The evolutionary theory of aging proposes that senescence is related to decreased selection against deleterious mutations acting late in life. Senescence, i.e., an increase in intrinsic mortality with age, should reflect levels of extrinsic mortality early in life. We tested these predictions using two species of field cricket, Gryllus integer and Gryllus pennsylvanicus. Gryllus integer males are host to a sex-biased parasitoid fly, which orients to the male calling song. As a result, males have reduced life expectancy compared with females in the field. In contrast, G. pennsylvanicus males and females appear to have similar life expectancies in the wild. Thus, we predicted that there would be a significant species × sex interaction, with G. integer males having the shortest life-span. In two replicates, we found that males of both species died at a significantly younger age than females. However, no evidence of a species × sex interaction was found: in the first replicate, G. integer males died earliest, in the second replicate, G. pennsylvanicus males died earliest.
Behavioral syndromes shape evolutionary trajectories via conserved genetic architecture
