Interactions among multiple selective pressures on the form–function relationship in insular stream fishes

Abstract Relationships between body shape and escape performance are well established for many species. However, organisms can face multiple selection pressures that might impose competing demands. Many fishes use fast starts escaping predator attacks, whereas some species of gobiid have evolved the ability to climb waterfalls out predator-dense habitats. The ancestral ‘powerburst’ climbing mechanism uses lateral undulations move up waterfalls, a derived ‘inching’ rectilinear locomotion. We examined whether fast-start is impacted by imposed from new functional demands climbing. predicted non-climbing would show morphology facilitate evasion, because these fish live consistently with predators not constrained also that, using undulations, powerburst climbers superior inchers. compared across six goby As predicted, exhibited distinct responded more frequently an attack stimulus than Contrary our predictions, we found no differences in among styles. These results indicate pressure need limit prey attacks.