Quantifying edge effects on apple snails (Pomacea paludosa) and their eggs at the junction of two wetland habitat types

Abstract

Plant community structure and the creation of ecotones from the juxtaposition of distinct habitats influence gastropod distribution, abundance and species diversity. However, the influence of edge effects associated with ecotones May be influenced by scale and sampling issues. In Florida’s Everglades, a common ecotone exists between dense sawgrass (Cladium jamaicense) and less-dense wet prairie habitats dominated by lower profile sedges and grasses. Previous studies indicate that Florida apple snails (Pomacea paludosa) concentrate their eggs along ecotones and that they appear to favour sawgrass for oviposition. However, snail densities along the ecotone have not been reported and total egg production at the landscape level has not been considered. Egg-cluster densities were greater along the sawgrass ecotone; however, total egg production in wet prairie (egg density multiplied by total area) was greater than in the sawgrass ecotone. Greater egg-cluster density along the sawgrass ecotone May be a result of increased stem encounter rates by female snails. We found that snail densities were not significantly different between sawgrass ecotone and adjacent prairie habitats in the Everglades. The results of our study, combined with observations from previous reports, indicate that the importance of edge effects on apple snails depends on the spatial scale and the particular landscape being considered. Changes in plant community structure resulting from changes in hydrology caused by wetland restoration May impact recruitment of apple snails and, ultimately, those species that prey upon them.