ABSTRACT

Many barnacle species are difficult to distinguish because of the similarity of their arthropod characters and the high coefficient of variation in their shell features. However, electrophoresis of barnacle enzymes is proving to be a major aid in the investigation of several problems in barnacle taxonomy. In particular, some species complexes of the genus Chthamalus have been resolved and the cladistic relationships between the species established. Studies on geographic variation within species from several genera show that, in general, there is very little variation along a seaboard unless there is a physical separation of populations. The evidence for selection on enzyme phenotypes in barnacles is reviewed. A major problem in interpreting the data is that the taxonomy of many important species complexes is uncertain and it is difficult to explain results when the number of species in a sample is not known.