Seasonal abundance and diversity of spiders in two intertidal marsh plant communities

The spiders of two Mississippi marsh communities were studied from January 1982 through March 1983. Monthly collections were made in two adjacent marsh plant zones dominated bySpartina cynosuroides (L.) Roth andJuncus roemerianus Scheele respectively. A total of 38 species of spiders (36 inSpartina, 33 inJuncus) representing 13 families were collected. The dominant species in theSpartina zone includedPirata mayaca Gertsch,Lycosa watsoni Gertsch (Lycosidae),Clubiona saltitans Emerton,Scotinella formica (Banks) (Clubionidae),Floricormus sp. (Linyphiidae),Dictyna sylvania Chamberlin & Ivie (Dictynidae),Paramaevia hobbsae (Barnes) (Salticidae), andAgelenopsis barrowsi Gertsch (Agelenidae). The dominant species in theJuncus zone includedLycosa watsoni, Pirata mayaca, Clubiona saltitans andSarinda hentzi (Banks) (Salticidae). Density, biomass, species richness and equitability peaked in May in theJuncus zone and in June in theSpartina zone. Peak levels of density and biomass corresponded to the reproductive activity of the common species, while diversity patterns were attributable to the reproductive activity of the less common species. Mean values of density and biomass over the study period were 84.8 spiders per m² and 155.6 mg per m² in theSpartina zone and 39.4 spiders per m² and 133.0 mg per m² inJuncus zone. The Juncus zone was flooded more frequently, contained less litter, and supported lower overall density and diversity of spiders.