Community Assembly Processes in Tropical Intertidal Rockpool Fishes

Understanding the drivers of community assembly in extreme and dynamic environments, such as intertidal rockpools, requires the integrated assessment of environmental filtering, species traits, phylogeny, and species interactions. This study aimed to quantify the multi‐faceted drivers of rockpool fish assemblage structure by examining: (a) the association with physical and structural pool attributes, (b) the influence of species functional traits and phylogenetic relatedness, (c) residual co‐occurrence patterns suggestive of species interactions, and (d) temporal and spatial dynamics. The assemblage was dominated by a few resident species (e.g., Bathygobius ramosus , Tomicodon zebra ), which comprised 72% of total abundance. Rockpool volume and substratum rugosity were the primary environmental drivers, explaining a substantial portion of the variation in abundance for most of the 15 species studied. While species' traits (e.g., body size, trophic level, water column position) were associated with ~28%–67% of the niche variation across environmental gradients, there was no significant phylogenetic signal in species responses. After accounting for these environmental, spatial, temporal, and trait‐based factors, significant positive residual co‐occurrences were prevalent, most notably a strong association between B. ramosus and Abudefduf concolor suggesting potential facilitative interactions or shared unmeasured niche axes. These findings demonstrate that the structure of intertidal rockpool fish assemblages is predominantly filtered by key structural habitat features. The lack of a phylogenetic signal and the prevalence of positive co‐occurrences highlight that species‐specific traits and potential facilitative interactions, rather than evolutionary history, are critical in shaping these dynamic communities.