COS 274-2 - CANCELLED - Plasticity and evolution of brain morphology in divergent Trinidadian guppies

Background/Question/Methods

As ecosystems change, it is crucial to understand the characteristics of organisms that allow them to survive in changing and diverging habitats. Phenotypic plasticity is a critical mechanism generating variation in traits across habitats. Plasticity is usually studied under relatively simple paradigms without considering the interaction of multiple environmental factors or the potential for divergence in plasticity itself, limiting our understand of how plasticity might shape phenotypes under the complexity of natural conditions. Trinidadian guppies (Poecilia reticulata) are known for their repeated adaptation to high- (HP) and low-predation (LP) environments. These habitats differ in several ecological characteristics, including level of predation threat and conspecific density. Guppies in these habitats differ in life history, morphology, and behavior. We used this system to examine the evolution of plasticity and the impact of multiple environmental cues on the development of brain morphology, including brain size and the proportional size of different brain regions. We performed a plasticity study using second-generation offspring of individuals collected from HP and LP sites in Trinidad. We exposed these individuals to two different kinds of environmental cues: perceived predation threat (predator cue presence vs absence) and conspecific density (reared in isolation or with conspecifics).

Results/Conclusions

Preliminary results indicate that brain morphology does show phenotypic plasticity in response to predator cues, with fish developing larger brains and larger volumes of certain brain regions in the high predator treatment. Furthermore, differences in plastic responses between collection sites and sexes indicate the potential for evolved differences in plasticity. Further results will test impacts of multiple environmental cues on brain morphology. These results will expand our understanding of the complexity and evolution of phenotypic plasticity and brain variation. More broadly our study suggests the importance of plasticity as a mechanism that allows for ecological diversification and organismal performance.