To call or not to call: Persistence of flexible alternative reproductive tactics in a tree cricket

Abstract

Alternative reproductive tactics (ARTs) are discrete polymorphisms that help maximise reproductive success. Although flexible ARTs are ubiquitous, theoretical predictions for why flexible ARTs persist over evolutionary time have rarely been empirically tested. We hypothesised that flexible ARTs will persist if they have equal fitness benefits under a range of ecological contexts, or, there are trade-offs between ARTs in different ecological contexts and individuals display the most optimal phenotype in a context-dependent manner. Specifically, we investigated predation risk effects on the expression and fitness consequences of two flexible ARTs: acoustic signalling and being silent, expressed by tree cricketOecanthus henryimales. In large outdoor enclosures, we exposed natural populations ofO. henryito three different abundances of their predator, the green lynx spiderPeucetia viridans. Behavioural observations across successive nights revealed that higher predation risk did not alter the expression levels of the male ARTs, despite crickets experiencing differential risk and survival across treatments. Male crickets demonstrated an equal likelihood of calling or remaining silent on a night. ARTs resulted in similar mating success across differential predation risk, supporting the hypothesis that equal fitness benefits of flexible ARTs under a range of ecological contexts explain their persistence.

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

“…To check for the effect of proportion of bafflers on the mating success of the ARTs, we varied the proportion of bafflers in the population. The remaining males are equally partitioned into the caller and silent ARTs, in accordance with empirical findings that show that a male is equally likely to call or remain silent on a night ( Sadiq et al, 2023 preprint).…”

“…a log-normal distribution with mean 2.59 and standard deviation 0.88. The parameters for the log-normal distribution are derived from empirical data ( Sadiq et al, 2023 preprint). If a male does not move within a bush, it may instead move across bushes with probability π m ′ .…”