Tropical range extension for the temperate, endemic South-Eastern Australian Nudibranch Goniobranchus splendidus (Angas, 1864)

In contrast to many tropical animals expanding southwards on the Australian coast concomitant with climate change, here we report a temperate endemic newly found in the tropics. Chromodorid nudibranchs are bright, colourful animals that rarely go unnoticed by divers and underwater photographers. The discovery of a new population, with divergent colouration is therefore significant. DNA sequencing confirms that despite departures from the known phenotypic variation, the specimen represents northern Goniobranchus splendidus and not an unknown close relative. Goniobranchus tinctorius represents the sister taxa to G. splendidus. With regard to secondary defences, the oxygenated terpenes found previously in this specimen are partially unique but also overlap with other G. splendidus from southern Queensland (QLD) and New South Wales (NSW). The tropical specimen from Mackay contains extracapsular yolk like other G. splendidus. This previously unknown tropical population may contribute selectively advantageous genes to cold-water species threatened by climate change. Competitive exclusion may explain why G. splendidus does not strongly overlap with its widespread sister taxon

Mimicry and mitonuclear discordance in nudibranchs : new insights from exon capture phylogenomics

Open access via the Wiley Jisc Agreement Funding Information Gorgon Barrow Island Net Conservation Benefits Fund The University of Western Australia Malacological Society of Australasia ACKNOWLEDGEMENTS We are grateful to our collaborators who have contributed specimens to this work, including David Mullins, Gary Cobb, Greg Rouse, Karen Cheney, Kate Dawson, Lisa Kirkendale, Terry Farr, and Terry Gosliner. We also thank Elizabeth Kools for coordinating K.K.S.L's tissue sampling at the California Academy of Sciences and for sending specimens for this work. We sincerely thank Alison Devault and Jakob Enk from Arbor Biosciences for logistical support and advice, and Greg Rouse, Joel Huey, and Josefin Stiller for feedback on data analysis. Funding for this project comes from the Gorgon Project's Barrow Island Net Conservation Benefits Fund, The University of Western Australia, and the Malacological Society of Australasia. K.K.S.L. was supported by a University Postgraduate Award for International Students (UPAIS) and an RTP International Fees Offset scholarship (RTPFI) administered by the University of Western Australia, as well as a postgraduate doctoral scholarship from the Natural Sciences and Engineering Research Council of Canada (NSERC). Here we provide permit details for newly collected specimens that do not derive from Layton et al. (2018). Specimens from Western Australia were collected under permits from the Department of Parks and Wildlife, including a regulation 17 licence to collect fauna for scientific purposes (SF010218, SF010710) and a regulation 4 exemption to collect marine invertebrates within Ningaloo Marine Park (CE005306). Specimens from Queensland were collected under permits from the Department of Agriculture, Fisheries and Forestry (Permit #: 183990). Specimens from Victoria were collected under permits from the Department of Environment, Land, Water and Planning (Permit #: 10007853). The specimen from California was collected under a permit from California Department of Fish and Wildlife (Permit #: 4564).Peer reviewedPublisher PD

A newly discovered radiation of endoparasitic gastropods and their coevolution with asteroid hosts in Antarctica

Funding Funding for this research comes from the Antarctic Circumnavigation Expedition, The University of Western Australia, and the National Science Foundation (USA) ANT-1043749. KKSL was supported by a University Postgraduate Award for International Students (UPAIS) and an RTP International Fees Offset scholarship (RTPFI) administered by The University of Western Australia, as well as a postgraduate doctoral scholarship from the Natural Sciences and Engineering Research Council of Canada (NSERC). These funding bodies did not have a role in the design of the study, the collection, analysis, and interpretation of data, or in writing the manuscript. Availability of data and materials The datasets used and/or analysed during the current study are available from the corresponding author on reasonable request and GenBank accessions appear in the manuscript.Peer reviewedPublisher PD

Ringiculid bubble snails recovered as the sister group to sea slugs (Nudipleura)

Euthyneuran gastropods represent one of the most diverse lineages in Mollusca (with over 30,000 species), play significant ecological roles in aquatic and terrestrial environments and affect many aspects of human life. However, our understanding of their evolutionary relationships remains incomplete due to missing data for key phylogenetic lineages. The present study integrates such a neglected, ancient snail family Ringiculidae into a molecular systematics of Euthyneura for the first time, and is supplemented by the first microanatomical data. Surprisingly, both molecular and morphological features present compelling evidence for the common ancestry of ringiculid snails with the highly dissimilar Nudipleura-the most species-rich and well-known taxon of sea slugs (nudibranchs and pleurobranchoids). A new taxon name Ringipleura is proposed here for these long-lost sisters, as one of three major euthyneuran clades with late Palaeozoic origins, along with Acteonacea (Acteonoidea + Rissoelloidea) and Tectipleura (Euopisthobranchia + Panpulmonata). The early Euthyneura are suggested to be at least temporary burrowers with a characteristic 'bubble' shell, hypertrophied foot and headshield as exemplified by many extant subtaxa with an infaunal mode of life, while the expansion of the mantle might have triggered the explosive Mesozoic radiation of the clade into diverse ecological niches

Detecting glacial refugia in the Southern Ocean

Throughout the Quaternary, the continental‐based Antarctic ice sheets expanded and contracted repeatedly. Evidence suggests that during glacial maxima, grounded ice eliminated most benthic (bottom‐dwelling) fauna across the Antarctic continental shelf. However, paleontological and molecular evidence indicates most extant Antarctica benthic taxa have persisted in situ throughout the Quaternary. Where and how the Antarctic benthic fauna survived throughout repeated glacial maxima remain mostly hypothesised. If understood, this would provide valuable insights into the ecology and evolution of Southern Ocean biota over geological timescales. Here we synthesised and appraised recent studies and presented an approach to demonstrate how genetic data can be effective in identifying where and how Antarctic benthic fauna survived glacial periods. We first examined the geological and ecological evidence for how glacial periods influenced past species demography in order to provide testable frameworks for future studies. We outlined past ice‐free areas from Antarctic ice sheet reconstructions that could serve as glacial refugia and discussed how benthic fauna with pelagic or non‐pelagic dispersal strategies moved into and out of glacial refugia. We also reviewed current molecular studies and collated proposed locations of Southern Ocean glacial refugia on the continental shelf around Antarctica, in the deep sea, and around sub‐Antarctic islands. Interestingly, the proposed glacial refugia based on molecular data generally do not correspond to the ice‐free areas identified by Antarctic ice sheet reconstructions. The potential biases in sampling and in the choice of molecular markers in current literature are discussed, along with the future directions for employing testable frameworks and genomic methods in Southern Ocean molecular studies. Continued data syntheses will elucidate greater understanding of where and how Southern Ocean benthic fauna persisted throughout glacial periods and provide insights into their resilience against climate changes in the future

Host specificity versus plasticity: testing the morphology-based taxonomy of the endoparasitic copepod family Splanchnotrophidae with COI barcoding

The Splanchnotrophidae is a family of highly modified endoparasitic copepods known to infest nudibranch or sacoglossan sea slug hosts. Most splanchnotrophid species appear to be specific to a single host, but some were reported from up to nine different host species. However, splanchnotrophid taxonomy thus far is based on external morphology, and taxonomic descriptions are, mostly, old and lack detail. They are usually based on few specimens, with intraspecific variability rarely reported. The present study used molecular data for the first time to test (1) the current taxonomic hypotheses, (2) the apparently strict host specificity of the genus Ismaila and (3) the low host specificity of the genus Splanchnotrophus with regard to the potential presence of cryptic species. Phylogenetic analyses herein used sequences of the barcoding region of the cytochrome oxidase I (COI) gene from 40 specimens representing 13 species of five genera. Species delimitation approaches include distance and barcoding gap analyses, haplotype networks and diagnostic nucleotides. Molecular results are largely compatible with the commonly accepted, morphology-based taxonomy of the Splanchnotrophidae. Strict host specificity could be confirmed for two Ismaila species. COI analyses also supported the idea that Splanchnotrophus angulatus is host-promiscuous. In Ismaila, morphology seems more suitable than barcoding to display speciation events via host switches in a recent Chilean radiation. In Splanchnotrophus, some genetic structure suggests ongoing diversification, which should be investigated further given the inadequate morphology-based taxonomy. The present study thus supports the presence of two different life history strategies in splanchnotrophids, which should be explored integratively

Emerging biological archives can reveal ecological and climatic change in Antarctica

Anthropogenic climate change is causing observable changes in Antarctica and the Southern Ocean including increased air and ocean temperatures, glacial melt leading to sea-level rise and a reduction in salinity, and changes to freshwater water availability on land. These changes impact local Antarctic ecosystems and the Earth's climate system. The Antarctic has experienced significant past environmental change, including cycles of glaciation over the Quaternary Period (the past similar to 2.6 million years), Understanding Antarctica's paleoecosystems, and the corresponding paleoenvironments and climates that have shaped them, provides insight into present day ecosystem change, and importantly, helps constrain model projections of future change. Biological archives such as extant moss beds and peat profiles, biological proxies in lake and marine sediments, vertebrate animal colonies, and extant terrestrial and benthic marine invertebrates, complement other Antarctic paleoclimate archives by recording the nature and rate of past ecological change, the paleoenvironmental drivers of that change, and constrain current ecosystem and climate models. These archives provide invaluable information about terrestrial ice-free areas, a key location for Antarctic biodiversity, and the continental margin which is important for understanding ice sheet dynamics. Recent significant advances in analytical techniques (e.g., genomics, biogeochemical analyses) have led to new applications and greater power in elucidating the environmental records contained within biological archives. Paleoecological and paleoclimate discoveries derived from biological archives, and integration with existing data from other paleoclimate data sources, will significantly expand our understanding of past, present, and future ecological change, alongside climate change, in a unique, globally significant region

Evolutionary innovations in Antarctic brittle stars linked to glacial refugia

The drivers behind evolutionary innovations such as contrasting life histories and morphological change are central questions of evolutionary biology. However, the environmental and ecological contexts linked to evolutionary innovations are generally unclear. During the Pleistocene glacial cycles, grounded ice sheets expanded across the Southern Ocean continental shelf. Limited ice-free areas remained, and fauna were isolated from other refugial populations. Survival in Southern Ocean refugia could present opportunities for ecological adaptation and evolutionary innovation. Here, we reconstructed the phylogeographic patterns of circum-Antarctic brittle stars Ophionotus victoriae and O. hexactis with contrasting life histories (broadcasting vs brooding) and morphology (5 vs 6 arms). We examined the evolutionary relationship between the two species using cytochrome c oxidase subunit I (COI) data. COI data suggested that O. victoriae is a single species (rather than a species complex) and is closely related to O. hexactis (a separate species). Since their recent divergence in the mid-Pleistocene, O. victoriae and O. hexactis likely persisted differently throughout glacial maxima, in deep-sea and Antarctic island refugia, respectively. Genetic connectivity, within and between the Antarctic continental shelf and islands, was also observed and could be linked to the Antarctic Circumpolar Current and local oceanographic regimes. Signatures of a probable seascape corridor linking connectivity between the Scotia Sea and Prydz Bay are also highlighted. We suggest that survival in Antarctic island refugia was associated with increase in arm number and a switch from broadcast spawning to brooding in O. hexactis, and propose that it could be linked to environmental changes (such as salinity) associated with intensified interglacial-glacial cycles

Fixed, Free, and Fixed: The Fickle Phylogeny of Extant Crinoidea (Echinodermata) and Their Permian-Triassic Origin

Although the status of Crinoidea (sea lilies and featherstars) as sister group to all other living echinoderms is well-established, relationships among crinoids, particularly extant forms, are debated. All living species are currently placed in Articulata, which is generally accepted as the only crinoid group to survive the Permian–Triassic extinction event. Recent classifications have recognized five major extant taxa: Isocrinida, Hyocrinida, Bourgueticrinina, Comatulidina and Cyrtocrinida, plus several smaller groups with uncertain taxonomic status, e.g., Guillecrinus, Proisocrinus and Caledonicrinus. Here we infer the phylogeny of extant Crinoidea using three mitochondrial genes and two nuclear genes from 59 crinoid terminals that span the majority of extant crinoid diversity. Although there is poor support for some of the more basal nodes, and some tree topologies varied with the data used and mode of analysis, we obtain several robust results. Cyrtocrinida, Hyocrinida, Isocrinida are all recovered as clades, but two stalked crinoid groups, Bourgueticrinina and Guillecrinina, nest among the featherstars, lending support to an argument that they are paedomorphic forms. Hence, they are reduced to families within Comatulida. Proisocrinus is clearly shown to be part of Isocrinida, and Caledonicrinus may not be a bourgueticrinid. Among comatulids, tree topologies show little congruence with current taxonomy, indicating that much systematic revision is required. Relaxed molecular clock analyses with eight fossil calibration points recover Articulata with a median date to the most recent common ancestor at 231–252 mya in the Middle to Upper Triassic. These analyses tend to support the hypothesis that the group is a radiation from a small clade that passed through the Permian–Triassic extinction event rather than several lineages that survived. Our tree topologies show various scenarios for the evolution of stalks and cirri in Articulata, so it is clear that further data and taxon sampling are needed to recover a more robust phylogeny of the group

Phylogeography of recent <i>Plesiastrea</i> (Scleractinia::Plesiastreidae) based on an integrated taxonomic approach

Scleractinian corals are a diverse group of ecologically important yet highly threatened marine invertebrates, which can be challenging to identify to the species level. An influx of molecular studies has transformed scleractinian systematics, highlighting that cryptic species may be more common than previously understood. In this study, we test the hypothesis that Plesiastrea versipora (Lamarck, 1816), a species currently considered to occur throughout the Indo-Pacific in tropical, sub-tropical and temperate waters, is a single species. Molecular and morphological analyses were conducted on 80 samples collected from 31 sites spanning the majority of the species putative range and twelve mitogenomes were assembled to identify informative regions for phylogenetic reconstruction. Congruent genetic data across three gene regions supports the existence of two monophyletic clades aligning with distinct tropical and temperate provenances. Multivariate macromorphological analyses based on 13 corallite characters provided additional support for the phylogeographic split, with the number of septa and corallite density varying across this biogeographic divide. Furthermore, micromorphological and microstructural analyses identified that the temperate representatives typically develop sub-cerioid corallites with sparse or absent coenosteal features and smooth septal faces. In contrast, tropical representatives typically develop plocoid corallites separated by a porous dissepimental coenosteum and have granulated septal faces. These data suggest that at least two species exist within the genus PlesiastreaMilne Edwards & Haime, 1848. Based on examination of type material, we retain the name Plesiastrea versipora (Lamarck, 1816) for the temperate representatives of the genus and resurrect the name Plesiastrea peroniMilne Edwards & Haime, 1857 for the tropical members. This study highlights how broadly distributed hard coral taxa still need careful re-examination through an integrated systematics approach to better understand their phylogeographic patterns. Furthermore, it demonstrates the utility of integrating micro-, macro-morphological and genetic datasets, and the importance of type specimens when dealing with taxonomic revisions of scleractinian taxa