Morphological Differences and Low Dispersal Between Local Populations of the Tropical Beach Isopod, Excirolana Braziliensis
Abstract:Absence of a larval dispersal stage may cause some marine species to have greater population subdivision than those with larval dispersal. Specimens of the brooding isopod Excirolana braziliensis, collected between 1969–1986 from three Panamanian beaches, were analyzed to estimate whether local populations differed and whether distance between beaches was correlated with interbeach dispersal. Two beaches are in the Pacific Ocean, while the third is in the Caribbean Sea. All are near the entrance to the Panama Canal, which connects the two oceans. Morphology of specimens from all three beaches was significantly different, and these differences persisted between seasons and over years. In contrast, there was no significant morphological variation within local populations due to sex, date or location. Out of 211 mature specimens examined, only three (1.4%) were identified as morphological outliers which had probably dispersed from another beach to the one they were collected on. In addition to comparing specimens collected from the field with each other, we cultured each local population in the laboratory and obtained evidence that the morphological differences were inherited. The results support the hypothesis that a species whose life history does not include a larval dispersal stage can have a strongly subdivided population.
Document Type: Research Article
Publication date: 1988-03-01
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