Increases in predation favor evolutionary shifts in behavioral plasticity in Trinidadian killifish

Behavioral plasticity is expected to be favored in risky environments, such as when prey species coexist with predators, because prey must alternate between fitness related foraging/mating behaviors and antipredator behaviors that enhance survival. We compared behavioral plasticity in Trinidadian killifish that are found in sites with and without predators. We quantified aggressive and antipredator behaviors via a mirror assay in second-generation lab-reared and wild-caught killifish before and after exposure to predator cues. We compared two types of aggression including: overt aggression (ramming, biting, lunging, tail-slapping) and display aggression (spine arching, bending into an s-shape, and opercular flaring). We additionally compare the amount of time the fish spent frozen as a proxy for anti-predator behavior. We show clear differences in plasticity between populations with and without predators. Killifish from sites with predators decreased overt aggression in response to exposure to predator chemical cues. Killifish from sites that lack predators showed a higher degree of canalization in aggression presumably due to the high competition they face in those locales. Interestingly, wild fish from sites without predators retain the ability to detect the predator cue and respond by decreasing overt aggression and increasing time spent frozen, though to a lesser degree compared to the fish from sites with predators. Our results support the expectations that development in a risky environment favors evolutionary changes in predator-mediated behavioral plasticity.

Methods
The following data sets were collected from second-generation lab-reared and wild-caught Trinidadian killifish (Anablepoides hartii) in 2023. They represent a predator cue experiment in which fish were assayed for aggression and antipredator behaviors before (pre-trial) and after (pre-trial) introduction of a predator odor cue to determine how predator presence influences behavior. The data are in long-format to facilitate repeated measures analyses.