Species abundance is directly impacted by environmental variables (e.g., precipitation, temperature, salinity) and interspecific interactions (e.g., community members). Disentangling abiotic and biotic drivers of species abundance is critical to understanding current species distributions, species coexistence, and the potential disintegration of communities with the progression of climate change. Intertidal habitats are highly heterogenous with environmental factors varying dramatically over short spatial scales. In situ environmental conditions are influenced by local climate, the surrounding ocean, and their interaction. Furthermore, the magnitude of oceanic impact is directly mediated by the frequency of tidal inundation. In these intertidal habitats, species often segregate either due to abiotic factors or strong interspecific interactions. By leveraging climatic, marine, tidal, and topographic data with 323 surveys for five fish species (Kryptolebias marmoratus, Fundulus confluentus, F. grandis, Poecilia latipinna, Gambusia spp.) in a hierarchal Bayesian model, we evaluate: i) which variables impact species abundance, ii) species-specific responses to abundance covariates, and iii) species-specific microhabitat dependence. We further investigate the role of community member abundance on a euryhaline intertidal species, Kryptolebias marmoratus (henceforth “rivulus”), to disentangle to impact of environmental conditions and interspecific interactions on its abundance.
Results/Conclusions
For these mangrove fish species, we demonstrate that different sets of biotic and abiotic factors affect detection probabilities and estimated abundance, as well as the direction and magnitude of their effects. The model showed that the five species differ in microhabitat usage, which could promote microgeographic separation between species, thereby facilitating species coexistence. We find evidence that species abundance depends on factors that govern water distribution within the intertidal (e.g., tidal inundation, precipitation, topography), all of which are moderated by climatic and marine variables. Furthermore, our results align with species-specific life history and physiological tolerances of all five community members. Integrating community member abundance into the model indicated that rivulus and F. confluentus occupy similar microhabitats, and that rivulus can be excluded from its preferred habitat by F. confluentus. Our data indicate that complex intertidal habitat community structure is driven by differences in microhabitat usage, while individual species abundance is dictated by inundation and environmental mediators. Furthermore, species with similar ecology (rivulus, F. confluentus) compete for the use of microhabitats.
