An Interpretation of the Taxonomic Relationship Between the LimpetsPatella Rusticaand P.Piperata

Abstract

The taxonomic relationship between the limpetsPatella rustica(Mollusca: Archaeogastropoda) andP. piperatais unclear with controversy as to whetherP. piperatashould be given specific status. The problems stem from its similar morphology but different biogeographic range fromP. rustica. Individuals from seven populations ofP. rusticaand three ofP. piperatawere analysed for a combination of morphological and genetical characters. Morphological analyses of shell shape and radular morphology revealed differences between species for radular length, higher inP. rusticathan inP. piperata, and the shape of the pluricuspid teeth of the radula with a well-developed internal cusp inP. piperatabut not inP. rustica. Electrophoretic results based on 11 allozyme loci, however, did not distinguish the two species clearly. The overall genetic identity value between the two was 0·861, a value which lies within the range for conspecific populations of other patellids. It is proposed thatP. piperataon the basis of the genetic data obtained, may represent a subspecies ofP. rusticathat is in the process of diverging due to its geographic isolation.