Sexual conflict and sexually dimorphic cognition—reviewing their relationship in poeciliid fishes

Abstract

Abstract: Sexual conflict, the difference in preferred mating rates between the sexes, often leads to sexually dimorphic morphologies, strategies, and behaviors. We are now beginning to realize that this pervasive evolutionary process has implications for variation in cognition as well. Here, I review the evidence for this in poeciliid fishes with a focus on taxa that exhibit high levels of sexual conflict (Gambusia affinis, G. holbrooki, Poecilia reticulata) as well as taxa that represent a more moderate level of sexual conflict (Xiphophorus nigrensis). Sexually dimorphic behaviors emerge across poeciliids in predictable directions consistent with sexual conflict and associated with sex-specific variation in cognition. For instance, poeciliid females have evolved a suite of behaviors that reduce male harassment, including greater shoaling tendencies and risk sensitivities than males. Meanwhile, cognitive styles and cognitive-behavioral profiles diverge between the sexes in ways that highlight these behavioral differences likely born from conflict. Male and female G. affinis have opposing relationships between exploratory tendencies and learning, and they also exhibit distinct behavioral predictors (sociability, activity, anxiety, and exploratory behaviors) for individual learning performance. Artificial selection studies suggest that increases in sexual conflict lead to a demand in cognitive processes; and neurogenomic studies reveal that specific brain regions and molecular pathways underlying high and low sexual conflict interactions may differ. While the current body of evidence is still nascent in many respects, I will highlight areas of research in which further investigation with poeciliid fishes can provide insight into the intertwined relationship between sexual conflict and cognition. Significance statement: Rarely does one consider the benefits of conflict. However, when it comes to sexual conflict, one of the potential benefits it may bring is advances in cognition. I use the poeciliid fishes to showcase this idea as they are both a model for sexual conflict and an experimentally tractable system to test for cognitive variation. I review the current evidence across poeciliid fishes that sexual conflict drives behavioral changes, physiological investment in brain size, and neuromolecular responses within the brain. Furthermore, I examine sexually dimorphic relationships between learning performance and behavioral traits. While all the data reported in this review come from poeciliid fishes, the evolutionarily conserved nature of the decision-making network across vertebrate brains suggests the reported patterns may have relevance to a diversity of vertebrates (including humans) that experience high degrees of sexual conflict.