title: Family matters: The first molecular phylogeny of the Onchidorididae Gray, 1827 (Mollusca, Gastropoda, Nudibranchia).
abstract: Recent investigations into the evolution of the Onchidorididae using morphological based methods have resulted in low support for relationships among genera. This study aims to determine if molecular data corroborates recent morphological interpretations of the evolution of Onchidorididae. Five genetic markers: 16S, 18S, 28S, cytochrome c oxidase 1 (COI) and histone 3 (H3), were sequenced from 32 species comprising Onchidorididae and five other families, three from Phanerobranchia and two from Cryptobranchia. Phylogenies were estimated using maximum likelihood, and Bayesian inference analyses; with both yielding similar topologies. Molecular analyses resulted in high support for the monophyly of the suctorian clade and the placement of the genera within Onchidorididae. However, the Onchidorididae forms a paraphyletic grouping due to the recovery of the Goniodorididae and the Akiodorididae nested within family. In addition, the placement of Corambe as the most derived member of Onchidorididae is contradicted by the present study. Rather it is sister to a large clade that includes Acanthodoris and the species traditionally placed in Onchidoris and Adalaria, now defined as Onchidorididae. We have chosen to maintain Corambidae as a distinct taxon (including Corambe and Loy), sister to Onchidorididae. We also maintain Goniodorididae, Akiodorididae and Calycidoridae (including Calycidoris and Diaphorodoris), which along with the Onchidorididae and Corambidae comprise the suctorian superfamily Onchidoridoidea. Ancestral character reconstruction also suggests that the formation of a gill pocket, a character that currently defines the Cryptobranchia, may have evolved multiple times from an ancestor that lacked the ability to retract its gills into a fully formed gill pocket. The diversity of gill morphology displayed by the Onchidoridoidea will help give new insight into the evolution of this complex character within the Nudibranchia.
authors.affiliation: Department of Invertebrate Zoology and Geology, California Academy of Sciences, 55 Music Concourse Dr., Golden Gate Park, San Francisco, CA 94118, United States; Department of Biology, San Francisco State University, 1600 Holloway Dr., San Francisco, CA 94132, United States. Electronic address: jhallas@calacademy.org.
authors.forename: Joshua M
authors.initials: JM
authors.lastname: Hallas
authors.affiliation: Department of Invertebrate Zoology and Geology, California Academy of Sciences, 55 Music Concourse Dr., Golden Gate Park, San Francisco, CA 94118, United States.
authors.forename: Terrence M
authors.initials: TM
authors.lastname: Gosliner
mesh_terms: D000818:Animals; D001499:Bayes Theorem; D005075:Biological Evolution; D005260:Female; D049851:Gastropoda / Q000033:anatomy & histology / Q000145:classification* / Q000235:genetics; D005836:Genitalia, Female / Q000033:anatomy & histology; D005880:Gills / Q000033:anatomy & histology; D010802:Phylogeny; D017422:Sequence Analysis, DNA
keywords: Ancestral character state reconstruction; Gill evolution; Morphological evolution; Phylogenetics; Sea slug