mobile to almost sedentary populations), and
found that coevolutionary mechanisms can facilitate cooperation in mobile
organisms. In the process, we also obtained insights into the role of
other factors, such as demographic stochasticity, rapid evolution,
incomplete information and eco-evolutionary feedbacks, on spatial
evolutionary dynamics.

Organisms can cope with novel challenges by modifying their behaviour, physiology,
morphology and cognition. In today’s world, however, anthropogenic activities, such
as urbanisation, rapidly and dramatically change natural environments, altering
habitats as well as shifting resources and predator communities. To understand the
impacts of urbanisation on phenotypic traits, I studied the social and survival
strategies of the Indian rock agama, Psammophilus dorsalis. Using a combination of
field and laboratory-based experiments, I examined differences in gross morphology,
signal-receiver dynamics in communication, anti-predator strategies, stress
physiology, and spatial learning. Social interactions in this species involve rapid
physiological colour changes and behavioural displays. My work shows that colour
patterns are diametrically different between courtship and aggressive interactions;
and that urban males express lower colour contrast and were slower to change colours
than rural males. Using robotic lizard stimuli, I found that receiver responses
match population-specific intensity of male signals. Escape strategies of males, but
not females, also differed between urban and rural populations, such that urban
males were more tolerant of simulated predator attacks than rural males. As expected
from their cryptic body patterns, females regardless of habitat, relied more heavily
on crypticity rather than flight to minimize predation risk. Urban males also had
stronger cognitive skills, as spatial learning and reversal learning was faster than
in rural males. Along with these phenotypic shifts, stress physiology was also
affected, as urban males had significantly higher circulating corticosterone levels
than rural males. In sum, differences in these phenotypic traits between urban and
rural populations suggest human-induced changes in selective pressures that support
shifted survival and reproductive strategies.

The Asian Horned Frogs (Megophryinae: Megophryidae) are a taxonomically and systematically poorly known group of primarily montane specialist species. They are found throughout the southern Himalayas, central and southern China, Indochina, the Greater Sundas and the Philippines. I will present part of my PhD thesis work that aimed for the first time to elucidate the phylogenetic relationships and evolutionary history of Asian horned frogs based on the most taxonomically complete study of this group ever to have been attempted. Beside determining how species (and species groups) are related to each other, I will discuss how we overcame the problems of estimating ancestral divergence ages given the absence of a fossil record for this group, and the surprising results that might lead to a re-evaluation of divergence dates of other frog families. My work required a complete overhaul of horned frogs taxonomy, synonymising genera and identifying many currently unnamed ("new") species that have previously been hidden under "catch all" cryptic species complexes.

Smallholder agriculture will need to become much more efficient and precise in its use of water, energy, and chemical inputs if it is to become environmentally sustainable. However, diffusing efficient cultivation technologies among smallholders faces many social and economic challenges, requiring innovative solutions. I will describe some example and experiences from related field work in India around attempts to reduce water and nitrogen use, and opportunities for students to become involved in such research.
I will focus on emerging opportunities for Indian-Israeli collaboration in such research, including a summer program in Tel Aviv university that offers scholarships to selected Indian students.

Understanding how plant communities have been structured by past environments, and predicting how they might respond to future environmental changes, requires an understanding of plant strategies with respect to resource use, climate and disturbances. Functional traits are measurable morphological and physiological metrics that can be used to draw inferences about these underlying strategies.

In this presentation, I draw on examples from savanna-forest transitions across the globe to consider how the functional traits of tropical savanna and forest plants are indicative of growth and survival strategies that are shaped by their distinctive environments. I present some recent data on plant traits and disturbance regimes from some Indian savanna-forest transitions to contextualize these ecosystems in this comparative framework. I conclude with some unanswered and puzzling questions in these ecosystems.

The Iron Age-Early Historic burials, more popularly known as megalithic burials, attracted attention of archaeologists, historian and general public alike. These burials, often identifiable by certain patterns of arrangements of usually larger stones on the surface (hence termed megalith), are found across the landscapes in the five southern states of India. They are dated, through various methods, from as early as 2000 BCE to as recent as 600CE. The practice of raising these burials was associated with the beginning of Iron Age, following the Neolithic period in peninsular India.
My research primarily focuses on understanding the material culture of people of this period thorough examining these burials. The patterns of these burials with occasional discovery of artifacts provide us with a range of understanding not only about the cultural traditions of the period, but also about the nature of variation both within a site and across sites in landscapes. Drawing examples and inferences from my field research and excavation in a site in north Tamilnadu, I would reflect upon some of these questions in the talk. These burials have fascinated archaeologists for over 200 years due to their visibility on the landscape, but the questions regarding these burials remain numerous as it was centuries ago.