Trans-generational but not early life exposure to stressors influences offspring morphology and survival.

Abstract

Environmental changes, such as the introduction of non-native species, can impose novel selective pressures. This can result in changes in fitness-relevant traits within an individual's lifetime or across multiple generations. We investigated the effects of early life versus trans-generational exposure to a predatory invasive insect stressor, the red imported fire ant (Solenopsis invicta), on the morphology and survival of the eastern fence lizard (Sceloporus undulatus). We captured gravid lizards from high-stress populations with long histories of invasion by fire ants and from uninvaded sites. Resulting hatchlings were exposed weekly to one of the three treatments until they reached maturity (42weeks): (1) sub-lethal attack by fire ants; (2) topical application of the stress-relevant hormone, corticosterone (CORT), to mimic the stress of fire ant attack; or (3) control handling. Exposure to post-natal early life stress (fire ants or CORT) did not interact with a population's evolutionary history of stress to affect morphology or survival and early life stress did not affect these fitness-relevant traits. However, morphology and survival were associated with the lizards' evolutionary history of exposure to fire ants. Offspring of lizards from fire ant invaded sites had longer and faster growing hind-limbs, gained body length and lost condition more slowly in the first 16weeks, and had lower in-lab survival to 42weeks, compared to lizards from uninvaded sites. These results suggest that a population's history of stress/invasion caused by fire ants during ca. 38 generations may be more important in driving survival-relevant traits than are the early life experiences of an organism.