Inter-individual differences in ontogenetic trophic shifts among three marine predators

Area of Science:

• Marine biology
• Ecology
• Isotope geochemistry

Background:

• Ontogenetic niche shifts are common in animals.
• Individual differences in size, morphology, sex, and personality can influence behavior and trophic interactions.
• Understanding these variations is crucial for population dynamics and ecological monitoring.

Purpose of the Study:

• To quantify intraspecific variation in trophic shifts across different body sizes in three shark species.
• To investigate how environmental context influences these ontogenetic trophic shifts.
• To assess the implications of phenotypic variability for population and community responses to environmental change.

Main Methods:

• Stable carbon and nitrogen isotope analysis of shark tissues.
• Sampling of spurdogs (Squalus spp.) in deep-sea habitats, bull sharks (Carcharhinus leucas) in estuarine habitats, and blacktip reef sharks (Carcharhinus melanopterus) in coral reef ecosystems.
• Analysis of trophic variation in relation to body size and ecological context.

Main Results:

• Spurdogs showed limited trophic variation that decreased with body size.
• Bull sharks exhibited greater individual differences in trophic shifts, which decreased with ontogeny.
• Blacktip reef sharks displayed increased intraspecific variation in trophic interactions with increasing body size.

Conclusions:

• Environmental stability may influence population variability; more variable environments may support greater individual differences in trophic interactions.
• Understanding the factors promoting or dampening phenotypic variability is essential for predicting ecological responses to environmental disturbance.
• Results highlight the importance of considering individual variation in trophic ecology for conservation and management.