Latitudinal gradients of dispersal and niche processes mediating neutral assembly of marine fish communities

Elucidating the relative importance of niche and neutral processes in structuring ecological communities is a major goal of ecology. We considered multiple components of community structure (beta diversity, species abundance distributions, and niche specialisation) and spatial scales to identify the processes structuring marine fish communities along a tropical to temperate gradient. Beta diversity was explained by local scale environmental and spatial variables, with geographic distance and environmental gradients being stronger drivers of species turnover in tropical and temperate study areas, respectively. Species abundance distributions found a significant component of community structure in all regions to not differ from that expected by chance. Niche specialisation was more prevalent among the endemic, temperate fish species than in tropical fishes. Our results support a strong neutral component of marine fish community assembly, regardless of bioregion. A change in importance from dispersal limitation to niche filtering processes was found from tropical to temperate communities, superimposed over neutrally assembled marine fish communities.