Using environmental effects on fecundity to compare the adaptive characteristics of the morphs in a hybrid zone of Littorina saxatilis
- Cite this article as:
- Cruz, R. & Garcia, C. Evolutionary Ecology (2003) 17: 157. doi:10.1023/A:1023038817912
We studied the role of ecological processes in the maintenance of a hybrid zone for the intertidal snail Littorina saxatilis by comparing the fecundity responses of the females from different morphs to local environmental variation. This procedure makes it possible to discern if the environments maximizing fecundity are the same in these morphs, and therefore to study adaptive differences between them. We found that the pure morphs were adapted to their respective shore levels, thus confirming that this hybrid zone is associated with the occurrence of an ecotone between two habitats. However, fecundity differences did not explain the precise spatial location and width of the hybrid zone. We also found that the adaptive characteristics of hybrids were very different from those of the pure morphs, in sharp contrast with any expectations based on their intermediate phenotype. The comparison of fitness responses to environmental variation might be an useful procedure in the field study of adaptive differences between groups of individuals.