Molecular phylogenetics reveals the evolutionary history of marine fishes (Actinopterygii) endemic to the subtropical islands of the Southwest Pacific.

Remote oceanic islands of the Pacific host elevated levels of actinopterygian (ray-finned fishes) endemism. Characterizing the evolutionary histories of these endemics has provided insight into the generation and maintenance of marine biodiversity in many regions. The subtropical islands of Lord Howe, Norfolk, and Rangitahua (Kermadec) in the Southwest Pacific are yet to be comprehensively studied. Here, we characterize the spatio-temporal diversification of marine fishes endemic to these Southwest Pacific islands by combining molecular phylogenies and the geographic distribution of species. We built Bayesian ultrametric trees based on open-access and newly generated sequences for five mitochondrial and ten nuclear loci, and using fossil data for time calibration. We present the most comprehensive phylogenies to date for marine ray-finned fish genera, comprising 34 species endemic to the islands, including the first phylogenetic placements for 11 endemics. Overall, our topologies confirm the species status of all endemics, including three undescribed taxa. Our phylogenies highlight the predominant affinity of these endemics with the Australian fish fauna (53%), followed by the East Pacific (15%), and individual cases where the closest sister taxon of our endemic is found in the Northwest Pacific and wider Indo-Pacific. Nonetheless, for a quarter of our focal endemics, their geographic affinity remains unresolved due to sampling gaps within their genera. Our divergence time estimates reveal that the majority of endemic lineages (67.6%) diverged after the emergence of Lord Howe (6.92 Ma), the oldest subtropical island in the Southwest Pacific, suggesting that these islands have promoted diversification. However, divergence ages of some endemics pre-date the emergence of the islands, suggesting they may have originated outside of these islands, or, in some cases, ages may be overestimated due to unsampled taxa. To fully understand the role of the Southwest Pacific subtropical islands as a 'cradle' for diversification, our study advocates for further regional surveys focused on tissue collection for DNA analysis.

Phylogenomic Species Delimitation Dramatically Reduces Species Diversity in an Antarctic Adaptive Radiation.

Application of genetic data to species delimitation often builds confidence in delimitations previously hypothesized using morphological, ecological, and geographic data and frequently yields recognition of previously undescribed cryptic diversity. However, a recent critique of genomic data-based species delimitation approaches is that they have the potential to conflate population structure with species diversity, resulting in taxonomic oversplitting. The need for an integrative approach to species delimitation, in which molecular, morphological, ecological, and geographic lines of evidence are evaluated together, is becoming increasingly apparent. Here, we integrate phylogenetic, population genetic, and coalescent analyses of genome-wide sequence data with investigation of variation in multiple morphological traits to delimit species within the Antarctic barbeled plunderfishes (Artedidraconidae: Pogonophryne). Pogonophryne currently comprises 29 valid species, most of which are distinguished solely by variation in the ornamentation of the mental barbel that projects from the lower jaw, a structure previously shown to vary widely within a single species. However, our genomic and phenotypic analyses result in a dramatic reduction in the number of distinct species recognized within the clade, providing evidence to support the recognition of no more than six species. We propose to synonymize 24 of the currently recognized species with five species of Pogonophryne. We find genomic and phenotypic evidence for a new species of Pogonophryne from specimens collected in the Ross Sea. Our findings represent a rare example in which the application of molecular data provides evidence of taxonomic oversplitting on the basis of morphology, clearly demonstrating the utility of an integrative species delimitation framework.[ddRADseq; multispecies coalescent; Notothenioidei; SNPs; Southern Ocean.].

Phylogenetic analysis of Antarctic notothenioids illuminates the utility of RADseq for resolving Cenozoic adaptive radiations.

Notothenioids are a clade of ∼120 species of marine fishes distributed in extreme southern hemisphere temperate near-shore habitats and in the Southern Ocean surrounding Antarctica. Over the past 25 years, molecular and morphological approaches have redefined hypotheses of relationships among notothenioid lineages as well as their relationships among major lineages of percomorph teleosts. These phylogenies provide a basis for investigation of mechanisms of evolutionary diversification within the clade and have enhanced our understanding of the notothenioid adaptive radiation. Despite extensive efforts, there remain several questions concerning the phylogeny of notothenioids. In this study, we deploy DNA sequences of ∼100,000 loci obtained using RADseq to investigate the phylogenetic relationships of notothenioids and to assess the utility of RADseq loci for lineages that exhibit divergence times ranging from the Paleogene to the Quaternary. The notothenioid phylogenies inferred from the RADseq loci provide unparalleled resolution and node support for several long-standing problems including, (1) relationships among species of Trematomus, (2) resolution of Indonotothenia cyanobrancha as the sister lineage of Trematomus, (3) the deep paraphyly of Nototheniidae, (4) the paraphyly of Lepidonotothen s.l., (5) paraphyly of Artedidraco, and 6) the monophyly of the Bathydraconidae. Assessment of site rates demonstrates that RADseq loci are similar to mtDNA protein coding genes and exhibit peak phylogenetic informativeness at the time interval during which the major Antarctic notothenioid lineages originated and diversified. In addition to providing a well-resolved phylogenetic hypothesis for notothenioids, our analyses quantify the predicted utility of RADseq loci for Cenozoic phylogenetic inferences.

Redescription of the Indo-Pacific scorpionfish Scorpaenodes guamensis (Quoy & Gaimard 1824) (Scorpaenidae), a senior synonym of seven nominal species.

The Indo-Pacific scorpionfish, Scorpaenodes guamensis (Quoy & Gaimard 1824), is redescribed on the basis of 137 specimens, including types, from a wide geographic range in the Indo-Pacific. Seven nominal species, Scorpaena rubropunctata Cuvier in Cuvier & Valenciennes 1829, Sebastes minutus Cuvier in Cuvier & Valenciennes 1829, Scorpaena chilioprista Rüppell 1838, Scorpaena polylepis Bleeker 1851, Centropogon echinatus Macleay 1881, Scorpaena erinacea Garman 1903, and Scorpaenopsis quiescens Seale 1906, are regarded here as junior synonyms of S. guamensis. The type status of these nominal species is discussed, and lectotypes of Scorpaena guamensis, Scorpaena rubropunctata, Sebastes minutus, and Scorpaena polylepis are herein designated. Validity of Scorpaenopsis scaber (Ramsay & Ogilby 1886) is also discussed.

Three new species of the Indo-Pacific fish genus Hime (Aulopidae, Aulopiformes), all resembling the type species H. japonica (Günther 1877).

Descriptions of three new species of the aulopid genus Hime from the central and western Pacific and presumably the easternmost Indian Ocean are presented. Hime surrubea sp. nov., confined to the Hawaiian Island region, has been misidentified in species accounts and faunal lists as H. japonica and although resembling it is separable from that species by its shorter caudal peduncle, slightly larger head, larger eye, especially relative to head size, and slightly smaller pectoral and pelvic fins. Hime capitonis sp. nov. is known conclusively only from seamounts off the southern tip of New Caledonia and Vanuatu, and is distinguishable by its distinctively large head (32.3-35.6% SL) and eyes (orbital diameter 10.8-13.0% SL) and relatively few scales between the anus and anal fin origin (7-9). The Indonesian H. caudizoma sp. nov. is so far known from only 8 specimens, acquired in markets in southeastern Lombok and presumably caught nearby in what would be regarded the eastern reaches of the Indian Ocean. The species is recognisable by its dorsal fin of rather uniform moderate height with nearly straight distal margin and 17 rather than 16 rays, none of which is filamentous in either sex, the second penultimate ray rather than anterior rays the longest in males. Like the other two described here, H. caudizoma has among the largest head and eyes of the family. Observations on the dorsal fin form and other features of H. microps Parin & Kotlyar, 1989 are provided based on a large male specimen collected at Rapa Iti, Austral Islands and a re-evaluation of the original description.

Parapercis nigrodorsalis (Perciformes: Pinguipedidae), a new species of sandperch from northern New Zealand and the Norfolk Ridge, Tasman Sea and remarks on P. binivirgata (Waite, 1904).

A new species of pinguipedid fish, Parapercis nigrodorsalis, is described from 17 specimens collected off the North Island of New Zealand and Wanganella Bank, Norfolk Ridge, Tasman Sea, in depths of 56-280 m. The species has also been photographed underwater off the Poor Knights Islands Reserve and Burgess Island, Mokohinau Group, in New Zealand. It is most similar to Parapercis binivirgata (Waite, 1904) in morphology, coloration and meristic values, but is unique among the genus in having a combination of dorsal-fin rays V, 23, anal-fin rays I, 19, lateral-line scales 57-63, vomer with 1-2 irregular rows of robust conical teeth, palatines with 1-2 rows of small teeth, angle of subopercle smooth, 10 abdominal and 22 caudal vertebrae, and coloration, including seven broad reddish-brown bands on the upper body between the spinous dorsal-fin and the caudal peduncle, most bands bifurcated into close-set double bars with black smudge-like blotches below, and membrane of the spinous dorsal fin black. Comparison of the mitochondrial cytochrome c oxidase subunit 1 (CO 1) genetic marker utilised in DNA barcoding produced a genetic divergence of 5.38% and 7.63% between the new species and its two closest sampled congeners. The holotype of P. binivirgata is identified from two specimens previously regarded as syntypes, some revisions are made to meristic data in the original description of the latter, and a detailed description of the revised geographic range of P. binivirgata is provided.  

Diversity and composition of demersal fishes along a depth gradient assessed by baited remote underwater stereo-video.

BACKGROUND: Continental slopes are among the steepest environmental gradients on earth. However, they still lack finer quantification and characterisation of their faunal diversity patterns for many parts of the world. METHODOLOGY/PRINCIPAL FINDINGS: Changes in fish community structure and diversity along a depth gradient from 50 to 1200 m were studied from replicated stereo baited remote underwater video deployments within each of seven depth zones at three locations in north-eastern New Zealand. Strong, but gradual turnover in the identities of species and community structure was observed with increasing depth. Species richness peaked in shallow depths, followed by a decrease beyond 100 m to a stable average value from 700 to 1200 m. Evenness increased to 700 m depth, followed by a decrease to 1200 m. Average taxonomic distinctness △(+) response was unimodal with a peak at 300 m. The variation in taxonomic distinctness Λ(+) first decreased sharply from 50 to 300 m, then increased beyond 500 m depth, indicating that species from deep samples belonged to more distant taxonomic groups than those from shallow samples. Fishes with northern distributions progressively decreased in their proportional representation with depth whereas those with widespread distributions increased. CONCLUSIONS/SIGNIFICANCE: This study provides the first characterization of diversity patterns for bait-attracted fish species on continental slopes in New Zealand and is an imperative primary step towards development of explanatory and predictive ecological models, as well as being fundamental for the implementation of efficient management and conservation strategies for fishery resources.

Hagfish predatory behaviour and slime defence mechanism.

Hagfishes (Myxinidae), a family of jawless marine pre-vertebrates, hold a unique evolutionary position, sharing a joint ancestor with the entire vertebrate lineage. They are thought to fulfil primarily the ecological niche of scavengers in the deep ocean. However, we present new footage from baited video cameras that captured images of hagfishes actively preying on other fish. Video images also revealed that hagfishes are able to choke their would-be predators with gill-clogging slime. This is the first time that predatory behaviour has been witnessed in this family, and also demonstrates the instantaneous effectiveness of hagfish slime to deter fish predators. These observations suggest that the functional adaptations and ecological role of hagfishes, past and present, might be far more diverse than previously assumed. We propose that the enduring success of this oldest extant family of fishes over 300 million years could largely be due to their unique combination of functional traits.