Metacommunity structure of estuarine fish larvae: The role of regional and local processes

Understanding the effects of regional processes on local community structure is a central issue of metacommunity studies. Here we examined the relative contribution of both regional and local processes to fish larvae community structure of seven brackish lagoons located along the Mexican Atlantic coast. The database analysed includes over 982 sampling stations. Partial Mantel tests were used to determine whether among lagoon differences in species composition were related to local, and/or regional-scale factors while controlling the effects of both geographical distances and lagoon environmental characteristics. Results indicate that regional processes had significant (P < 0.05) influence on the composition of the ichthyoplankton communities, with environmental characteristics either included (r² = 19.5) or removed (r² = 23.7), whereas local environmental characteristics were non-significantly associated (P = 0.917). Alongshore currents associated with larval duration appeared to be an important factor affecting connectivity among estuaries, whereas offshore currents seemed to represent an ecological boundary between the southern Gulf of Mexico and the Yucatán coasts. Also, regional terrestrial changes in freshwater sources between these regions appeared to be determinant for the presence of certain species. Metacommunity structure of the lagoons agrees with the "mass effects" model, in which patches are heterogeneous and regional phenomena represent the crucial spatial scales in community dynamics. There is an increasing need to model larval behaviour in relation to the physical scenario to evaluate the role of alongshore currents and oceanographic boundaries as they affect the extent of larval dispersal.