Appendix A. Taxonomic status of the marine gastropod Nucella canaliculata.
Dr. Jim McLean (Natural History Museum of Los Angeles County, California, USA) has recently proposed renaming this species Nucella analoga (McLean 2006, 2007). This taxonomic change is based on the hypothesis that the species currently named Nucella canaliculata represents a complex of two species. Under this scenario, Nucella canaliculata would be recognized as a northern species found from the Aleutian Islands, Alaska, USA, to Puget Sound, Washington, USA. The populations that we have studied in California and Oregon would all belong to a different species, Nucella analoga, ranging from California to Prince William Sound, Alaska. The hypothesis for a two species complex is based exclusively on shell morphology and habitat differences (with the southern species occupying more wave-exposed shores than the hypothesized northern species). The key morphological features used to differentiate the two hypothesized species are that the northern group is characterized by more prominent primary cords and deeply channeled interspaces (McLean 2006, 2007). We have observed that these morphological traits can vary within a population, and sometimes even within offspring produced by the same parents (Fig. A1). Given this morphological variation, we agree with McLean (2006) that molecular data are needed to fully evaluate the hypothesis that the Nucella canaliculata complex contains two species. Until this hypothesis can be addressed, we have retained the original species name Nucella canaliculata in this paper. Note that if McLean's hypothesis is confirmed, all of the populations that we have studied in California and Oregon would still belong to a single species (renamed N. analoga).
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| FIG. A1. Two full-sibling, F2 generation snails produced in our laboratory experiments (see Materials and Methods) by a breeding couple that originated from Van Damme State Park, California, USA. Both snails hatched from the same cluster of egg capsules and were raised simultaneously under identical conditions within the same 1-L container. The individual on the left lacks prominent primary cords and deeply channeled interspaces and would be classified as Nucella analoga (McLean 2007), whereas its sibling on the right possesses these features and presumably would be classified as Nucella canaliculata. Scale bar = 2 cm. |
LITERATURE CITED
McLean, J. H. 2006. Hypothesis for the recognition of Nucella analoga (Forbes, 1852) in the northeastern Pacific. The Festivus 38(2):17–21.
McLean, J. H. 2007. Gastropoda: Shelled Gastropoda. Pages 713–753 in J. T. Carlton, editor. The Light and Smith Manual: Intertidal Invertebrates from Central California to Oregon. University of California Press, Berkeley, California, USA.