Taxonomic and functional richness of fish in temperate and tropical reefs of the Mexican Pacific

Taxonomic and functional diversity patterns of fish in temperate reefs in the Mexican Pacific have not been analyzed in integrative biodiversity studies. Thus, this study compared the taxonomic, phylogenetic, and functional diversity of reef fish in 4 biogeographic provinces: Californian, Cortez, Panamic, and Oceanic Islands. Species checklists were compiled from the literature, museum collections, and monitoring data from 21 sites in marine protected areas (MPAs) and 45 non-protected sites. Based on this data and 6 biological traits (size, mobility, period of activity, gregariousness, position in the water column, and diet), we calculated species richness (S), average taxonomic distinctness (Δ+), number of functional entities (FE), functional redundancy (RED), functional vulnerability (FV), and functional volume (FVol). We registered 1,045 species; the dominant categories were benthic, highly site-attached, diurnal, solitary, medium-sized, and invertivores. The Cortez province showed the highest S and FE values, whereas the Californian province presented the lowest values. Notably, FVol was >70% across the 4 biogeographic provinces, suggesting that the range of ecological functions and processes was maintained across provinces despite their contrasting biodiversity levels, environmental conditions, and evolutionary histories. A “regional backbone” was identified, consisting of 74 species and 58 FE (the fundamental species and shared ecological roles across provinces). At the regional level, low RED (<3 species·FE–1) and high FV (>55% of FEs represented by a single species) were observed. All provinces presented high values of Δ+ (>80%), reflecting the broad range of taxonomic lineages within the region. The MPAs presented higher S and RED than non-protected sites; however, further research is needed to elucidate the positive effects of protection.