Rapid evolution and behavioral plasticity following introduction to an environment with reduced predation risk

Abstract

Adaptive behavioral plasticity can play a beneficial role when a population becomes established in a novel environment if environmental cues allow the expression of appropriate behavior. Further, plasticity itself can evolve over time in a new environment causing changes in the way or degree to which animals respond to environmental cues. Colonization events provide an opportunity to investigate such relationships between behavioral plasticity and adaptation to new environments. Here, we investigated the evolution of behavior and behavioral plasticity during colonization of a new environment, by testing if female mate‐choice behavior diverged in Trinidadian guppies 2–3 years (~6–9 generations) after being introduced to four locations with reduced predation risk. We collected wild‐caught fish from the source and introduced populations, and we reared out second‐generation females in the laboratory with and without predator cues to examine their plastic responses to a bright and dull male. We found introduced females were less responsive to males when reared without predator cues, but both introduced and source females were similarly responsive when reared with predator cues. Thus, the parallel evolution of behavior across multiple populations in the low‐predation environment was only observed in the treatment mimicking the introduction environment. Such results are consistent with theory predicting that the evolution of plasticity is a by‐product of differential selection across environments.

Resurrecting the metabolome: Rapid evolution magnifies the metabolomic plasticity to predation in a natural Daphnia population

“…in Trinidadian guppies when prey shift to a situation with relaxed predation pressure (Westrick et al, 2019). Our results during the second transition match with the only other study reporting a correlation between ancestral plasticity and evolution at the molecular level.…”

“…This matches the reduced plasticity for multiple life‐history, morphology and behaviour traits in D . magna during the second transition (Stoks et al, 2016), as also has been observed in Trinidadian guppies when prey shift to a situation with relaxed predation pressure (Westrick et al, 2019). Our results during the second transition match with the only other study reporting a correlation between ancestral plasticity and evolution at the molecular level.…”

Rapid evolution and plasticity of genitalia

“…Czesak et al, 2006; Via & Lande, 1985), as has been observed in guppies for other traits (e.g. Handelsman et al., 2013; Torres‐Dowdall et al, 2012; Westrick et al, 2019).…”

“…We found longer genitalia in the source population that coexists with major predators, consistent with the sexual conflict hypothesis (Arnqvist & Rowe, 2002) since forced copulation rates are higher in high‐predation environments (Evans et al., 2011; Liley & Luyten, 1985; Magurran & Seghers, 1994). In these same populations, females did not exhibit a preference for more colourful males (Westrick et al, 2019), further suggesting mate choice may not be as important as sexual conflict in this case, but introduced females also spent less time investigating and associating with males (Westrick et al, 2019), which suggests gonopodia should have increased, not decreased in length, to improve forced copulations as a strategy to mate with unresponsive females. Thus, our results are consistent with the growing body of work implicating sexual conflict in gonopodium evolution (e.g.…”

“…The slopes of the reaction norms are retained, indicating a similar response among populations to the rearing treatments (Figure 3). Recent work in the guppy system has documented a repeated pattern of increased plasticity in populations introduced to low‐predation environments for morphological, life‐history, physiological and behavioural traits (Fischer et al, 2013; Handelsman et al., 2013; Torres‐Dowdall et al., 2012; Westrick et al, 2019). However, while plasticity did not evolve, we hypothesize plasticity may have contributed to rapid evolution by increasing the strength of selection on the gonopodia.…”