Environmental filtering and plant functional types on Mexican foredunes along the Gulf of Mexico

Ecological theory suggests that environmental filtering (the survival or elimination of species in the community in response to environmental constraints) is a key process in the species assemblages of communities. Environmental filters, such as sand movement and soil salinity in coastal dunes and beaches, may result in shared ecological tolerances and functional types, independently of phylogenetic and evolutionary history. In 19 beach-foredune sites located along the coast of the Gulf of Mexico we studied plant functional composition and diversity of vascular plants. Functional groups were determined with a classification analysis. Relative importance values and diversity indices of species and functional groups were compared with ANOVA tests. We distinguished 5 groups: a group of species tolerant to soil salinity and burial, most abundant on accreting beaches; a group of species tolerant only to burial, which were abundant on all coasts; and 3 groups that lacked specific responses to burial and soil salinity and were most abundant on stable and erosive coasts. Accreting foredunes showed the lowest species richness and functional diversity, because only a few species were tolerant to burial and soil salinity. In the foredune environment, sediment dynamics and geomorphological processes act as environmental filters that largely determine the floristic and functional composition of the community.