Do effects of landscape factors on coastal pond macrophyte communities depend on species traits?

Abstract

We investigated the richness and composition of aquatic macrophyte communities of non-fragmented ponds in a matrix of coastal dunes in Southern Brazil. We tested three hypotheses on natural wetlands: (1) area, diversity of habitats and hydroperiod increase the total macrophyte richness; (2) isolation among ponds decreases the total macrophyte richness; and (3) the influence of environmental factors on macrophyte richness and composition change among macrophyte groups with different degrees of tolerance to hydrological variation. Our results showed that area was not a determining factor for macrophyte richness in coastal dune ponds. Diversity of habitats positively influenced total macrophyte richness, both hydrophyte and emergent species. Total richness of macrophytes declined with the increase in distance from source areas. However, this pattern varied among the study macrophyte groups with different degree of tolerance to hydrological variations. Whereas richness of hydrophyte and emergent species richness were related with isolation, the richness of amphibious species was not. Species composition was determined by the combination of the following environmental factors: isolation, diversity of habitats and hydroperiod. The current process of fragmentation taking place in Southern Brazil will increase the isolation among wetlands, and will influence the aquatic macrophyte species. The isolation effects may be most severe for hydrophytes.