Differences in dispersal of an intertidal gastropod in two habitats: the need for and design of repeated experimental transplantation

Applying general ecological models to new habitats is made difficult where ecological processes vary from one habitat to another. To improve the gener ality of such models and the precision of predictions made from them, it is necessary to understand the processes that prevent generalizations. The be haviour of intertidal gastropods (Bembicium auratum) varies from rocky shor es to mangrove forests near Sydney (Australia) and creates a barrier to gen eralization of models from one habitat to the other. Differences in behavio ur could result from intrinsic differences in the populations of Bembicium occupying the different habitats or from responses to extrinsic cues that v ary from habitat to habitat or from a combination of these factors. To test hypotheses from these three models, Bembicium were reciprocally transplant ed between the habitats and their subsequent behaviour was compared to that of controls. Outcomes of the experiment varied considerably in space and t ime, but there was no evidence of intrinsic differences between populations of snails in the two habitats. Some results suggested that a combination o f intrinsic and extrinsic factors causes the observed differences in behavi our. Most results were consistent with the model that differences in behavi our of snails on rocky shores and from that shown in mangrove forests are c aused by differences between the two habitats and not the snails. The behav iour of individual Bembicium was extremely plastic and changed rapidly on a rrival in a new habitat. Experiments of this type are an effective tool for investigating variation in behavioural processes. The study demonstrated t hat behavioural plasticity can act as a barrier to generalizations from som e ecological models. (C) 1999 Elsevier Science B.V. All rights reserved.