Functional Diversity of Reef Fishes Varies Across Oceanic, Coastal-Influenced, and Coastal Reefs in the Mexican Eastern Tropical Pacific

The Eastern Tropical Pacific (ETP) comprises several coral ecosystems, which are distributed across a variety of coastal zones and oceanic islands. In these ecosystems, reef fish play key roles in their functioning. In ETP, there is a paucity of studies that have evaluated fish functional diversity (FD) and compared oceanic and coastal systems from a predominantly trophic perspective. A comparative analysis was conducted on fish FD in seven coral ecosystems, encompassing three distinct environmental contexts: (1) Oceanic, (2) Coastal-influenced, and (3) Coastal. The hypothesis that FD varies spatially along this oceanic–coastal gradient is predicated on the premise that such variation is attributable to differences in disturbance regimes and environmental conditions. Our results show that not all functional α-diversity indices exhibited significant variation among zones. However, analysis of functional dominance, divergence, dispersion, and β-diversity analyses revealed clear spatial variation in functional structure, partially supporting expectations related to disturbance regimes across the oceanic–coastal gradient. These patterns may be indicative of increasing disturbance intensity, in conjunction with other interacting processes such as variability in larval supply, recruitment dynamics, and environmental conditions, including fishing pressure, sedimentation, nutrient inputs, and coastal upwelling. The findings of this study demonstrate the efficacy of functional diversity metrics in assessing reef fish responses to both natural and anthropogenic disturbances. In addition, the present study offers actionable insights with regard to the formulation of conservation and management strategies in the Mexican Eastern Tropical Pacific.