Vegetation of South Padre Island, Texas: Freshwater and Brackish Wetlands (Report‪)‬

Abstract.--Species composition and importance, species richness, species diversity, and evenness were compared among 14 freshwater and brackish wetlands in the secondary dunes and vegetated flats topographic zone of South Padre Island, Texas. Twenty-four different species were found among the sites, but the greatest species richness at a site was only 14. Mean species diversity was 0.855 and mean evenness was 0.797. Both parameters showed little variability among sites. South Padre Island wetlands had significantly lower species richness and species diversity than freshwater and brackish marshes of the adjacent Texas mainland. Conversely, evenness was similar among island and mainland wetlands. Most of the island wetlands shared 62% to 67% of their species and similarity in species composition was significantly greater for island wetlands than mainland wetlands. Bulrush (Schoenoplectus pungens) was the dominant species at nine wetlands. Umbrella grass (Fuirena simplex) and marshhay cordgrass (Spartina patens) each were dominant in two wetlands. Bushy bluestem (Andropogon glomeratus) was dominant in one wetland. The meager data currently available suggests that species richness of wetland communities is similar on northern and southern portions of Padre Island, but similarity in species composition is modest. Species importance in wetland communities varies markedly between northern and southern areas of Padre Island. **********