Managing the tradeoff between reproduction and survival requires flexibility in behavior and gene regulation in threespined stickleback
Predators exert a powerful selective force, however predatoravoidance can conflict with other important activities such as attracting mates. Decisions over whether to court mates versus avoid predators are vital to fitness, yet the mechanistic underpinnings of how animals manage such tradeoffs are poorly understood. Here, we investigate flexibility of behavior and gene regulation in response to a tradeoff between avoiding predators (survival) and courting potential mates (reproduction) in threespined stickleback (Gasterosteus aculeatus). We compared behavioral and transcriptomic responses of male sticklebacks faced with a courtship opportunity and cues of a predator simultaneously to males faced with a courtship opportunity or cues of a predator alone, and found that males behaviorally compromised courtship in favor of predator avoidance when faced with a tradeoff between them. The need to manage this tradeoff elicited dynamic changes in brain gene expression, and sets of functionally-connected genes were organized into discrete modules based on co-expression. Additionally, we found that behavioral flexibility in response to tradeoffs corresponded to flexibility in gene regulatory network structure. Combined, these results uncover the coordinated response by the brain to a fundamental ecological tradeoff, providing insight into the structure and function of genetic networks underpinning how animals make fitness-influencing decisions. Overall design: In this study, we presented male sticklebacks with a tradeoff between courtship and predation risk and compared their brain transcriptomic resposne to males faced with a courtship opportunity alone, cues of a predator alone, or a control.