Feeding selectivity and a functional trade-off in a benthic fish with a continuous morphological variation: an...

Area of Science:

• Ecology
• Evolutionary Biology
• Animal Behavior

Background:

• Phenotypic divergence is often driven by functional trade-offs under divergent selection.
• Intermediate phenotypes can have lower fitness in trade-off scenarios.
• Non-discrete phenotypic variation, including intermediates, poses a challenge to understanding divergence mechanisms.

Purpose of the Study:

• To investigate the mechanisms maintaining non-discrete phenotypic variation in a fish population.
• To examine morphology-dependent feeding selectivity and functional trade-offs in Pseudogobio esocinus.
• To understand how trait variability persists without divergence under divergent selection.

Main Methods:

• Laboratory experiment with benthic cyprinid fish (Pseudogobio esocinus).
• Simultaneous presentation of two prey types (chironomid larvae and amphipods).
• Observation of prey utilization and feeding behavior based on mouthpart morphology.

Main Results:

• Narrower-mouthed fish consumed a higher proportion of secondary prey (amphipods) by altering feeding behavior.
• Wider-mouthed fish primarily consumed chironomid larvae.
• Intermediate-mouthed fish exhibited lower feeding efficiency, suggesting a potential disadvantage.

Conclusions:

• Morphology-dependent feeding performance and functional trade-offs can impact trait variability, potentially favoring specialization.
• Environmental factors like fluctuating prey availability may relax trade-offs, allowing coexistence of extreme and intermediate phenotypes.
• This study provides insights into mechanisms maintaining phenotypic variation within a single habitat, even with trade-offs.