Null models to explain highly diverse community of intertidal decapods on a temperate rocky coast in Antofagasta, northern Chile (23º27ʹS)

The decapod fauna on intertidal shores in northern Chile is characterized by its relatively high diversity and abundance due to the presence of continuous upwelling by the Humboldt Current, which results in a high productivity. The decapod fauna on intertidal rocky shores is characterized by coexisting species that inhabits in natural shelters such as cracks and eroded rocks, as well as among macroalgae. We aimed to monitor the brachyuran and anomuran (porcellanid) crabs in three intertidal sites during two periods of time in September-December 2019 in the Antofagasta region, one site without human intervention and two sites in the city of Antofagasta, for which we applied null models in ecology. We assumed that the communities are random, a viewpoint that is more robust because it reduces the risk of error type I. The results of the application of null models on the co-occurrence species revealed that species associations are mainly structured for all sites, whereas the niche-sharing null model revealed that the reported species did not share ecological niches and in consequence there is not interspecific competition. The results would probably indicate that the species of intertidal decapods have a micro-specific ecological-niche differentiation, which would explain the existence of structured pattern in species associations. The results were compared with information for other sites along the continental Chilean coast.