Sex differences in alternative reproductive tactics in response to predation risk in tree crickets

Spatial structure could explain the maintenance of alternative reproductive tactics in tree cricket males

Trait polymorphisms are widespread in nature, and explaining their stable co-existence is a central problem in ecology and evolution. Alternative reproductive tactics, in which individuals of one or more sex exhibit discrete, discontinuous traits in response to reproductive competition, represent a special case of trait polymorphism in which the traits are often complex, behavioural, and dynamic. Thus, studying how alternative reproductive tactics are maintained may provide general insights into how complex trait polymorphisms are maintained in populations. We construct a spatially explicit individual-based model inspired from extensively collected empirical data to address the mechanisms behind the co-existence of three behavioural alternative reproductive tactics in males of a tree cricket (Oecanthus henryi). Our results show that the co-existence of these tactics over ecological time scales is facilitated by the spatial structure of the landscape they inhabit, which serves to equalise the otherwise unequal mating benefits of the three tactics. We also show that this co-existence is unlikely if spatial aspects of the system are not considered. Our findings highlight the importance of spatial dynamics in understanding ecological and evolutionary processes and underscore the power of integrative approaches that combine models with empirical data.

Predator-prey systems as models for integrative research in biology: the value of a non-consumptive effects framework

Predator-prey interactions are a cornerstone of many ecological and evolutionary processes that influence various levels of biological organization, from individuals to ecosystems. Predators play a crucial role in shaping ecosystems through the consumption of prey species and non-consumptive effects. Non-consumptive effects (NCEs) can induce changes in prey behavior, including altered foraging strategies, habitat selection, life history and anti-predator responses. These defensive strategies have physiological consequences for prey, affecting their growth, reproduction and immune function to name a few. Numerous experimental studies have incorporated NCEs in investigating predator-prey dynamics in the past decade. Interestingly, predator-prey systems can also be used as experimental models to answer physiology, cognition and adaptability questions. In this Commentary, I highlight research that uses NCEs in predator-prey systems to provide novel insights into cognition, adaptation, epigenetic inheritance and aging. I discuss the evolution of instinct, anxiety and other cognitive disorders, the shaping of brain connectomes, stress-induced aging and the development of behavioral coping styles. I outline how studies can integrate the investigation of NCEs with advanced behavioral, genomic and neurological tools to provide novel insights into physiological and cognitive health.

Predation risk regulates prey assortative mating by reducing the expected reproductive value of mates

Many animals exhibit size assortative mating (SAM), but how predation affects it remains largely unknown. We hypothesized that predation risk may turn prey less choosy, disrupting SAM, or reduce the expected reproductive value of mates, maintaining SAM but with different size ratio between mates. Using a manipulative field experiment, we found that desert isopods under risk of scorpion predation maintained SAM, but that males that choose and fight over females were on average smaller for a given female size. Less pairs were formed in risky sites, but there were no differences in female sizes and progeny number, size and age near and away from scorpion burrows. Our complementary behavioral experiments revealed that bigger males stayed longer near safe burrows, and won more male-male contests than smaller conspecifics. Our findings highlight that prey can anticipate future costs of predation and use this information to assess the expected reproductive value of mates.

Higher Rate of Male Sexual Displays Correlates with Larger Ventral Posterior Amygdala Volume and Neuron Soma Volume in Wild-Caught Common Side-Blotched Lizards, Uta stansburiana

Several areas of the vertebrate brain are involved in facilitating and inhibiting the production of sexual behaviors and displays. In the laboratory, a higher rate of sexual displays is correlated with a larger ventral posterior amygdala (VPA), an area of the brain involved in the expression of sexual display behaviors, as well as larger VPA neuronal somas. However, it remains unclear if individuals in the field reflect similar patterns, as there are likely many more selective pressures in the field that may also modulate the VPA architecture. In this study, we examined variation in VPA volume and neuron soma volume in wild-caught common side-blotched lizards (Uta stansburiana) from two different populations. In a population from Nevada, males experience high predation pressure and have decreased sexual display rates during the breeding season, whereas a population in Oregon has lower levels of predation and higher rates of male sexual displays. We found that wild-caught males from the population with lower display rates also exhibited decreased VPA volume and VPA neuron cell soma volume, which may suggest that decreased display rate, possibly due to increased predation rate, covaries with VPA attributes.