Key drivers and functional significance of sensory and behavioral trait divergence across multiple environmental stressors in an African cichlid

Ohio State University, The, Columbus OH

Investigators

Abstract

Humans rely intimately on Earth's limited freshwater resources but have disproportionately altered aquatic systems through degradation of water quality. Although this has led to the extinction of many freshwater fish species, some fish species are able to cope and persist despite rapid and severe changes in the environment. In order to predict and curb additional extinctions, there is a critical need to discover what traits might allow some species to persist while others go extinct. This project aims to identify how fish adapt and persist under altered environmental conditions; for example, by asking how fish find mates and reproduce if water clarity is reduced due to muddy run-off from deforested slopes. To accomplish this goal, this project will examine the responses of a wide-spread tropical freshwater fish in Uganda that has persisted under conditions of decreased water clarity and oxygen availability resulting from human activities such as agriculture and deforestation. The study combines surveys of wild-caught fish that develop and live under the inherent variation in natural systems with controlled experiments in the laboratory. This approach provides a unique opportunity to tease apart those traits that allow this fish species to survive and reproduce across a range of environmental stressors. The influence of degraded water quality on fish and humans is of global concern; therefore, this project also aims to create connections between youth in Uganda and in Ohio through a water quality education and virtual exchange program. Although human-induced rapid environmental change (HIREC) often leads to biodiversity loss, some species are able to cope with multiple environmental stressors through phenotypic plasticity and/or genetic evolution. Phenotypic change in response to HIREC has been documented in a broad array of taxa; however, we understand very little about when phenotypic change is adaptive and promotes population persistence or is maladaptive and leads to population decline. The proposed project will address the central hypothesis, based on extensive pilot data, that phenotypic changes driven by multiple environmental stressors (e.g. hypoxia and turbidity) are functionally significant and that these trait differences confer fitness advantages under naturally occurring combinations of the stressors. Specifically, the goal is to link HIREC-driven phenotypic change with the adaptive value of trait changes, by determining (1) the functional significance of trait changes, and, (2) the mechanisms by which trait changes confer a fitness advantage. This will be accomplished by taking advantage of known divergence in sensory and behavior traits associated with reproduction in populations of an African cichlid fish experiencing extremes of multiple environmental stressors. The approach proposed will advance our understanding of the key drivers and functional significance of phenotypic change in human-impacted aquatic ecosystems by specifically linking individual phenotype with fitness across generations. More broadly, such understanding will allow predictions to be made about species persistence and mitigation of biodiversity loss under HIREC.