Phylogenetic position and morphological descriptions of Chiton species from the south-eastern Pacific

In the south-eastern Pacific Ocean (SEP), six species of the genus Chiton have been recorded. However, the taxonomic status and geographic distribution of some of these species is controversial. In this study, we compare and describe Chiton species in the SEP. More than 3000 specimens of six species from 49 localities were analysed for morphological features. Among these, 27 specimens of the six species from the SEP were sequenced for the mitochondrial barcode region (COI) and ribosomal 16S and 18S to infer phylogenetic relationships. Phylogenetic reconstruction indicates that the genus Chiton in the SEP represents a polyphyletic group and confirms the placement of C. barnesii in Chiton and not in Radsia, as previously suggested. Among Chiton s.s., C. cumingsii is the sister-species of C. magnificus, while C. granosus is a sister-species of C. barnesii. This analysis also indicates that C. bowenii is a junior synonym of C. magnificus. Our results improved the knowledge of systematics and distribution of Chiton species in the SEP, suggesting the presence of five valid species of the genus. In this study, we designate a lectotype for C. cumingsii and a neotype for C. granosus.

Automated summary

This study compares and describes Chiton species in the south-eastern Pacific Ocean, revealing a polyphyletic group in the SEP. The research confirms the presence of five valid species in the region and designates lectotypes for C. cumingsii and neotypes for C. granosus.