Search

1. Insect cuticular hydrocarbons (CHCs) serve a role in both desiccation resistance and sexual attractiveness. These two functions are thought to be maximised by different CHC compositions, which should lead to local adaptation between populations experiencing different natural and sexual selection pressures. 2. The Pacific field cricket (Teleogryllus oceanicus) is distributed throughout Oceania, including the Hawaiian and Cook Islands. In Hawaii, these crickets face strong natural selection from a parasitoid fly that has promoted the evolution of a novel male reproductive morph, dramatically altering sexual selection in the Hawaiian populations. The parasitoid and male polymorphism do not occur in the Cook Islands. 3. We captured male and female T. oceanicus on two Hawaiian Islands and three Cook Islands, and quantified their CHCs. We also measured temperature and RH at our collection sites to test for associations with cricket CHC profiles. 4. We discovered significant sexual dimorphism in CHC profiles, as well as differences between both island chains and particular islands. The two male reproductive morphs in Hawaii showed distinct CHC expression. There were no associations between weather variables and CHC profiles. 5. Observed differences in T. oceanicus CHC profiles appear to reflect geographic isolation rather than selection in response to local and environmental and social conditions. [ABSTRACT FROM AUTHOR]

Among the parasites of insects, endoparasitoids impose a costly challenge to host defenses because they use their host's body for the development and maturation of their eggs or larvae, and ultimately kill the host. Tachinid flies are highly specialized acoustically orienting parasitoids, with first instar mobile larvae that burrow into the host's body to feed. We investigated the possibility that Teleogryllus oceanicus field crickets employ postinfestation strategies to maximize survival when infested with the larvae of the parasitoid fly Ormia ochracea. Using crickets from the Hawaiian Islands of Kauai, where the parasitoid is present, and crickets from the Cook Islands (Mangaia), where the parasitoid is absent, we evaluated fitness consequences of infestation by comparing feeding behavior, reproductive capacity, and survival of males experimentally infested with O. ochracea larvae. We also evaluated mechanisms underlying host responses by comparing gene expression in crickets infested with fly larvae for different lengths of time with that of uninfested control crickets. We observed weak population differences in fitness (spermatophore production) and survival (total survival time postinfestation). These responses generally did not show an interaction between population and the number of larva hosts carried or by host body condition. Gene expression patterns also revealed population differences in response to infestation, but we did not find evidence for consistent differences in genes associated with immunity or stress response. One possibility is that any postinfestation evolved resistance does not involve genes associated with these particular functional categories. More likely, these results suggest that coevolution with the fly does not strongly select for either postinfestation resistance or tolerance of parasitoid larvae in male crickets. [ABSTRACT FROM AUTHOR]

Sexual signal evolution may present fitness consequences for the non‐signaling sex due to shared genes and altered social conditions, but this is rarely studied in natural populations. On the Hawaiian Island of Kauai, most male Teleogryllus oceanicus (Pacific field crickets) lack the ability to sing because of a novel wing mutation (flatwing) that arose and spread in <20 generations. Obligately silent flatwing males have been highly successful because they avoid detection by a deadly, acoustically‐orienting parasitoid fly. Little is known about how the flatwing mutation and resulting song‐less acoustic environment affects female fitness. We found that Kauai females carrying the flatwing allele invested less in reproductive tissues and experienced more instances of mating failure than normal‐wing‐carrying females, though total offspring production did not differ between female genotypes. Females from Oahu (HI, where the parasitoid and flatwing also occur) and Mangaia (an island in the Cook Islands which harbors neither the parasitoid nor flatwing) invested less in reproductive tissues when reared in a song‐less acoustic environment. Kauai females did not exhibit this plasticity, perhaps because they have experienced nearly song‐less conditions for the past ~15 years following the establishment of flatwing. We show that female T. oceanicus experience a mix of costly and beneficial effects of sexual signal loss, which should help maintain the wing polymorphism in the wild. Our results demonstrate that the non‐signaling sex can experience a nuanced set of phenotypic consequences resulting from signal evolution, which can further shape dynamics of sexual signal evolution. [ABSTRACT FROM AUTHOR]