Environmental Influence on Stickleback Fish Phenotype

Abstract Sticklebacks have grown to be a model organism in the last few decades because they have undergone a rapid adaptive radiation event. Portions of the original marine population have migrated to isolated freshwater ecosystems and their fundamental niche has expanded. Variation among select phenotypic traits is a direct result of selective pressures imposed by new environment types. Lateral plates have been the most widely analyzed trait, it is hypothesized that great variation in plate quantity has resulted from expansion events. Lateral plates are pieces of an exoskeleton in addition to the already established endoskeleton. This study aims to assess observable discrepancies between stickleback fish populations inhabiting different environments, 13 papers were recovered providing insight about shifts in water chemistry, selection, habitat-specific predators, and the genetic history of the Eda locus. The Eda locus is the specific gene that is linked to variation in lateral plates. Of these 13 studies, 5 were chosen for inclusion of data in this meta-analysis. Papers were included or excluded based on how data was collected and reported, and the environments from which they took samples. Saltwater and freshwater habitats make up the treatment groups, or predictor variable. The effect size was measured as the average lateral plate count. Results indicated that there is no significant difference in lateral plate count between saltwater and freshwater stickleback populations (SMD: -17.63, 95% CI: -38.91 – 3.64). Heterogeneity appeared to be very high between the 5 samples, it was important that I assess the diversity among methods. For future research, it would be advantageous to incorporate multi-dimensional questions, provide detailed observations and calculations, and form collaborative teams