Patterns of Cladogenesis in the Venomous Marine Gastropod Genus Conus from the Cape Verde Islands

The role of the Sunda shelf biogeographic barrier in the cryptic differentiation of Conus litteratus (Gastropoda: Conidae) across the Indo-Pacific region

Geographical and oceanographic processes have influenced the speciation of marine organisms. Cone snails are marine mollusks that show high levels of endemism and a wide distributional range across the Indian and Pacific Oceans. Discontinuities in distributions caused by biogeographic barriers can affect genetic connectivity. Here we analysed the connectivity within Conus litteratus using samples from the Lakshadweep archipelago (Arabian Sea, Indian Ocean) and from the Pacific Ocean. Maximum likelihood analyses based on the mitochondrial cytochrome C oxidase subunit I (COI) and on the non-coding 16S ribosomal RNA (16S rRNA) genes revealed cryptic diversity within C. literatus occupying distinct oceanographic regions. The intraspecific genetic distances between the two distinct clades of C. literatus from the Arabian Sea and the Pacific Ocean ranged from 7.4% to 7.6% for COI and from 2.4% to 2.8% for 16S rRNA genes, which is larger than the threshold limit for interspecific differentiation. The haplotype network analysis also corroborated the existence of two different lineages within C. litteratus. The detected genetic discontinuities reflect the effect of the Sunda shelf biogeographic barrier on the allopatric divergence of C. litteratus.

Non-Peptidic Small Molecule Components from Cone Snail Venoms

Venomous molluscs (Superfamily Conoidea) comprise a substantial fraction of tropical marine biodiversity (>15,000 species). Prior characterization of cone snail venoms established that bioactive venom components used to capture prey, defend against predators and for competitive interactions were relatively small, structured peptides (10–35 amino acids), most with multiple disulfide crosslinks. These venom components (“conotoxins, conopeptides”) have been widely studied in many laboratories, leading to pharmaceutical agents and probes. In this review, we describe how it has recently become clear that to varying degrees, cone snail venoms also contain bioactive non-peptidic small molecule components. Since the initial discovery of genuanine as the first bioactive venom small molecule with an unprecedented structure, a broad set of cone snail venoms have been examined for non-peptidic bioactive components. In particular, a basal clade of cone snails (Stephanoconus) that prey on polychaetes produce genuanine and many other small molecules in their venoms, suggesting that this lineage may be a rich source of non-peptidic cone snail venom natural products. In contrast to standing dogma in the field that peptide and proteins are predominantly used for prey capture in cone snails, these small molecules also contribute to prey capture and push the molecular diversity of cone snails beyond peptides. The compounds so far characterized are active on neurons and thus may potentially serve as leads for neuronal diseases. Thus, in analogy to the incredible pharmacopeia resulting from studying venom peptides, these small molecules may provide a new resource of pharmacological agents.

Patterns of variation of mutation rates of mitochondrial and nuclear genes of gastropods

BACKGROUND

Although mitochondrial DNA (mtDNA) of many animals tends to mutate at higher rates than nuclear DNA (nuDNA), a recent survey of mutation rates of various animal groups found that the gastropod family Bradybaenidae (suborder Helicina) shows a nearly 40-fold difference in mutation rates of mtDNA ([Formula: see text]_m) and nuDNA ([Formula: see text]_n), while other gastropod taxa exhibit only two to five-fold differences. To determine if Bradybaenidae represents an outlier within Gastropoda, I compared estimated values of [Formula: see text]_m/[Formula: see text]_n of additional gastropod groups. In particular, I reconstructed mtDNA and nuDNA gene trees of 121 datasets that include members of various clades contained within the gastropod subclasses Caenogastropoda, Heterobranchia, Patellogastropoda, and Vetigastropoda and then used total branch length estimates of these gene trees to infer [Formula: see text]_m/[Formula: see text]_n.

RESULTS

Estimated values of [Formula: see text]_m/[Formula: see text]_n range from 1.4 to 91.9. Datasets that exhibit relatively large values of [Formula: see text]_m/[Formula: see text]_n (i.e., > 20), however, show relatively lower estimates of [Formula: see text]_n (and not elevated [Formula: see text]_m) in comparison to groups with lower values. These datasets also tend to contain sequences of recently diverged species. In addition, datasets with low levels of phylogenetic breadth (i.e., contain members of single genera or families) exhibit higher values of [Formula: see text]_m/[Formula: see text]_n than those with high levels (i.e., those that contain representatives of single superfamilies or higher taxonomic ranks).

CONCLUSIONS

Gastropods exhibit considerable variation in estimates of [Formula: see text]_m/[Formula: see text]_n. Large values of [Formula: see text]_m/[Formula: see text]_n that have been calculated for Bradybaenidae and other gastropod taxa may be overestimated due to possible sampling artifacts or processes that depress estimates of total molecular divergence of nuDNA in groups that recently diversified.

Molecular analysis reveals a cryptic species of Chthamalus (Crustacea: Cirripedia) in the Cape Verde Islands

The intertidal barnacle Chthamalus stellatus has a broad distribution, occurring in the Mediterranean, the east Atlantic shores and east Atlantic Macaronesian Islands (Madeira, the Canaries and the Azores). Traditionally, based on morphological characters, Chthamalus of the Cape Verde Islands were also regarded as C. stellatus. However, using a mitochondrial gene and two nuclear genes, we found that although Chthamalus from Cape Verde is morphologically similar to C. stellatus, there are genetic differences between the two that are larger than those found between different species of Chthamalus. We thus claim that these genetic differences justify the assignment of the Cape Verde populations as an evolutionarily significant unit and a sister clade to C. stellatus. We also show that the connection between taxonomic units that are close to each other lies not only in the resemblance between DNA sequences. We have found that numerous point mutations characterizing the Cape Verde Chthamalus are present as infrequent alleles in C. stellatus, indicating that two close taxonomic units can also share polymorphisms present in their common ancestor.

Evolutionary origin of the Atlantic Cabo Verde nibbler (Girella stuebeli), a member of a primarily Pacific Ocean family of antitropical herbivorous reef fishes

Nibblers (family Girellidae) are reef fishes that are mostly distributed in the Indo-Pacific, with one exception: Girella stuebeli, which is found in the Cabo Verde Archipelago, in the Atlantic Ocean. We capitalized on this unusual distribution to study the evolutionary history of the girellids, and determine the relationship between G. stuebeli and the remaining nibbler taxa. Based on thousands of genomic markers (RAD sequences), we identified the closest relatives of G. stuebeli as being a clade of three species endemic to the northwestern Pacific, restricted to the Sea of Japan and vicinity. This clade diverged from G. stuebeli approximately 2.2 Mya. Two alternative potential routes of migration may explain this affinity: a western route, from the Tropical Eastern Pacific and the Tropical Western Atlantic, and an eastern route via the Indian Ocean and Southern Africa. The geological history and oceanography of the regions combined with molecular data presented here, suggest that the eastern route of invasion (via the Indian Ocean and Southern Africa) is a more likely scenario.

Restructuring of the 'Macaronesia' biogeographic unit: A marine multi-taxon biogeographical approach

The Azores, Madeira, Selvagens, Canary Islands and Cabo Verde are commonly united under the term “Macaronesia”. This study investigates the coherency and validity of Macaronesia as a biogeographic unit using six marine groups with very different dispersal abilities: coastal fishes, echinoderms, gastropod molluscs, brachyuran decapod crustaceans, polychaete annelids, and macroalgae. We found no support for the current concept of Macaronesia as a coherent marine biogeographic unit. All marine groups studied suggest the exclusion of Cabo Verde from the remaining Macaronesian archipelagos and thus, Cabo Verde should be given the status of a biogeographic subprovince within the West African Transition province. We propose to redefine the Lusitanian biogeographical province, in which we include four ecoregions: the South European Atlantic Shelf, the Saharan Upwelling, the Azores, and a new ecoregion herein named Webbnesia, which comprises the archipelagos of Madeira, Selvagens and the Canary Islands.

Lack of Signal for the Impact of Conotoxin Gene Diversity on Speciation Rates in Cone Snails

Understanding why some groups of organisms are more diverse than others is a central goal in macroevolution. Evolvability, or the intrinsic capacity of lineages for evolutionary change, is thought to influence disparities in species diversity across taxa. Over macroevolutionary time scales, clades that exhibit high evolvability are expected to have higher speciation rates. Cone snails (family: Conidae, $>$900 spp.) provide a unique opportunity to test this prediction because their toxin genes can be used to characterize differences in evolvability between clades. Cone snails are carnivorous, use prey-specific venom (conotoxins) to capture prey, and the genes that encode venom are known and diversify through gene duplication. Theory predicts that higher gene diversity confers a greater potential to generate novel phenotypes for specialization and adaptation. Therefore, if conotoxin gene diversity gives rise to varying levels of evolvability, conotoxin gene diversity should be coupled with macroevolutionary speciation rates. We applied exon capture techniques to recover phylogenetic markers and conotoxin loci across 314 species, the largest venom discovery effort in a single study. We paired a reconstructed timetree using 12 fossil calibrations with species-specific estimates of conotoxin gene diversity and used trait-dependent diversification methods to test the impact of evolvability on diversification patterns. Surprisingly, we did not detect any signal for the relationship between conotoxin gene diversity and speciation rates, suggesting that venom evolution may not be the rate-limiting factor controlling diversification dynamics in Conidae. Comparative analyses showed some signal for the impact of diet and larval dispersal strategy on diversification patterns, though detection of a signal depended on the dataset and the method. If our results remain true with increased taxonomic sampling in future studies, they suggest that the rapid evolution of conid venom may cause other factors to become more critical to diversification, such as ecological opportunity or traits that promote isolation among lineages.

Characterization of the First Conotoxin from Conus ateralbus, a Vermivorous Cone Snail from the Cabo Verde Archipelago

Conus ateralbus is a cone snail endemic to the west side of the island of Sal, in the Cabo Verde Archipelago off West Africa. We describe the isolation and characterization of the first bioactive peptide from the venom of this species. This 30AA venom peptide is named conotoxin AtVIA (δ-conotoxin-like). An excitatory activity was manifested by the peptide on a majority of mouse lumbar dorsal root ganglion neurons. An analog of AtVIA with conservative changes on three amino acid residues at the C-terminal region was synthesized and this analog produced an identical effect on the mouse neurons. AtVIA has homology with δ-conotoxins from other worm-hunters, which include conserved sequence elements that are shared with δ-conotoxins from fish-hunting Conus. In contrast, there is no comparable sequence similarity with δ-conotoxins from the venoms of molluscivorous Conus species. A rationale for the potential presence of δ-conotoxins, that are potent in vertebrate systems in two different lineages of worm-hunting cone snails, is discussed.

Towards a 'Sea-Level Sensitive' dynamic model: impact of island ontogeny and glacio-eustasy on global patterns of marine island biogeography

A synthetic model is presented to enlarge the evolutionary framework of the General Dynamic Model (GDM) and the Glacial Sensitive Model (GSM) of oceanic island biogeography from the terrestrial to the marine realm. The proposed 'Sea-Level Sensitive' dynamic model (SLS) of marine island biogeography integrates historical and ecological biogeography with patterns of glacio-eustasy, merging concepts from areas as diverse as taxonomy, biogeography, marine biology, volcanology, sedimentology, stratigraphy, palaeontology, geochronology and geomorphology. Fundamental to the SLS model is the dynamic variation of the littoral area of volcanic oceanic islands (defined as the area between the intertidal and the 50-m isobath) in response to sea-level oscillations driven by glacial-interglacial cycles. The following questions are considered by means of this revision: (i) what was the impact of (global) glacio-eustatic sea-level oscillations, particularly those of the Pleistocene glacial-interglacial episodes, on the littoral marine fauna and flora of volcanic oceanic islands? (ii) What are the main factors that explain the present littoral marine biodiversity on volcanic oceanic islands? (iii) How can differences in historical and ecological biogeography be reconciled, from a marine point of view? These questions are addressed by compiling the bathymetry of 11 Atlantic archipelagos/islands to obtain quantitative data regarding changes in the littoral area based on Pleistocene sea-level oscillations, from 150 thousand years ago (ka) to the present. Within the framework of a model sensitive to changing sea levels, we discuss the principal factors affecting the geographical range of marine species; the relationships between modes of larval development, dispersal strategies and geographical range; the relationships between times of speciation, modes of larval development, ecological zonation and geographical range; the influence of sea-surface temperatures and latitude on littoral marine species diversity; the effect of eustatic sea-level changes and their impact on the littoral marine biota; island marine species-area relationships; and finally, the physical effects of island ontogeny and its associated submarine topography and marine substrate on littoral biota. Based on the SLS dynamic model, we offer a number of predictions for tropical, subtropical and temperate volcanic oceanic islands on how rates of immigration, colonization, in-situ speciation, local disappearance, and extinction interact and affect the marine biodiversity around islands during glacials and interglacials, thus allowing future testing of the theory.

Phylogenetic relationships of cone snails endemic to Cabo Verde based on mitochondrial genomes

BACKGROUND

Due to their great species and ecological diversity as well as their capacity to produce hundreds of different toxins, cone snails are of interest to evolutionary biologists, pharmacologists and amateur naturalists alike. Taxonomic identification of cone snails still relies mostly on the shape, color, and banding patterns of the shell. However, these phenotypic traits are prone to homoplasy. Therefore, the consistent use of genetic data for species delimitation and phylogenetic inference in this apparently hyperdiverse group is largely wanting. Here, we reconstruct the phylogeny of the cones endemic to Cabo Verde archipelago, a well-known radiation of the group, using mitochondrial (mt) genomes.

RESULTS

The reconstructed phylogeny grouped the analyzed species into two main clades, one including Kalloconus from West Africa sister to Trovaoconus from Cabo Verde and the other with a paraphyletic Lautoconus due to the sister group relationship of Africonus from Cabo Verde and Lautoconus ventricosus from Mediterranean Sea and neighboring Atlantic Ocean to the exclusion of Lautoconus endemic to Senegal (plus Lautoconus guanche from Mauritania, Morocco, and Canary Islands). Within Trovaoconus, up to three main lineages could be distinguished. The clade of Africonus included four main lineages (named I to IV), each further subdivided into two monophyletic groups. The reconstructed phylogeny allowed inferring the evolution of the radula in the studied lineages as well as biogeographic patterns. The number of cone species endemic to Cabo Verde was revised under the light of sequence divergence data and the inferred phylogenetic relationships.

CONCLUSIONS

The sequence divergence between continental members of the genus Kalloconus and island endemics ascribed to the genus Trovaoconus is low, prompting for synonymization of the latter. The genus Lautoconus is paraphyletic. Lautoconus ventricosus is the closest living sister group of genus Africonus. Diversification of Africonus was in allopatry due to the direct development nature of their larvae and mainly triggered by eustatic sea level changes during the Miocene-Pliocene. Our study confirms the diversity of cone endemic to Cabo Verde but significantly reduces the number of valid species. Applying a sequence divergence threshold, the number of valid species within the sampled Africonus is reduced to half.

Mitogenomic phylogeny of cone snails endemic to Senegal

Cone snails attain in Senegal one of their highest peaks of species diversity throughout the continental coast of Western Africa. A total of 15 endemic species have been described, all placed in the genus Lautoconus. While there is ample data regarding the morphology of the shell and the radular tooth of these species, virtually nothing is known regarding the genetic diversity and phylogenetic relationships of one of the most endangered groups of cones. In this work, we determined the complete or near-complete (only lacking the control region) mitochondrial (mt) genomes of 17 specimens representing 11 endemic species (Lautoconus belairensis, Lautoconus bruguieresi, Lautoconus cacao, Lautoconus cloveri, Lautoconus cf. echinophilus, Lautoconus guinaicus, Lautoconus hybridus, Lautoconus senegalensis, Lautoconus mercator, Lautoconus taslei, and Lautoconus unifasciatus). We also sequenced the complete mt genome of Lautoconus guanche from the Canary Islands, which has been related to the cones endemic to Senegal. All mt genomes share the same gene arrangement, which conforms to the consensus reported for Conidae, Neogastropoda and Caenogastropoda. Phylogenetic analyses using probabilistic methods recovered three major lineages, whose divergence coincided in time with sea level and ocean current changes as well as temperature fluctuations during the Messinian salinity crisis and the Plio-Pleistocene transition. Furthermore, the three lineages corresponded to distinct types of radular tooth (robust, small, and elongated), suggesting that dietary specialization could be an additional evolutionary driver in the diversification of the cones endemic to Senegal. The reconstructed phylogeny showed several cases of phenotypic convergence (cryptic species) and questions the validity of some species (ecotypes or phenotypic plasticity), both results having important taxonomic and conservation consequences.

Drivers of Cape Verde archipelagic endemism in keyhole limpets

Oceanic archipelagos are the ideal setting for investigating processes that shape species assemblages. Focusing on keyhole limpets, genera Fissurella and Diodora from Cape Verde Islands, we used an integrative approach combining molecular phylogenetics with ocean transport simulations to infer species distribution patterns and analyse connectivity. Dispersal simulations, using pelagic larval duration and ocean currents as proxies, showed a reduced level of connectivity despite short distances between some of the islands. It is suggested that dispersal and persistence driven by patterns of oceanic circulation favouring self-recruitment played a primary role in explaining contemporary species distributions. Mitochondrial and nuclear data revealed the existence of eight Cape Verde endemic lineages, seven within Fissurella, distributed across the archipelago, and one within Diodora restricted to Boavista. The estimated origins for endemic Fissurella and Diodora were 10.2 and 6.7 MY, respectively. Between 9.5 and 4.5 MY, an intense period of volcanism in Boavista might have affected Diodora, preventing its diversification. Having originated earlier, Fissurella might have had more opportunities to disperse to other islands and speciate before those events. Bayesian analyses showed increased diversification rates in Fissurella possibly promoted by low sea levels during Plio-Pleistocene, which further explain differences in species richness between both genera.

Cryptic diversity, geographical endemism and allopolyploidy in NE Pacific seaweeds

Background

Molecular markers are revealing a much more diverse and evolutionarily complex picture of marine biodiversity than previously anticipated. Cryptic and/or endemic marine species are continually being found throughout the world oceans, predominantly in inconspicuous tropical groups but also in larger, canopy-forming taxa from well studied temperate regions. Interspecific hybridization has also been found to be prevalent in many marine groups, for instance within dense congeneric assemblages, with introgressive gene-flow being the most common outcome. Here, using a congeneric phylogeographic approach, we investigated two monotypic and geographically complementary sister genera of north-east Pacific intertidal seaweeds (Hesperophycus and Pelvetiopsis), for which preliminary molecular tests revealed unexpected conflicts consistent with unrecognized cryptic diversity and hybridization.

Results

The three recovered mtDNA clades did not match a priori species delimitations. H. californicus was congruent, whereas widespread P. limitata encompassed two additional narrow-endemic species from California - P. arborescens (here genetically confirmed) and P. hybrida sp. nov. The congruence between the genotypic clusters and the mtDNA clades was absolute. Fixed heterozygosity was apparent in a high proportion of loci in P. limitata and P. hybrida, with genetic analyses showing that the latter was composed of both H. californicus and P. arborescens genomes. All four inferred species could be distinguished based on their general morphology.

Conclusions

This study confirmed additional diversity and reticulation within NE Pacific Hesperophycus/Pelvetiopsis, including the validity of the much endangered, modern climatic relict P. arborescens, and the identification of a new, stable allopolyploid species (P. hybrida) with clearly discernable ancestry (♀ H. californicus x ♂ P. arborescens), morphology, and geographical distribution. Allopolyploid speciation is otherwise completely unknown in brown seaweeds, and its unique occurrence within this genus (P. limitata possibly representing a second example) remains enigmatic. The taxonomic separation of Hesperophycus and Pelvetiopsis is not supported and the genera should be synonymized; we retain only the latter. The transitional coastline between Point Conception and Monterey Bay represented a diversity hotspot for the genus and the likely sites of extraordinary evolutionary events of allopolyploid speciation at sympatric range contact zones. This study pinpoints how much diversity (and evolutionary processes) potentially remains undiscovered even on a conspicuous seaweed genus from the well-studied Californian intertidal shores let alone in other, less studied marine groups and regions/depths.

Electronic supplementary material

The online version of this article (doi:10.1186/s12862-017-0878-2) contains supplementary material, which is available to authorized users.

Beyond Conus: Phylogenetic relationships of Conidae based on complete mitochondrial genomes

Understanding how the extraordinary taxonomic and ecological diversity of cone snails (Caenogastropoda: Conidae) evolved requires a statistically robust phylogenetic framework, which thus far is not available. While recent molecular phylogenies have been able to distinguish several deep lineages within the family Conidae, including the genera Profundiconus, Californiconus, Conasprella, and Conus (and within this one, several subgenera), phylogenetic relationships among these genera remain elusive. Moreover, the possibility that additional deep lineages may exist within the family is open. Here, we reconstructed with probabilistic methods a molecular phylogeny of Conidae using the newly sequenced complete or nearly complete mitochondrial (mt) genomes of the following nine species that represent all main Conidae lineages and potentially new ones: Profundiconus teramachii, Californiconus californicus, Conasprella wakayamaensis, Lilliconus sagei, Pseudolilliconus traillii, Conus (Kalloconus) venulatus, Conus (Lautoconus) ventricosus, Conus (Lautoconus) hybridus, and Conus (Eugeniconus) nobilis. To test the monophyly of the family, we also sequenced the nearly complete mt genomes of the following three species representing closely related conoidean families: Benthomangelia sp. (Mangeliidae), Tomopleura sp. (Borsoniidae), and Glyphostoma sp. (Clathurellidae). All newly sequenced conoidean mt genomes shared a relatively constant gene order with rearrangements limited to tRNA genes. The reconstructed phylogeny recovered with high statistical support the monophyly of Conidae and phylogenetic relationships within the family. The genus Profundiconus was placed as sister to the remaining genera. Within these, a clade including Californiconus and Lilliconus+Pseudolilliconus was the sister group of Conasprella to the exclusion of Conus. The phylogeny included a new lineage whose relative phylogenetic position was unknown (Lilliconus) and uncovered thus far hidden diversity within the family (Pseudolilliconus). Moreover, reconstructed phylogenetic relationships allowed inferring that the peculiar diet of Californiconus based on worms, mollusks, crustaceans and fish is derived, and reinforce the hypothesis that the ancestor of Conidae was a worm hunter. A chronogram was reconstructed under an uncorrelated relaxed molecular clock, which dated the origin of the family shortly after the Cretaceous-Tertiary boundary (about 59million years ago) and the divergence among main lineages during the Paleocene and the Eocene (56-30million years ago).

Species Selection Favors Dispersive Life Histories in Sea Slugs, but Higher Per-Offspring Investment Drives Shifts to Short-Lived Larvae

For 40 years, paleontological studies of marine gastropods have suggested that species selection favors lineages with short-lived (lecithotrophic) larvae, which are less dispersive than long-lived (planktotrophic) larvae. Although lecithotrophs appeared to speciate more often and accumulate over time in some groups, lecithotrophy also increased extinction rates, and tests for state-dependent diversification were never performed. Molecular phylogenies of diverse groups instead suggested lecithotrophs accumulate without diversifying due to frequent, unidirectional character change. Although lecithotrophy has repeatedly originated in most phyla, no adult trait has been correlated with shifts in larval type. Thus, both the evolutionary origins of lecithotrophy and its consequences for patterns of species richness remain poorly understood. Here, we test hypothesized links between development mode and evolutionary rates using likelihood-based methods and a phylogeny of 202 species of gastropod molluscs in Sacoglossa, a clade of herbivorous sea slugs. Evolutionary quantitative genetics modeling and stochastic character mapping supported 27 origins of lecithotrophy. Tests for correlated evolution revealed lecithotrophy evolved more often in lineages investing in extra-embryonic yolk, the first adult trait associated with shifts in development mode across a group. However, contrary to predictions from paleontological studies, species selection actually favored planktotrophy; most extant lecithotrophs originated through recent character change, and did not subsequently diversify. Increased offspring provisioning in planktotrophs thus favored shifts to short-lived larvae, which led to short-lived lineages over macroevolutionary time scales. These findings challenge long-standing assumptions about the effects of alternative life histories in the sea. Species selection can explain the long-term persistence of planktotrophy, the ancestral state in most clades, despite frequent transitions to lecithotrophy.

Molecular phylogeny and evolution of the cone snails (Gastropoda, Conoidea)

We present a large-scale molecular phylogeny that includes 320 of the 761 recognized valid species of the cone snails (Conus), one of the most diverse groups of marine molluscs, based on three mitochondrial genes (COI, 16S rDNA and 12S rDNA). This is the first phylogeny of the taxon to employ concatenated sequences of several genes, and it includes more than twice as many species as the last published molecular phylogeny of the entire group nearly a decade ago. Most of the numerous molecular phylogenies published during the last 15years are limited to rather small fractions of its species diversity. Bayesian and maximum likelihood analyses are mostly congruent and confirm the presence of three previously reported highly divergent lineages among cone snails, and one identified here using molecular data. About 85% of the species cluster in the single Large Major Clade; the others are divided between the Small Major Clade (∼12%), the Conus californicus lineage (one species), and a newly defined clade (∼3%). We also define several subclades within the Large and Small major clades, but most of their relationships remain poorly supported. To illustrate the usefulness of molecular phylogenies in addressing specific evolutionary questions, we analyse the evolution of the diet, the biogeography and the toxins of cone snails. All cone snails whose feeding biology is known inject venom into large prey animals and swallow them whole. Predation on polychaete worms is inferred as the ancestral state, and diet shifts to molluscs and fishes occurred rarely. The ancestor of cone snails probably originated from the Indo-Pacific; rather few colonisations of other biogeographic provinces have probably occurred. A new classification of the Conidae, based on the molecular phylogeny, is published in an accompanying paper.

Evolution at a different pace: distinctive phylogenetic patterns of cone snails from two ancient oceanic archipelagos

Ancient oceanic archipelagos of similar geological age are expected to accrue comparable numbers of endemic lineages with identical life history strategies, especially if the islands exhibit analogous habitats. We tested this hypothesis using marine snails of the genus Conus from the Atlantic archipelagos of Cape Verde and Canary Islands. Together with Azores and Madeira, these archipelagos comprise the Macaronesia biogeographic region and differ remarkably in the diversity of this group. More than 50 endemic Conus species have been described from Cape Verde, whereas prior to this study, only two nonendemic species, including a putative species complex, were thought to occur in the Canary Islands. We combined molecular phylogenetic data and geometric morphometrics with bathymetric and paleoclimatic reconstructions to understand the contrasting diversification patterns found in these regions. Our results suggest that species diversity is even lower than previously thought in the Canary Islands, with the putative species complex corresponding to a single species, Conus guanche. One explanation for the enormous disparity in Conus diversity is that the amount of available habitat may differ, or may have differed in the past due to eustatic (global) sea level changes. Historical bathymetric data, however, indicated that sea level fluctuations since the Miocene have had a similar impact on the available habitat area in both Cape Verde and Canary archipelagos and therefore do not explain this disparity. We suggest that recurrent gene flow between the Canary Islands and West Africa, habitat losses due to intense volcanic activity in combination with unsuccessful colonization of new Conus species from more diverse regions, were all determinant in shaping diversity patterns within the Canarian archipelago. Worldwide Conus species diversity follows the well-established pattern of latitudinal increase of species richness from the poles towards the tropics. However, the eastern Atlantic revealed a striking pattern with two main peaks of Conus species richness in the subtropical area and decreasing diversities toward the tropical western African coast. A Random Forests model using 12 oceanographic variables suggested that sea surface temperature is the main determinant of Conus diversity either at continental scales (eastern Atlantic coast) or in a broader context (worldwide). Other factors such as availability of suitable habitat and reduced salinity due to the influx of large rivers in the tropical area also play an important role in shaping Conus diversity patterns in the western coast of Africa.

Correlated evolution between mode of larval development and habitat in muricid gastropods

Larval modes of development affect evolutionary processes and influence the distribution of marine invertebrates in the ocean. The decrease in pelagic development toward higher latitudes is one of the patterns of distribution most frequently discussed in marine organisms (Thorson's rule), which has been related to increased larval mortality associated with long pelagic durations in colder waters. However, the type of substrate occupied by adults has been suggested to influence the generality of the latitudinal patterns in larval development. To help understand how the environment affects the evolution of larval types we evaluated the association between larval development and habitat using gastropods of the Muricidae family as a model group. To achieve this goal, we collected information on latitudinal distribution, sea water temperature, larval development and type of substrate occupied by adults. We constructed a molecular phylogeny for 45 species of muricids to estimate the ancestral character states and to assess the relationship between traits using comparative methods in a Bayesian framework. Our results showed high probability for a common ancestor of the muricids with nonpelagic (and nonfeeding) development, that lived in hard bottoms and cold temperatures. From this ancestor, a pelagic feeding larva evolved three times, and some species shifted to warmer temperatures or sand bottoms. The evolution of larval development was not independent of habitat; the most probable evolutionary route reconstructed in the analysis of correlated evolution showed that type of larval development may change in soft bottoms but in hard bottoms this change is highly unlikely. Lower sea water temperatures were associated with nonpelagic modes of development, supporting Thorson's rule. We show how environmental pressures can favor a particular mode of larval development or transitions between larval modes and discuss the reacquisition of feeding larva in muricids gastropods.

Conus: first comprehensive conservation red list assessment of a marine gastropod mollusc genus

Marine molluscs represent an estimated 23% of all extant marine taxa, but research into their conservation status has so far failed to reflect this importance, with minimal inclusion on the authoritative Red List of the International Union for the Conservation of Nature (IUCN). We assessed the status of all 632 valid species of the tropical marine gastropod mollusc, Conus (cone snails), using Red List standards and procedures to lay the groundwork for future decadal monitoring, one of the first fully comprehensive global assessments of a marine taxon. Three-quarters (75.6%) of species were not currently considered at risk of extinction owing to their wide distribution and perceived abundance. However, 6.5% were considered threatened with extinction with a further 4.1% near threatened. Data deficiency prevented 13.8% of species from being categorised although they also possess characteristics that signal concern. Where hotspots of endemism occur, most notably in the Eastern Atlantic, 42.9% of the 98 species from that biogeographical region were classified as threatened or near threatened with extinction. All 14 species included in the highest categories of Critically Endangered and Endangered are endemic to either Cape Verde or Senegal, with each of the three Critically Endangered species restricted to single islands in Cape Verde. Threats to all these species are driven by habitat loss and anthropogenic disturbance, in particular from urban pollution, tourism and coastal development. Our findings show that levels of extinction risk to which cone snails are exposed are of a similar magnitude to those seen in many fully assessed terrestrial taxa. The widely held view that marine species are less at risk is not upheld.

Conopeptides from Cape Verde Conus crotchii

Marine Cone snails of the genus Conus contain complex peptide toxins in their venom. Living in tropical habitats, they usually use the powerful venom for self-defense and prey capture. Here, we study Conus crotchii venom duct using a peptide mass-matching approach. The C. crotchii was collected on the Cape Verde archipelago in the Boa Vista Island. The venom was analyzed using matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF MS). About 488 molecular masses between 700 Da and 3000 Da were searched bymatching with known peptide sequences from UniProtKB protein sequence database. Through this method we were able to identify 12 conopeptides. For validation we considered the error between the experimental molecular mass (monoisotopic) and the calculated mass of less than 0.5 Da. All conopeptides detected belong to the A-, O1-, O2-, O3-, T- and D-superfamilies, which can block Ca²⁺ channels, inhibit K⁺ channels and act on nicotinic acetylcholine receptors (nAChRs). Only a few of the detected peptides have a 100% UniProtKB database similarity, suggesting that several of them could be newly discovered marine drugs.

Geometric morphometric character suites as phylogenetic data: extracting phylogenetic signal from gastropod shells

Despite being the objects of numerous macroevolutionary studies, many of the best represented constituents of the fossil record-including diverse examples such as foraminifera, brachiopods, and mollusks-have mineralized skeletons with limited discrete characteristics, making morphological phylogenies difficult to construct. In contrast to their paucity of phylogenetic characters, the mineralized structures (tests and shells) of these fossil groups frequently have distinctive shapes that have long proved useful for their classification. The recent introduction of methodologies for including continuous data directly in a phylogenetic analysis has increased the number of available characters, making it possible to produce phylogenies based, in whole or part, on continuous character data collected from such taxa. Geometric morphometric methods provide tools for accurately characterizing shape variation and can produce quantitative data that can therefore now be included in a phylogenetic matrix in a nonarbitrary manner. Here, the marine gastropod genus Conus is used to evaluate the ability of continuous characters-generated from a geometric morphometric analysis of shell shape-to contribute to a total evidence phylogenetic hypothesis constructed using molecular and morphological data. Furthermore, the ability of continuous characters derived from geometric morphometric analyses to place fossil taxa with limited discrete characters into a phylogeny with their extant relatives was tested by simulating the inclusion of fossil taxa. This was done by removing the molecular partition of individual extant species to produce a "cladistic pseudofossil" with only the geometric morphometric derived characters coded. The phylogenetic position of each cladistic pseudofossil taxon was then compared with its placement in the total evidence tree and a symmetric resampling tree to evaluate the degree to which morphometric characters alone can correctly place simulated fossil species. In 33-45% of the test cases (depending upon the approach used for measuring success), it was possible to place the pseudofossil taxon into the correct regions of the phylogeny using only the morphometric characters. This suggests that the incorporation of extinct Conus taxa into phylogenetic hypotheses will be possible, permitting a wide range of macroevolutionary questions to be addressed within this genus. This methodology also has potential to contribute to phylogenetic reconstructions for other major components of the fossil record that lack numerous discrete characters.

Macroevolution of venom apparatus innovations in auger snails (Gastropoda; Conoidea; Terebridae)

The Terebridae are a diverse family of tropical and subtropical marine gastropods that use a complex and modular venom apparatus to produce toxins that capture polychaete and enteropneust preys. The complexity of the terebrid venom apparatus suggests that venom apparatus development in the Terebridae could be linked to the diversification of the group and can be analyzed within a molecular phylogenetic scaffold to better understand terebrid evolution. Presented here is a molecular phylogeny of 89 terebrid species belonging to 12 of the 15 currently accepted genera, based on Bayesian inference and Maximum Likelihood analyses of amplicons of 3 mitochondrial (COI, 16S and 12S) and one nuclear (28S) genes. The evolution of the anatomy of the terebrid venom apparatus was assessed by mapping traits of six related characters: proboscis, venom gland, odontophore, accessory proboscis structure, radula, and salivary glands. A novel result concerning terebrid phylogeny was the discovery of a previously unrecognized lineage, which includes species of Euterebra and Duplicaria. The non-monophyly of most terebrid genera analyzed indicates that the current genus-level classification of the group is plagued with homoplasy and requires further taxonomic investigations. Foregut anatomy in the family Terebridae reveals an inordinate diversity of features that covers the range of variability within the entire superfamily Conoidea, and that hypodermic radulae have likely evolved independently on at least three occasions. These findings illustrate that terebrid venom apparatus evolution is not perfunctory, and involves independent and numerous changes of central features in the foregut anatomy. The multiple emergence of hypodermic marginal radular teeth in terebrids are presumably associated with variable functionalities, suggesting that terebrids have adapted to dietary changes that may have resulted from predator-prey relationships. The anatomical and phylogenetic results presented serve as a starting point to advance investigations about the role of predator-prey interactions in the diversification of the Terebridae and the impact on their peptide toxins, which are promising bioactive compounds for biomedical research and therapeutic drug development.

Phylogenetic relationships elucidate colonization patterns in the intertidal grazers Osilinus Philippi, 1847 and Phorcus Risso, 1826 (Gastropoda: Trochidae) in the northeastern Atlantic Ocean and Mediterranean Sea

Snails in the closely related trochid genera Phorcus Risso, 1826 and Osilinus Philippi, 1847 are ecologically important algal grazers in the intertidal zone of the northeastern Atlantic Ocean and Mediterranean Sea. Here we present the first complete molecular phylogeny for these genera, based on the nuclear 28S rRNA gene and the mitochondrial 16S rRNA and COI genes, and show that the current classification is erroneous. We recognize nine species in a single genus, Phorcus: estimated by BEAST analysis, this arose 30 (± 10) Ma; it consists of two subgenera, Phorcus and Osilinus, which we estimate diverged 14 (± 4.5) Ma. Osilinus kotschyi, from the Arabian and Red Seas, is not closely related and is tentatively referred to Priotrochus Fischer, 1879. Our phylogeny allows us to address biogeographical questions concerning the origins of the Mediterranean and Macaronesian species of this group. The former appear to have evolved from Atlantic ancestors that invaded the Mediterranean on several occasions after the Zanclean Flood, which ended the Messinian Salinity Crisis 5.3 Ma; whereas the latter arose from several colonizations of mainland Atlantic ancestors within the last 3 (± 1.5) Ma.

Replaying the tape: recurring biogeographical patterns in Cape Verde Conus after 12 million years

Isolated oceanic islands are excellent natural laboratories to test the relative role of historical contingency and determinism in evolutionary diversification. Endemics of the marine venomous snail Conus in the Cape Verde archipelago were originated from at least two independent colonizations of 'small' and 'large' shelled species separated by 12 million years. In this study, we have reconstructed phylogenetic relationships within large-shelled Conus (C. ateralbus, C. pseudonivifer, C. trochulus, and C. venulatus) based on mitochondrial cox1 and nad4 haplotype sequences. The reconstructed molecular phylogeny revealed three well-supported and relatively divergent clades (A, B, and C) that do not correspond to current species classification based on shell colour and banding patterns. Clade A grouped specimens assigned either to C. pseudonivifer or C. trochulus, clade B is composed of specimens assigned to C. venulatus, and clade C comprises specimens assigned either to C. venulatus or C. ateralbus. Geometric morphometric analyses found significant differences between the radular teeth shape of C. pseudonivifer/C. trochulus and C. venulatus/C. ateralbus. In clades A and B, northwestern Boavista and Maio specimens cluster together to the exclusion of eastern Boavista samples. In Sal, populations form a monophyletic island assemblage (clade C). The large-shelled Conus have remarkably replicated biogeographical patterns of diversification of small-shelled Conus. Similar selective forces (i.e. nonplanktonic lecithotrophy with limited larval dispersal and allopatric diversification) together with repeated instances of low sea level stands during glacial maxima that allowed connection between islands, have overcome the effect of historical contingency, and explain the observed recurring biogeographical patterns.

Patterns of colonization, evolution and gene flow in species of the genus Patella in the Macaronesian Islands

The study of phylogeographical patterns may contribute to a better understanding of factors affecting the dispersal of organisms in ecological and historical times. For intertidal organisms, islands are particularly suitable models allowing the test of predictions related to the efficacy of pelagic larvae dispersal. Here, we study the phylogeographical patterns and gene flow within three groups of species of the genus Patella present in the Macaronesian Islands that have been previously shown to be monophyletic. The genetic variability of around 600 bp of the mitochondrial gene cytochrome c oxidase subunit I was studied by single strand conformation polymorphism and/or sequencing for seven species of limpets. A total of 420 samples were analysed from the Macaronesian archipelagos, North Africa, and Atlantic and Mediterranean shores of the Iberian Peninsula. No clear geographical pattern or temporal congruence was found between the three groups of species, pointing to independent histories and colonization events. However, for the three groups, the split between the Macaronesian and the mainland forms most probably occurred before 3.9 million years ago, predating the establishment of the current circulation patterns. The presence of pelagic larvae in these species is shown to be insufficient to ensure gene flow between continental and Macaronesian populations and between the Macaronesian archipelagos. In the endangered Azorean populations of Patella candei, there is restricted gene flow to Flores and Graciosa.

Multiple origins of the Juan Fernández kelpfish fauna and evidence for frequent and unidirectional dispersal of cirrhitoid fishes across the South Pacific

Phylogenetic relationships were reconstructed among chironemid fishes based on morphological and molecular (lrRNA, NADH4, S7 ribosomal protein) characters. Two sympatric species from Juan Fernández in the southeast Pacific are not sister taxa, but rather exhibit independent relationships to Australian/New Zealand chironemids. The most plausible explanation for these relationships and contemporary distributions is an Australian/New Zealand origin of the family, followed by two trans-Pacific dispersal and colonization events, facilitated by larval entrapment within the West Wind Drift. This study demonstrates that the diversity of taxa on an island can reflect multiple colonizations, rather than in situ diversification, even in the case of very small, isolated, and geologically recent islands. When taken in conjunction with studies of related taxa, our results indicate that transoceanic dispersal of temperate cirrhitoid fishes in the South Pacific has been frequent and unidirectional. Molecular estimates of divergence time between southeast Pacific chironemids and their western relatives predate the emergence of Juan Fernández, consistent with hypotheses that much of the marine nearshore faunas of young southeast Pacific islands may be the product of successive transfer from older, now submerged islands.