MORPHOLOGICAL AND GENETIC ANALYSIS OF TWO SYMPATRIC MORPHS OF THE DOGWHELK NUCELLA LAPILLUS (GASTROPODA: MURICIDAE) FROM GALICIA (NORTHWESTERN SPAIN)

Abstract

There are two morphs, exposed and sheltered, of the dogwhelk Nucella lapillus associated with different degrees of exposure on the rocky shores of Galicia (northwestern Spain). These two morphs are typically found at different localities (allopatrically), but in a few sites they can be found in sympatry. We have analysed the shell and radular characteristics of these two morphs from a locality where they appear in sympatry. Genetic analysis using microsatellites was also performed. Morphological analysis was applied to shelled embryos, juveniles and adults. The results indicate consistent morphological differentiation across life‐history stages, suggesting genetic determination. Differentiation in radular morphology (width of the rachidian teeth) was also detected in adults. Other taxonomically relevant traits such as protoconch morphology did not show differences between morphs. These results agree with the intraspecific polymorphism found in this species in other parts of Europe, hence the two morphs may represent ecotypes adapted to contrasted habitats. Although the relative contributions of classical genetic variation and phenotypic plasticity to variation in shell morphology remains unknown, our observations of genetic differentiation between the two morphs indicate that the genetic component is significant.