Meeting Abstract
31.3 Friday, Jan. 4 Are all eggs created equal? Food availability and the fitness tradeoff between reproduction and immunity STAHLSCHMIDT, ZR*; ROLLINSON, N; ACKER, M; ADAMO, SA; Dalhousie University; Dalhousie University; Dalhousie University; Dalhousie University zrs@dal.ca
Reproduction and self-maintenance (e.g., immune function) are critical processes, but organisms can rarely optimize both of these traits. Such reproduction-immunity tradeoffs may be “facultative” and appear only when resources are scare, or they may be “obligate” and occur regardless of resource availability due to underlying physiological mechanisms. While the role of resource availability in reproduction-immunity allocation tradeoffs has been studied, measuring resource allocation alone may be insufficient when gauging the fitness consequences of reproduction-immunity tradeoffs. Thus, we used the Texas field cricket (Gryllus texensis) to provide the first test of whether resource availability influences a fitness tradeoff between these two traits—that is, how does chronic food limitation and immune challenge affect lifetime fecundity and reproductive success? We used a 2 x 3 design to manipulate food availability and immune status throughout adulthood in a factorial fashion. We demonstrate that reproduction-immunity tradeoffs are “obligate” in crickets because immune challenge resulted in reduced fecundity and reproductive success regardless of food availability. Food availability significantly affected fecundity, reproductive success, and hatchling size where females with ad libitum access to food produced more abundant and larger hatchlings. There was no effect of food availability or immune status on egg size, egg phenoloxidase activity, incubation duration, hatching success, or hatchling energy stores. In sum, we clarify the independent and interactive roles of two widespread environmental factors (food availability and immunogen exposure) on the dynamics of reproduction. Future work will investigate the underlying role of immune-induced oxidative damage in reproduction-immunity tradeoffs.
