Neither slugs nor snails: a molecular reappraisal of the gastropod family Velutinidae

The systematics of the marine mollusc family Velutinidae has long been neglected by taxonomists, mainly because their often internal and fragile shells offer no morphological characters. Velutinids are usually undersampled owing to their cryptic mantle coloration on the solitary, social or colonial ascidians on which they feed and lay eggs. In this study, we address the worldwide diversity and phylogeny of Velutinidae based on the largest molecular dataset (313 specimens) to date, accounting for > 50% of the currently accepted genera, coupled with morphological and ecological data. Velutinids emerge as a diverse group, encompassing four independent subfamily-level lineages, two of which are newly described herein: Marseniopsinae subfam. nov. and Hainotinae subfam. nov. High diversity was found at genus and species levels, with two newly described genera (Variolipallium gen. nov. and Pacifica gen. nov.) and ≥ 86 species in the assayed dataset, 58 of which are new to science (67%). Velutinidae show a remarkable morphological plasticity in shell morphology, mantle extension and chromatic patterns. This variability is likely to be the result of different selective forces, including habitat, depth and trophic interactions

Spicy food for the egg-cowries: the evolution of corallivory in the Ovulidae (Gastropoda: Cypraeoidea)

IntroductionHost-parasite associations provide very useful models to study adaptive processes. We investigated the interaction between carnivorous marine gastropods, the Ovulidae or egg-cowries, and their cnidarian food targets. Ovulidae (Fleming, 1828), is a family of specialized carnivorous caenogastropods that feed by browsing on octocorals (Anthozoa: Octocorallia: Malacalcyonacea and Scleralcyonacea) or, to a much lesser degree, on antipatharians (Anthozoa: Hexacorallia: Antipatharia) and Stylasteridae (Hydrozoa: Hydroidolina: Anthoathecata). Very scanty information is available on the phylogenetic relationships and the degree of specificity of the relationship with the cnidarians of this corallivorous lineage, especially for deep-water taxa.MethodsTo assess taxonomic identifications and investigate cnidarian/ovulid relationships in the context of their evolution, we generated an extensive molecular dataset comprising two mitochondrial (cox1 and 16S rDNA) and one nuclear gene (28S rDNA) from 524 specimens collected worldwide. The coral hosts of the ovulid species have been identified by integrating literature data with new records, employing morphological and/or molecular (the mitochondrial 16S rDNA and mtMSH, and the nuclear ITS2) markers.ResultsWe obtained a molecular phylogenetic framework for the Ovulidae, time-calibrated with nine reliable fossil records. An ancestral state reconstruction allowed to identify Hexacorallia or Hydroidolina as the most likely ancestral cnidarian host for the Ovulidae.DiscussionOur phylogenetic hypothesis revealed the existence of groups that do not completely correspond to the currently employed subfamilial arrangement. Concerning trophic ecology, while only pediculariines (Pedicularia and allied) are associated with hydrozoans (Stylasteridae), our results suggest that some ovulid lineages shifted independently between octocorals and hexacorals

First molecular phylogeny of the circumtropical bivalve family Pinnidae (Mollusca, Bivalvia): Evidence for high levels of cryptic species diversity

The family Pinnidae Leach, 1819, includes approximately 50 species of large subtidal and coastal marine bivalves. These commercially important species occur in tropical and temperate waters around the world and are most frequently found in seagrass meadows. The taxonomy of the family has been revised a number of times since the early 20th Century, the most recent revision recognizing 55 species distributed in three genera: Pinna, Atrina and Streptopinna, the latter being monotypic. However, to date no phylogenetic analysis of the family has been conducted using morphological or molecular data. The present study analyzed 306 pinnid specimens from around the world, comprising the three described genera and ca. 25 morphospecies. We sequenced the mitochondrial genes 16S rRNA and cytochrome coxidase subunit I, and the nuclear ribosomal genes 18S rRNA and 28S rRNA. Phylogenetic analysis of the data revealed monophyly of the genus Atrina but also that the genus Streptopinna is nested within Pinna. Based on the strong support for this relationship we propose a new status for Streptopinna Martens, 1880 and treat it as a subgenus (status nov.)of Pinna Linnaeus, 1758. The phylogeny and the species delimitation analyses suggest the presence of cryptic species in many morphospecies displaying a wide Indo-Pacific distribution, including Pinna muricata, Atrina assimilis, A. exusta and P. (Streptopinna) saccata but also in the Atlantic species A. rigida. Altogether our results highlight the challenges associated with morphological identifications in Pinnidae due to the presence of both phenotypic plasticity and morphological stasis and reveal that many pinnid species are not as widely distributed as previously thought.Organismic and Evolutionary Biolog

Data from: Delimiting species of marine gastropods (Turridae, Conoidea) using RAD-sequencing in an integrative taxonomy framework

Species delimitation in poorly-known and diverse taxa is usually performed based on monolocus, DNA barcoding-like approaches, while multilocus data are often used to test alternative species hypotheses in well-studied groups. We combined both approaches to delimit species in the Xenuroturris / Iotyrris complex, a group of venomous marine gastropods from the Indo-Pacific. First, COI sequences were analyzed using three methods of species delimitation, ABGD, PTP and GMYC to propose primary species hypotheses (PSH). Second, RAD-seq data were also obtained and an IQ-tree phylogenetic tree produced. We tested the impact of the level of missing data on the robustness of the phylogenetic tree obtained with the RAD-seq data. Alternative species partitions revealed with the COI dataset were also tested using the RAD-seq data and the BFD method. The congruence between the species hypotheses proposed with the mitochondrial gene and the clades in the RAD-seq tree, together with the morphological variability of the shell and the radula and the distribution pattern, was used to turn the PSH into secondary species hypotheses (SSH). Allopatric PSH defined with the COI gene were interpreted to correspond to intraspecific structure. Most of the species are found sympatrically in the Philippines, and only one is confidently identified as a new species and described as Iotyrris conotaxis n. sp. The results obtained demonstrate the efficiency of the combined monolocus/multilocus approach to delimit species

COI and RAD-seq trees

MrBayes, BEAST and RAxML trees for COI; RaxML trees for the RAD seq dataset, with the loci shared by at least 30, 40, 50, 60, 70, 80% of the samples

High cryptic diversity in the kleptoparasitic genus Hyalorisia Dall, 1889 (Littorinimorpha: Capulidae) with the description of nine new species from the Indo-West Pacific

Species in the family Capulidae (Littorinimorpha: Capuloidea) display a wide range of shell morphologies. Several species are known to live in association with other benthic invertebrates—mostly bivalves and sabellid worms, but also other gastropods—and are believed to be kleptoparasitic filter feeders that take advantage of the water current produced by the host. This peculiar trophic ecology, implying a sedentary lifestyle, has resulted in highly convergent shell forms. This is particularly true for the genus Hyalorisia Dall, 1889, which occurs in deep water in the Caribbean and Indo-West Pacific provinces, with two nominal species recognized so far. Combining morphological, ecological and molecular data, we assessed the diversity of the genus, its phylogenetic position inside the family and its association with its bivalve host, the genus Propeamussium de Gregorio, 1884 (Pectinoidea), resulting in the description of nine new cryptic species. When sympatric, species of Hyalorisia are associated with different host species, but the same species of Propeamussium may be the host of several allopatric species of Hyalorisia

Mapping the missing branch on the neogastropod tree of life: molecular phylogeny of marginelliform gastropods

Marginelliform gastropods are a heterogeneous and diverse group of molluscs encompassing over 1,600 living species, among which are the smallest known neogastropods. The relationships of marginelliform gastropods within the order Neogastropoda are controversial, and the monophyly of the two marginelliform families the Marginellidae(J. Fleming, 1828 and the Cystiscidae Stimpson, 1865, remains unconfirmed. DNA sequence data have never been used to assess the relationships of the marginelliform gastropods, making this group the only major branch missing in our current understanding of the neogastropod tree of life. Here we report results of the first multilocus phylogenetic analysis of marginelliform gastropods, which is based on a dataset comprising 63 species (20 genera) of Marginellidae and Cystiscidae, and a wide range of neogastropod lineages. The Marginellidae and Cystiscidae form a moderately supported Glade that is sister to the family Volutidae. Marginellona gigas appears to be sister to all other marginelliforms. The subfamily Marginellinae was recovered as a well-supported Glade, and good resolution of this part of the tree makes it possible to propose amendments to the family-level classification of the group. The relationship between Granulina and other marginelliforms could not be resolved and requires further study. Due to poor resolution of basal relationships within the Marginellidae Cystiscidae Glade, the monophyly of the Cystiscidae was neither confirmed nor convincingly rejected. The shell morphology of most marginellid and cystiscid genera is taxonomically not very informative but, nevertheless, of the traditionally recognized genera only Gibberula and Dentimargo were shown to be polyphyletic. Although a comprehensive systematic revision of the group requires more extensive taxonomic sampling (e.g. with better representation of the type species of nominal genus -group names), our results support the superfamily Volutoidea, comprising four families (Volutidae, Cystiscidae, Marginellidae and Marginellonidae), with the placement of the Granulinidae uncertain for the time being

Radseq raw data (demultiplexed fastq)

This file will be a zip file containing the demultiplexed raw reads for each sample. The un-assigned reads (no barcode identified) are not included. They are available on request

Data from: Delimiting species of marine gastropods (Turridae, Conoidea) using RAD-sequencing in an integrative taxonomy framework

Species delimitation in poorly-known and diverse taxa is usually performed based on monolocus, DNA barcoding-like approaches, while multilocus data are often used to test alternative species hypotheses in well-studied groups. We combined both approaches to delimit species in the Xenuroturris / Iotyrris complex, a group of venomous marine gastropods from the Indo-Pacific. First, COI sequences were analyzed using three methods of species delimitation, ABGD, PTP and GMYC to propose primary species hypotheses (PSH). Second, RAD-seq data were also obtained and an IQ-tree phylogenetic tree produced. We tested the impact of the level of missing data on the robustness of the phylogenetic tree obtained with the RAD-seq data. Alternative species partitions revealed with the COI dataset were also tested using the RAD-seq data and the BFD method. The congruence between the species hypotheses proposed with the mitochondrial gene and the clades in the RAD-seq tree, together with the morphological variability of the shell and the radula and the distribution pattern, was used to turn the PSH into secondary species hypotheses (SSH). Allopatric PSH defined with the COI gene were interpreted to correspond to intraspecific structure. Most of the species are found sympatrically in the Philippines, and only one is confidently identified as a new species and described as Iotyrris conotaxis n. sp. The results obtained demonstrate the efficiency of the combined monolocus/multilocus approach to delimit species

An Antarctic flock under the Thorson's rule: Diversity and larval development of Antarctic Velutinidae (Mollusca: Gastropoda)

In most marine gastropods, the duration of the larval phase is a key feature, strongly influencing species distribution and persistence. Antarctic lineages, in agreement with Thorson's rule, generally show a short pelagic developmental phase (or lack it completely), with very few exceptions. Among them is the ascidian-feeding gastropod family Velutinidae, a quite understudied group. Based on a multilocus (COI, 16S, 28S and ITS2) dataset for 182 specimens collected in Antarctica and other regions worldwide, we investigated the actual Antarctic velutinid diversity, inferred their larval development, tested species genetic connectivity and produced a first phylogenetic framework of the family. We identified 15 Antarctic Molecular Operational Taxonomic Units (MOTUs), some of which represented undescribed species, which show two different types of larval shell, indicating different duration of the Pelagic Larval Phase (PLD). Antarctic velutinids stand as an independent lineage, sister to the rest of the family, with extensive hidden diversity likely produced by rapid radiation. Our phylogenetic framework indicates that this Antarctic flock underwent repeated events of pelagic phase shortening, in agreement with Thorson's rule, yielding species with restricted geographic ranges