The dispersal potential of benthic macroinvertebrates is influenced by factors acting at small spatial scales in tropical estuaries.

This study aimed to assess the dispersal patterns of macroinvertebrates at local and regional scales within typical tropical and semi-arid estuaries during periods of high and low rainfall. To analyze the dispersal potential of polychaete and mollusk communities, we considered four functional traits, categorized into 14 groups: larval development, fecundity, body size, and mobility. Diversity partitioning revealed that both typical tropical and semi-arid tropical estuaries showed a consistent trend of high functional alpha diversity across sampling periods. However, upon analyzing the influence of environmental variables and spatial factors (distance between sites using geographic coordinates) on functional dispersal categories, we found a difference between the two. The spatially structured environment influenced the functional diversity of communities in typical tropical estuaries during the sampling period. This occurred because of a clear longitudinal salinity gradient, making neighboring regions more similar and suitable for functionally similar taxa. In contrast, the semi-arid estuaries showed differences across the sampling periods in the relationship between environmental and/or spatial factors and potentially dispersal-related traits, demonstrating that temporal changes influenced the dispersal dynamics of the organisms. Therefore, the occurrence and distribution of potentially dispersal-related functional categories in estuaries are influenced more by environmental factors acting at smaller spatial scales. [ABSTRACT FROM AUTHOR]