Multiple traits, including antipredator responses, foraging behaviour, development rate and fecundity, contribute towards an organism's fitness. These diverse traits interact through the shared resources allocated to maximise fitness. Ecological conditions can affect these interactions by driving increased investment in a particular trait at the cost of other traits (inter-trait trade-off). How are these interactions affected when an individual goes through different development stages, which serve different functional roles? What are the consequences for an individual's fitness in such a complex life-cycle? To understand the trade-offs that operate at multiple levels in a complex life cycle, I investigated the role of early predation risk conditions across the life cycle of the holometabolous insect– Aedes aegypti. Aedes aegypti has four major stages: egg, larva, pupa, and adult. Previous work suggests that ecological conditions experienced by the larval stage affect adult traits. However, we lack knowledge of how early larval conditions affect the pupal stage and the cumulative effects of both stages on adult traits. To understand multistage, inter-trait trade-offs, I exposed the immature stages to a key selection pressure, predation risk. Leading to our aim of understanding the combined and individual roles of larval and pupal stages in managing trade-offs, I first unravelled the relationship between larval and pupal stages. I adopted behavioural approaches to examine (1) the carryover of larval predation-risk experience on the pupal stage to understand if a pupa independently responds to risk or whether the larval experience influences its response to risk conditions. I discovered that a pupa that has experienced predation risk as a larva modulates its response to predation cues, showing that the larval experience affects pupal traits. This experiment showed that a behaviour or experience with an adaptive value can overcome the barrier of metamorphosis. Since Aedes aegypti larvae and pupae are found in group settings, I also examined (2) the behavioural manifestation of predation experience in a group setting. This allowed me to understand the abilities of the pupal stage in responding to risk conditions under different contexts. I found that experience does not influence the behaviour of an individual pupa if it is in a group. This is probably because being in a group is an antipredator response itself. My first two chapters highlight the need to include the pupal stages in life history studies because of their ability to process different cues while responding to their environment. After discovering the context-dependent antipredator response of the pupal stage, I examined (3) the multistage trade-offs, driven by early predation risk conditions, between larval-adult, pupal-adult and larval-pupal-adult stages. I performed lab-based controlled experiments where I followed all the life stages under risk and no-risk conditions. On analysing diverse morphological, biochemical and life-history traits of risk-experienced and naive individuals, I demonstrated that the fitness consequences differ for males and females, and it may start from larval-pupal trade-offs and accumulate as the risk persists. I also found that the pupal stage, like the larval stage, can respond to risk conditions both behaviourally and physiologically. However, it is less well-equipped than the larval stage to manage the trade-offs. Fitness consequences are worse when the pupal stage alone experiences risk. Hence, different stages can contribute to trade-offs that lead to various fitness consequences. My thesis yields novel insights into life history evolution by displaying the ability of individual life stages to manage trade-offs. It highlights the importance of a poorly understood pupal stage, which can respond to different environmental cues, behaviourally and physiologically. It also explains how the abilities of individual stages to manage trade-offs independently and cumulatively can change the consequences for adult fitness.

Convergent evolution of traits is a common feature across the tree-of-life. However, only certain taxonomic groups repeatedly evolve a specific suite of traits and very little is known about why this is not widespread. In ants, one such complex trait is polygyny (multiple-queen colonies) which has evolved repeatedly from an ancestral phenotype of a monogyne(single-queen colony).  Polygyny results in large supercolonies made up of unrelated workers and several behavioural, morphological, and life history modifications. I will talk about my postdoctoral work examining the genomic basis of such a trait in the desert ants from Israel, where both these traits are found in a single population. I find that differences in the number of queens is associated with the presence of a supergene, a large non-recombining region of a chromosome that codes for a complex trait, much like a sex chromosome. I then discuss how this supergene is inherited, maintained, and possibly introgressed into other lineages. Finally, we look at how conserved this region is and hypothesize about the genomic basis for repeated evolution of such traits.

Venom, being an adaptive trait, has propelled the expansion of snake lineages across diverse habitats, such as the biogeographically distinct Indian landscapes. Natural selection optimises the potency, composition and lineage-specificity of the snake venom arsenal for effective prey capture or predator deterrence. Therefore, venoms of several closely related snake species have been documented to exhibit tremendous spatial venom variation owing to their distinct evolutionary ecology. However, research on venoms in India has predominantly focused on assessing the compositional variation in certain snake species from restricted locales. These studies have also evaluated the venom variation only from a biochemical perspective without considering the ecological and evolutionary significance of such compositional differences. Hence, several questions pertaining to the evolutionary ecology of Indian snake venoms remain unanswered.

Naja naja and Daboia russelii are two medically important snake species that are widely distributed across distinct bioclimatic regions of India, including arid deserts, fertile plains, rainforests and hot-humid coasts. In addition to their clinical relevance in the snakebite scenario, these two species are fascinating model systems to understand the relationship between evolutionary ecology and venom variation. This doctoral thesis was designed to decipher the relationship between various ecological and environmental determinants and the variability in N. naja and D. russelii venoms. For this, venoms of wild-caught snakes from the major biogeographic zones across the country were sampled. A multi-faceted approach involving proteomics, biochemical analysis, pharmacological assessment and toxicity studies was employed to characterise the extent of variability. These studies revealed remarkable intraspecific variation across populations of these two species. The venoms varied significantly in terms of their composition, functional profiles and toxic potencies.

Further, the contribution of various abiotic, biotic and life history factors in dictating this variation was evaluated. A theoretical prediction model was developed to explain the variation observed in the enzymatic activities of D. russelii venom due to the combined effect of bioclimatic variables in a region. The feeding ecology is amongst the major biotic factors that drive venom evolution. Therefore, the prey-specificity of N. naja and D. russelii venoms was examined as a proxy to understand the relationship between compositional variation and diet. The venom specificity was determined through in vitro binding and in vivo lethality experiments against distinct prey organisms.

In addition to interpopulation variation, venoms were documented to vary between individuals within the same population. Therefore, the extent of intersexual and ontogenetic venom variation within a population was characterised by housing multiple clutches of these venomous snakes under captivity. The differences and similarities in the venom composition, potency and specificity across sexes and ontogenetic stages of N. naja and D. russelii individuals were recorded. While intersexual variation was not observed in either of the species, marked differences were observed between the venoms of young and adult D. russelii snakes. However, adult and juvenile stages of N. naja were found to produce functionally similar venoms. These results shed light on the influence of distinct ecologies on temporal venom variation across the developmental stages of a species.

Finally, the repercussions of venom variation at various levels on snakebite treatment in India were investigated by performing WHO-recommended preclinical studies. These studies highlighted the shortcomings of the currently employed conventional antivenom therapy in mitigating snakebites across the country. Overall, these studies also provided valuable insights for the development of advanced snakebite therapeutics that have the potential to save the lives, limbs, and livelihood of India’s thousands of annual snakebite victims.

TBD

TBD

TBD

TBD

Arid grasslands are open natural ecosystems covering 19% of Earth’s terrestrial surface. They are grazed by both wild animals and livestock. Grazing based livestock farming is the basis of rural Economy in India, especially in arid regions where agriculture is not economical. However, increasing livestock poses pressure on continuously declining grasslands decreasing native flora and fauna. Hence, my study is focused on the difference in plant community composition, plant diversity, plant traits, and soil nutrients in grazed and long-term ungrazed sites in Chitradurga, Karnataka. I hypothesize that plant diversity and soil C:N ratio will be lower in grazed sites. Plant community composition will differ between the two sites with different plant traits (taller, higher leaf area, higher leaf dry weight in ungrazed). Preliminary results show that plant richness is higher in grazed sites with no significant difference in diversity between the two conditions. Plant species composition in grazed sites were more similar than in the two ungrazed sites. I also found that some plant species differed morphologically between grazed and ungrazed sites. To unravel whether this difference was plasticity or due to evolution, and if it is adaptive, I will carry out common garden experiments followed by reciprocal transplantations. In unfavorable conditions some plants might exist only as seeds. To get a picture of the potential vegetation of the grazed and ungrazed sites, I will compare the plant composition in the soil seed banks, between the long term ungrazed and grazed sites. Because grazers are eating away plants before the reproductive period, I hypothesize that soil seed bank diversity will be lower in grazed than ungrazed sites. Finally, I will conduct a manipulative study, on the short-term effects of grazing on plant communities using grazing exclosures, or a controlled study of plant decomposition rate. Overall, this study will increase our understanding of grassland and grazing ecology in an arid system, while providing a primary database of herbaceous communities in these landscapes. It will provide knowledge about the recovery timing of degraded grazed lands under arid conditions, which is useful to policy makers and conservation biologists planning restoration and conservation programs.

TBD

TBD