Alternative reproductive tactics (ARTs) are discrete phenotypes employed by individuals of either sex within a species to maximize their reproductive success in varying social and environmental conditions. These tactics often involve different ways of competing for mates or different tactics for parental investment. Conditional ARTs are a class of ARTs where individuals express an ART depending on an extrinsic or intrinsic cue. The fitness of conditionally expressed ARTs may not necessarily be equal for their persistence. However, there exists a class of conditional ARTs called reversible or flexible ARTs wherein individuals reversibly switch between ARTs in response to a cue. In systems which show flexible ARTs, selection could favour genotypes that gives rse to ARTs that have similar fitness. By virtue of the similarity in mating benefits amongst ARTs, individuals can seamlessly switch between ARTs depending on cues without necessarily incurring fitness losses. My thesis attempts to evaluate the mating benefits as a fitness component of flexible ARTs in Oecanthus henryi. Oecanthus henryi is a tree cricket found in the scrublands of the Indian sub-continent. O. henryi males flexibly adopt three different ARTs to obtain mates. Males can either call to attract females or remain silent. Males can adopt a third tactic, called baffling, wherein males call through a hole they make near the centre of a leaf on their host plant. Baffling is known to amplify the call of a male. In the first chapter of my thesis, I used data from a previously conducted mesocosm experiment to study the expression and mating success of calling and silent ARTs under varying predation risk from their natural predator, the green lynx spider (Peucetia viridans). The findings of the study showed that males were equally likely to call or remain silent on a night and the mating successes of both the ARTs were similar across a steep predation gradient. The similarity in mating success across varying ecological contexts may allow individuals to switch between them without incurring mating related costs. Furthermore, silent males were more likely to aggregate around other callers than callers themselves and obtained a majority of their matings by doing so, which suggests that silent males employ satellite behaviour. In the second chapter of my thesis, I explored the adaptive value of satellite behaviour. While literature suggests that individuals employ satellite behaviour to get mates, its relative advantage over other non-bourgeois tactics remains unexplored. Through laboratory experiments, I showed that silent males do not gain additional mating benefits by behaving as satellites, suggesting that satellite strategy may not be the only alternative tactic employed by silent males to get mates. In the third chapter of my thesis, I investigated why baffling is not commonly observed in the field given its amplification advantage over the other two ARTs, silent and calling. Using an individual-based modelling approach, I explored whether frequency-dependent, density-dependent selection or habitat structure could limit the mating success of bafflers. The results of the study showed that the co-existence of these tactics over ecological time scales is facilitated by the spatial structure of the landscape they inhabit, which served to equalize the otherwise unequal mating benefits of the three tactics. In the last chapter of my thesis, I explore the mortality costs of the two ARTs due to predation. Through laboratory experiments using the green lynx spider as the predator, I showed that the three ARTs elicit a very low but similar likelihood of being attacked and the mortality costs related to these attacks are negligible. The findings suggest that the three ARTs are mildly vulnerable to predation by their natural predator. In summary, my thesis demonstrates that the ARTs expressed by O. henryi provide similar mating benefits. The similar mating benefits of the ARTs and negligible mortality costs due to predation may allow O. henryi males to maximise fitness in varying ecological conditions.

Prey traits that facilitate matings and help forage are shaped by a combination of sexual selection and natural selection as they also tend to attract predators. At the ecological scale however, prey individuals manage this predation risk by altering conspicuous traits and behaviours leading to adverse fitness consequences. Therefore, predicting any evolutionary change as an outcome of risk management requires an understanding of the underlying mechanisms governing predator-prey interactions. By developing and addressing theoretical predictions using empirical evidence collected with a combination of field experiments, enclosure experiments, and computer simulations I investigate the following research themes: (a) predation cost of mate searching and fitness consequences of prey defence responses (space use and alternative reproductive tactics), (b) scaling up of individual prey responses to emergent population mating patterns (assortative mating), and (c) the role of habitat choice in potentially structuring populations through assortative mating. Having examined species interactions at individual- and population-level, I then go on to integrate these ideas along with climate into an ecosystem-level framework, to (d) investigate the role of animals in litter decomposition across a precipitation gradient. Based on these results, I develop a framework and link it to my short- and long-term plans which include unifying prey responses in the context of foraging and reproduction, phenotype-environment matching, effect of climate on species interactions, and ecosystem function.

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.

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In nature, a single selection pressure can act on multiple traits of an individual animal, and a single trait of an animal can also be under multiple selection pressures. Given the potential for complex trade-offs acting across multiple traits, it would be more ecologically relevant and meaningful to study multiple traits of an animal in the wild, where they are simultaneously under multiple selection pressures. However, such processes have rarely been examined in animals, especially in their natural habitat. In my thesis, I will examine how risky behavioural traits are expressed under multiple selection pressures and how variation in the expression of multiple risky behavioural traits contributes to an animal’s fitness. I will also examine the correlations between different risky behaviours and test hypotheses for such correlations. I will conduct behavioural experiments on Psammophilus dorsalis in their natural habitat to answer these questions. In my 1st chapter, I will examine how natural and sexual selection factors simultaneously affect decision-making in response to threat in adult male P. dorsalis. In my 2nd chapter, I will examine correlations between multiple risky behavioural traits and their relative effects on fitness in adult male P. dorsalis. In my 3rd chapter, I will examine if the expression of risky behavioural traits is heritable in adult male P. dorsalis.

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.

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