ARE SHELL SHAPES SUFFICIENT IN DETERMINING SPECIES?

Many species are identifiable by visible external morphology. These distinguishing features are often used as a proxy for genetic differences among studied taxa. This is true for most gastropods, which are traditionally recognized and identified by conchological characters, as the shell is most readily preserved. However, shell shape can be highly variable depending on the species, and there are rare examples where the concordance between shell morphology and genetic differences are evaluated.

Using extant East Pacific Littorina species from the west coast of North America (the sister species pair L. plena and L. scutulata; L. keenae), this study evaluates the consistency of shell shape for each species, and combines this with genetic difference measures. Though the amount of shell shape variation is species dependent, we expect that shell shape does reflect underlying genetic differences. Shell shapes of these species are compared using modern specimens, Pleistocene fossils, and with an extinct species (†L. petricola), to additionally assess the variability of Littorina shell shape over time.