Molecular and morphometric data suggest the presence of a neglected species in the marine gastropod family Conidae

Abstract

Knowledge concerning the taxonomic diversity of marine organisms is crucial for understanding processes associated with species diversification in geographic areas that are devoid of obvious barriers to dispersal. The marine gastropod family Conidae contains many species complexes due to lack of clear morphological distinctiveness and existence of morphological intergradations among described species. Conus flavidus Lamarck, 1810 and Conus frigidus Reeve, 1848 are currently recognized as distinct taxa, but are often difficult to distinguish by morphological characters and include several synonyms, including Conus peasei Brazier, 1877. C. peasei was originally described by Pease in 1861 (as Conus neglectus) based on slight morphological differences of a population of C. flavidus from Hawaii that distinguished it from C. flavidus from elsewhere. To evaluate the systematics of this group and specifically test the hypothesis of synonymy of C. peasei with C. flavidus, we examined molecular and morphometric data from specimens of C. flavidus, C. frigidus and C. peasei (i.e., C. flavidus from Hawaii). Multiple clades that contain individuals from particular geographic regions are apparent in gene trees constructed from sequences of a mitochondrial gene region. In particular, sequences of C. peasei cluster together separately from sequences of C. flavidus and C. frigidus. Although individuals of C. peasei, C. flavidus and C. frigidus each contain a unique set of alleles for a nuclear locus, a conotoxin gene, alleles of C. peasei are more similar to those of C. flavidus. In addition, sequences of a region of a second nuclear gene are identical among C. peasei and C. flavidus though they are distinct from sequences of C. frigidus. Morphometric data revealed that shells of C. peasei are distinct in some aspects, but are more similar to those of C. flavidus than to those of C. frigidus. Taken together, these results suggest that C. peasei represents a distinct species. Moreover, based on the contradictory relationships inferred from the mitochondrial and nuclear sequences (as well as morphometric data), C. peasei may have originated through past hybridization among the ancestral lineages that gave rise to C. flavidus and C. frigidus.