My research investigates how animals manage risk and the consequences of their defense responses on mating patterns, evolutionary processes, and ecosystem dynamics. I employ a mechanistic approach to understand the evolutionary consequences of ecological interactions between species.
Predation risk as a driver for maintenance of evolutionary roles
In most animals that signal to facilitate encounters with mates, males typically contribute more effort compared to females. Classical theory attributes this generality of sex roles in mate searching behaviour to differential sex-biased mortality by predation. To test this idea, I estimated the differential predation cost experienced by mate searchers by employing field surveys and manipulative experiments at multiple spatial scales. I found predation costs to be similar across mate searching contexts suggesting that other costs such as energy expenditure may be a more important driver maintaining the generality of sex roles (Torsekar et al. 2019, Evolutionary Ecology).
Although the causes and consequences of alternative reproductive tactics (ARTs) have been investigated extensively, the mechanisms underlying maintenance of ARTs in populations, such as predation risk, are poorly understood. I hypothesized that increasing predation risk should alter ARTs in sexual signalling males, where calling males should shift to exhibit satellite behaviours. I investigated this condition-dependence of ARTs by manipulating predator-prey ratios in large field enclosure experiments. With increasing predation risk, male crickets altered sexual signalling behaviour from calling to searching. Using simulations, I demonstrated that male searching behaviour is in fact directed towards other calling males, implying satellite behaviour (Torsekar and Balakrishnan 2020, Functional Ecology).
Relevant publications:
Torsekar, V. R., Isvaran, K. and Balakrishnan R. 2019. Is the predation risk of mate-searching different between the sexes? Evolutionary Ecology
Torsekar, V. R. and Balakrishnan R. 2020 Sex differences in alternative reproductive tactics in response to predation risk in tree crickets. Functional Ecology
Habitat mediation in predator-prey interactions
A central focus of my research programme is to integrate space use in predator-prey interactions with prey movement in the context of reproductive behaviour. I have tested predictions of predator-prey space use theory as prey balance mate searching with predator evasion, at two different spatial scales. I demonstrated that in bush-dwelling tree crickets the mate searching behavioural context of individual cricket influences spider overlap at the among bush scale and cricket antipredator movement at the within bush scale (Torsekar and Thaker 2020, Proceedings B).
For investigating how fear of predators affects prey population-level mating patterns, I developed and tested a new theoretical framework predicting how predation risk may influence size assortative mating based on prey perception of risk. Using a large field experiment in the Negev desert, I found that presence of scorpion predators affected size assortative mating by reducing the reproductive value of mates settled in risky habitats. Disentangling the underlying mechanism using complementary behavioural experiments revealed that mate preferences and competitive ability of large males was driving the population-level pattern (Torsekar et al. 2022 Ecology).
I explored whether habitat choice can mediate assortative mating where lower quality individuals proactively choose risky habitats to avoid conflict with their competitors, thereby exhibiting ‘prudent habitat choice’. I found that burrow preference in female isopods is explained by an interaction between body size and habitat quality demonstrating assortative mating may emerge from individuals preferentially occupying certain habitats based on their phenotype, and incidentally mating more often with co-occurring mates. These findings suggest that habitat choice rather than mate choice could lead to assortative mating (Torsekar et al. bioRxiv).
Relevant publications:
Torsekar, V. R. and Thaker, M. 2020 Mate-searching context of prey influences the predator–prey space race. Proc. R. Soc. B.
Torsekar V. R., Zaguri, M. and Hawlena D. 2022 Predation risk regulates prey assortative mating by reducing the reproductive value of mates. Ecology
Torsekar V. R., Lajmi A. and Hawlena D., Prudent burrow site selection in a landscape of fear. bioRxiv.
Ecosystem contributions of macrodetritivores
Traditionally in ecosystem ecology, plant leaf litter decomposition, which plays a crucial part of nutrient cycling in the ecosystem, is attributed to microbial activity. In arid regions – characterised by unfavourable decomposition conditions – it raises the question why plant leaf litter does not accumulate over time. Decomposition by detritivorous arthropods is suggested to play an important role but rarely tested. In collaboration with the Hawlena lab, I am testing a new theory exploring whether the specific contribution of macro-arthropods in reflection of its distribution and functional role across the aridity gradient (Torsekar et al. bioRxiv).
Relevant publications:
Torsekar V.R., Sagi N., Johnson J.D., Hawlena Y., Gavish-Regev E. and Hawlena D., Contrasting responses to aridity by different-sized decomposers cause similar decomposition rates across a precipitation gradient. bioRxiv.