ASYNCHRONOUS TROPHIC NICHE SHIFTS AMONG INVERTEBRATE-FEEDING FISHES ACROSS A CORAL COVER GRADIENT
Unraveling the links between habitat structure, resource availability and the trophic niche is key to anticipate the effects of global change on ecosystems. On coral reefs, recurrent coral bleaching and increasing anthropogenic pressures have led to rapid losses of structural complexity, with implications for food web dynamics. Invertebrate-feeding fishes are one of the most diverse guilds, and benthic invertebrate communities may be reshuffled by coral loss. Ecological theory suggests that, within the same guild, species respond to habitat and resource change in synchrony, resulting in less partitioning and more functional redundancy at the community level. However, whether the trophic niches of invertivorous reef fishes shift across a gradient of reef condition remains undocumented. Here, we combine otolithometry, gut content metabarcoding, and stable isotope analysis to investigate the performance and trophic plasticity and synchrony of six invertivorous fishes from French Polynesia across various states of coral cover. Most species exhibited distinct niche breath in high versus low cover sites. However, the direction and magnitude of trophic niche differences between high and low coral cover sites varied among species, indicating asynchronous differences in trophic niche breadth across the guild. Our findings reveal that habitat loss may not result in one universal response, even within the same guild. Rather, reef invertivores may have asynchronous trophic differentiation, allowing the maintenance of interspecific coexistence even on degraded reefs. Together, these findings suggest that asynchronous trophic responses may contribute to the resilience of coral reef food webs and help sustain biodiversity under habitat degradation.