Effects of inbreeding on life-history traits and sexual competency in decorated crickets

Abstract

Although inbreeding depression in life-history traits has been well characterized, inbreeding effects on mating behaviour and sexually selected traits have been less well studied. Here, we assess levels of inbreeding depression in a number of fitness-related reproductive parameters of female decorated crickets, Gryllodes sigillatus. We predicted that due to direct negative effects of inbreeding and a potential trade-off between reproduction and current survival, as suggested by effects of inbreeding on immunity, inbred females would show significantly reduced reproductive output compared with outbred females. We also examined sex-specific effects of inbreeding on mating competency, focusing specifically on the female's decision to mount a male and the male's ability to transfer a spermatophore. We predicted that any inbreeding depression in sexual competency should be more evident in the success of spermatophore transfer than in female mounting propensity because of the tighter link between mating success and fitness in males than in females. Inbred females produced fewer offspring with longer development times compared with outbred females, results consistent with theory, as inbreeding depression is expected to be more severe for traits more tightly coupled with fitness. Inbreeding also had sex-specific effects on sexual competency. Inbred females were less likely to mount outbred males than were outbred females to mount inbred males. Inbred males were significantly less likely than outbred males to transfer a spermatophore regardless of female inbreeding status. These results reveal that inbreeding may have unexpected consequences for sexual competency and highlight the importance of considering mating behaviour when assessing effects of inbreeding within populations.