Predator Communities With Invasive Pike Are Associated With Changes in Parental Care and Brain Gene Expression in Wild Alaskan Stickleback.

Invasive predators can influence prey through direct predation but also via nonconsumptive effects that alter behavior and physiology. Parental care may be particularly sensitive to these effects, as parents must balance offspring investment with survival under predation risk. Here, we examine how predator exposure and predator community composition influence paternal behavior and brain gene expression in wild populations of threespined stickleback (Gasterosteus aculeatus) in southcentral Alaska. We conducted field behavioral assays in lakes with either native predators only or both native predators and invasive northern pike (Esox lucius), by recording changes in male fanning behavior following predator exposure. We then analyzed whole-brain gene expression using RNA sequencing on a subset of males. Stickleback males parented more in lakes with invasive predators compared to lakes with only native predators. However, after exposure to a model predator, neither predator treatment nor lake type significantly explained short-term changes in paternal behavior, suggesting that behavioral responses to acute predation risk are variable or constrained in natural settings. In contrast, transcriptomic analyses revealed 47 differentially expressed genes associated with predator community. Males from lakes with invasive pike showed enrichment of pathways related to protein synthesis and folding, whereas males from native predator-only lakes showed enrichment of immune response pathways. Parenting state showed minimal transcriptional differentiation. These results suggest that while invasive predator effects were less pronounced in short-term behavioral responses, they may be causing cumulative impacts over time, as evidenced by the baseline fanning behavior and gene expression patterns.