Document: DAN-3-50-2

Effects of tidal inundation on the distribution of wolf spiders in an intertidal salt marsh.

LEWIS, D.* and R.F.DENNO

University of Maryland, College Park, MD, U.S.A. ¹

Abstract:
The wolf spider Pardosa littoralis is an important predator of herbivorous insects in salt marshes along the atlantic coast of the United States. Previous studies have shown that wolf spider density decreases with decreasing marsh elevation, contributing to outbreaks of the planthopper Prokelisia marginata, its primary prey in low marsh habitats. Habitat structure also changes with marsh elevation. Vegetation in the low marsh is taller with culms more widely spaced than grass at higher elevations. Thatch is absent from the low marsh but increases with elevation. This study tested whether tidal inundation and vegetation structure contribute to the rarity of wolf spiders in the low marsh. Spider response to incoming tides was tested in floodable microcosms configured as an inclined plane to simulate high and low marsh habitats with and without thatch. In a typical low marsh habitat without thatch, inundation forced roughly half the released spiders to emigrate from the "low-marsh habitat" for higher ground. Adding thatch to the "low-marsh habitat" enhances the retention of some spiders in this habitat because they gain refuge from rising tides by climbing grass culms. Virtually all spiders remained in the simulated high-marsh habitat as tidewaters rose. These results are consistent with the view that frequent tidal inundation tends to selectively uncouple predator-prey interactions in low-marsh habitats and promote planthopper outbreaks there.

Keywords: Tidal inundation, Wolf spider, predator-prey coupling

This abstract is being presented at: 1:00 PM in session:
Oral Session #65: Wetlands, Estuaries and Salt Marshes.