FIDDLER CRAB-VEGETATION INTERACTIONS IN HYPERSALINE HABITATS

Abiotic conditions often change ecological interactions. Studies in ar eas with low to moderate soil salinities have demonstrated a facultati ve mutualism between fiddler crabs and salt marsh vegetation. In these habitats, fiddler crab burrowing increases plant growth, and plant ro ots help support the walls of crab burrows. We looked for these intera ctions in hypersaline soils bordering unvegetated salt pans in a Georg ia salt marsh. Crab burrows and vegetation cover were positively assoc iated. Neither crab removals nor burrow additions demonstrated a posit ive effect of crabs on vegetation. However, both vegetation removals a nd the addition of an artificial canopy (suspended shadecloth) demonst rated a strong positive effect of vegetation on crab burrows. In contr ast to previous studies, we found no evidence that plants supported bu rrow walls. Instead, crabs likely associate with vegetation to avoid p redators. Our results caution against extrapolating experimental resul ts between habitats with different abiotic conditions. (C) 1998 Elsevi er Science B.V.