Alternative reproductive tactics (ARTs) are distinct phenotypes that individuals of a species use to maximize reproductive success. This thesis investigates the persistence and adaptive value of flexible ARTs in male tree crickets, Oecanthus henryi, which employ calling, remaining silent, and baffling (calling through a hole in a leaf to amplify sound) to attract mates. By examining the impact of predation risk, the effectiveness of satellite behaviour, the uncommon use of baffling despite its advantages, and the mortality costs associated with different ARTs, this research aims to understand how these tactics coexist and maintain similar fitness benefits across various ecological contexts.
In the first chapter, I briefly introduce the subject of alternative reproductive tactics, their various modes of expression and their persistence in natural populations. I draw attention to the general lack of understanding concerning the fitness components of flexible ARTs. I highlight various factors that can affect the fitness of ARTs. I introduce the model system Oecanthus henryi and justify its use for studying flexible ARTs. Using data from a mesocosm experiment, the second chapter explores how predation risk from the green lynx spider (Peucetia viridans) affects the expression and mating success of calling and silent ARTs. The results show that males are equally likely to call or remain silent regardless of predation risk, and both tactics result in similar mating success. Silent males often aggregate around callers, potentially employing satellite behaviour to gain mates. The third chapter examines the adaptive value of satellite behaviour through laboratory experiments. It was found that silent males do not gain additional mating benefits by acting as satellites, suggesting that this may not be the only alternative tactic for silent males to obtain mates.
Despite its amplification advantage, baffling is rarely observed in the field. Using individual-based modeling, the fourth chapter investigates whether frequency-dependent and/or density-dependent selection, or habitat structure, limits the success of bafflers. The findings indicate that spatial structure of the habitat helps equalize mating benefits among the three tactics, facilitating their coexistence over time. The fifth chapter assesses the predation risks associated with the three ARTs. Laboratory experiments reveal that all three tactics have low and similar likelihoods of being attacked by green lynx spiders, with negligible mortality costs.
      The thesis concludes that the similar mating benefits and low mortality costs associated with the ARTs allow Oecanthus henryi males to switch between tactics without incurring significant fitness losses. This flexibility helps maximize reproductive success in varying ecological conditions, supporting the persistence of flexible ARTs in this species.