Do Florida and Belize populations of mangrove rivulus differ in aggression and fecundity?

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Lopez, Jonathan
Barbosa, Angela
McGhee, Katie
Issue Date
Scholarship Sewanee 2021 , Biology , Evolution , Behavioral Plasticity , Predation , Genetics
In many species, aggressive behaviors are crucial to determining the outcome of dominance interactions and to successfully defend a territory. However, being overly aggressive can be costly in terms of injury as well as potentially suppressing reproduction. Thus it remains unclear what shapes the aggression that individuals display in dominance interactions. Is aggression shaped by the environment or is there genetic variation in aggressive behavior within and among populations? In this study we explored this question using genetically distinct clones of the self-fertilizing hermaphroditic mangrove rivulus (Kryptolebias marmoratus) collected many generations ago from populations in Florida and Belize. We paired individuals within their respective genetic clones and examined whether there were differences among populations in their aggression during dominance interactions and their production of embryos after these dominance interactions. The larger fish of the pair was put into the testing tank overnight, thereby establishing the tank as their territory (and dominant) while the smaller fish of the pair (from the same clone) was introduced at the start of the trial the next day. We then recorded the number of dominance displays, attacks, and chases performed by each partner. Individuals from Florida showed more dominance displays, attacks, chases, and overall aggressive behaviors in these dominance interactions compared to individuals from Belize. Although genetically distinct, genetic clones from the same population showed similar behavior within a population. Additionally, individuals from Belize produced more embryos than individuals from Florida after dominance interactions. This pattern is consistent with a suppressive effect of aggression and stress on reproduction. Why different levels of aggression might be favored in these populations remains unclear and ecological differences are clearly an interesting area for future research. Despite several generations of selfing and being reared in a common garden, population differences in aggression and fecundity seem to persist in the lab, suggesting genetic differences. Our results suggest that aggression and fecundity are shaped by both genetic and environmental factors that can vary among populations.