Balakrishnan, R. — Page 2

bioRxiv2019

A sensory ecological perspective on mate sampling strategies: simulation models and an empirical test

Long-range communication signals play a central role in mate search and mate choice across a wide range of taxa. Among the different aspects of mate choice, the strategy an individual employ to search for potential mates (mate sampling) has been less explored despite its significance. Although analytical models of mate sampling have demonstrated significant differences in individual fitness returns for different sampling strategies, these models have rarely incorporated relevant information on the ecology of signalers and sensory physiology of receivers, both of which can profoundly influence which sampling strategy is optimal. In this study, we used simulation models to compare the costs and benefits of different female mate sampling strategies in an acoustically communicating field cricket (Plebeiogryllus guttiventris) by incorporating information on relative spacing of callers in natural choruses, their signal intensity and the effect of signal intensity on female phonotaxis behaviour. Mating with the louder caller that the female first approaches emerged as the optimal strategy, thus reflecting the importance of physiological mechanisms of sound signal localization (passive attraction) over active sampling. When tested empirically in the field, female behaviour was consistent with passive attraction.

evolutionary biology↗

bioRxiv2018

Is the predation risk of mate-searching different between the sexes?

In animals that communicate for pair formation, generally one sex invests more effort in mate searching. Although searching by males is prevalent in most animals, in orthopteran insects and some other taxa females physically move to localise signalling males who are predominantly sedentary. Although the two sexes thus share mate searching effort in orthopterans, their behavioural strategies are different and sexual selection theory predicts that signalling males may be following the riskier strategy and incurring higher costs. However, relative levels of risk posed by the two mate searching strategies remain largely unexplored. Hence, we estimated the relative predation risk experienced in natural populations by signalling males and responding females. We did this by quantifying predation risk as a probability of mortality in the context of acoustic communication in a tree cricket, Oecanthus henryi from its ecologically relevant predator, a lynx spider, Peucetia viridans. Spiders may perceive calling in males and movement in females by their ability to detect both airborne acoustic cues and substrate-borne vibratory cues. Probability of mortality was quantified by partitioning it into three spatial components at which crickets and spiders interact, using a combination of extensive field observations and manipulative experiments in a semi-natural setup. We found no differences in predation risk faced by calling males and responding females, suggesting that direct benefits offered by males to females upon pair formation may better explain shared mate searching effort between the sexes in orthopterans.

ecology↗