Tightening the requirements for species diagnoses would help integrate DNA-based descriptions in taxonomic practice.

Modern advances in DNA sequencing hold the promise of facilitating descriptions of new organisms at ever finer precision but have come with challenges as the major Codes of bionomenclature contain poorly defined requirements for species and subspecies diagnoses (henceforth, species diagnoses), which is particularly problematic for DNA-based taxonomy. We, the commissioners of the International Commission on Zoological Nomenclature, advocate a tightening of the definition of "species diagnosis" in future editions of Codes of bionomenclature, for example, through the introduction of requirements for specific information on the character states of differentiating traits in comparison with similar species. Such new provisions would enhance taxonomic standards and ensure that all diagnoses, including DNA-based ones, contain adequate taxonomic context. Our recommendations are intended to spur discussion among biologists, as broad community consensus is critical ahead of the implementation of new editions of the International Code of Zoological Nomenclature and other Codes of bionomenclature.

Molecular phylogeny of deep-sea blind lobsters of the family Polychelidae (Decapoda: Polychelida), with implications for the origin and evolution of these "living fossils".

A comprehensive molecular analysis of the deep-sea blind lobsters of the family Polychelidae, often referred to as "living fossils", is conducted based on all six modern genera and 27 of the 38 extant species. Using six genetic markers from both mitochondrial and nuclear genomes, the molecular phylogenetic results differ considerably from previous morphological analyses and reveal the genera Polycheles and Pentacheles to be para- or polyphyletic. As the splitting of Polycheles has strong support from both molecular and morphological data, two new genera, Dianecheles and Neopolycheles, are erected for those species excluded from the clade containing the type species of Polycheles. The pattern of polyphyly of Pentacheles, however, is not robustly resolved, so it is retained as a single genus. Fossil evidence suggests that fossil polychelids inhabited deep-sea environments as early as the Early to Middle Jurassic, demonstrating the enduring adaptation of extant polychelid species to the deep-sea. Time-calibrated phylogeny suggested that modern polychelids probably had an Atlantic origin during the Jurassic period. Since their emergence, this ancient lobster group has continued to diversify, particularly in the West Pacific, and has colonized the abyssal zone, with the deepest genus, Willemoesia, representing the more 'derived' members among extant polychelids. Differences in eye reduction among extant polychelid genera highlight the necessity for ongoing investigations to ascertain the relative degree of functionality of their eyes, if they indeed retain any function.

Convergent adaptation of true crabs (Decapoda: Brachyura) to a gradient of terrestrial environments.

For much of terrestrial biodiversity, the evolutionary pathways of adaptation from marine ancestors are poorly understood, and have usually been viewed as a binary trait. True crabs, the decapod crustacean infraorder Brachyura, comprise over 7,600 species representing a striking diversity of morphology and ecology, including repeated adaptation to non-marine habitats. Here, we reconstruct the evolutionary history of Brachyura using new and published sequences of 10 genes for 344 tips spanning 88 of 109 brachyuran families. Using 36 newly vetted fossil calibrations, we infer that brachyurans most likely diverged in the Triassic, with family-level splits in the late Cretaceous and early Paleogene. By contrast, the root age is underestimated with automated sampling of 328 fossil occurrences explicitly incorporated into the tree prior, suggesting such models are a poor fit under heterogeneous fossil preservation. We apply recently defined trait-by-environment associations to classify a gradient of transitions from marine to terrestrial lifestyles. We estimate that crabs left the marine environment at least seven and up to 17 times convergently, and returned to the sea from non-marine environments at least twice. Although the most highly terrestrial- and many freshwater-adapted crabs are concentrated in Thoracotremata, Bayesian threshold models of ancestral state reconstruction fail to identify shifts to higher terrestrial grades due to the degree of underlying change required. Lineages throughout our tree inhabit intertidal and marginal marine environments, corroborating the inference that the early stages of terrestrial adaptation have a lower threshold to evolve. Our framework and extensive new fossil and natural history datasets will enable future comparisons of non-marine adaptation at the morphological and molecular level. Crabs provide an important window into the early processes of adaptation to novel environments, and different degrees of evolutionary constraint that might help predict these pathways.

Shift in symbiotic lifestyle as the major process shaping the evolution of pea crabs (Decapoda: Brachyura: Pinnotheroidea).

The pea crabs, superfamily Pinnotheroidea, are exceptional among brachyuran crabs in their diverse symbiotic associations involving both inquilinism and protective symbiosis. While this group presents a rare opportunity for evolutionary comparative study of host switching and morphological evolution in marine macroinvertebrates, previous phylogenetic studies have been focused on systematics. Here, we reconstructed the most extensive phylogeny of Pinnotheroidea based on two mitochondrial and six nuclear markers, with the aim of elucidating the host switching pathways and the correlation between symbiotic lifestyles and selected morphological adaptations. Ancestral state reconstruction of host association revealed a monophyletic origin of symbiosis in the form of inquilinism. Subsequent shifts in microhabitat preference for burrows or worm tubes, and the move to protective symbiosis, primarily in the switch to mollusc endosymbiosis, contributed to radiation in Pinnotheridae. Further parallel colonisations of echinoderms and tunicates occurred but did not lead to extensive diversification, except in the Clypeasterophilus + Dissodactylus lineage, which experienced a unique switch to echinoderm ectosymbiosis. The evolution of the third maxillipeds, carapace shape and ambulatory pereiopods suggests a rather strong coupling with the symbiotic lifestyle (whether inquilinism or protective symbiosis). Phenotypic diversity of these characters was higher among species engaged in protective symbiosis, with convergence in form (or function) among those sharing the same host affiliation. Species having different host affiliations or symbiotic lifestyles might also exhibit convergence in the form of the three morphological traits, suggesting a common adaptive value of the specialisations. Pinnotherid crabs overall exhibited a lower trait diversity than the also symbiotic palaemonid shrimps with comparable species diversity. This may plausibly be attributed to differences in potential for morphological modification to serve additional functions among the traits analysed in the two groups, the less frequent host switching and the less diverse host affiliations, and thus a less complicated evolutionary history in pinnotherids.

Genomic analysis reveals strong population structure in the Giant Sydney Crayfish (Euastacus spinifer (Heller, 1865)).

Australia is home to over 140 species of freshwater crayfish (Decapoda: Parastacidae), representing a centre of diversity for this group in the Southern Hemisphere. Species delimitation in freshwater crayfish is difficult because many species show significant variation in colouration and morphology. This is particularly evident in the genus Euastacus, which exhibits large variations in colour and spination throughout its putative range. To understand this variation, we investigated the genetic diversity, population structure, phylogeny, and evolutionary timescale of the Giant Sydney Crayfish (Euastacus spinifer (Heller, 1865)). Our data set is sampled from over 70 individuals from across the ∼600 km range of the species, and includes a combination of two mitochondrial markers and more than 7000 single-nucleotide polymorphisms (SNPs) from the nuclear genome. Data were also obtained for representatives of the close relative, Euastacus vesper McCormack and Ahyong, 2017. Genomic SNP analyses revealed strong population structure, with multiple distinct populations showing little evidence of gene flow or migration. Phylogenetic analyses of mitochondrial data revealed similar structure between populations. Taken together, our analyses suggest that E. spinifer, as currently understood, represents a species complex, of which E. vesper is a member. Molecular clock estimates place the divergences within this group during the Pleistocene. The isolated and highly fragmented populations identified in our analyses probably represent relict populations of a previously widespread ancestral species. Periodic flooding events during the Pleistocene are likely to have facilitated the movement of these otherwise restricted freshwater crayfish within and between drainage basins, including the Murray-Darling and South East Coast Drainages. We present evidence supporting the recognition of populations in the southern parts of the range of E. spinifer as one or two separate species, which would raise the number of species within the E. spinifer complex to at least three. Our results add to the growing body of evidence that many freshwater crayfish exhibit highly fragmented, range-restricted distributions. In combination with the life-history traits of these species, the restricted distributions exacerbate the threats already placed on freshwater crayfish, which are among the five most endangered animal groups globally.

Plant feeding promotes diversification in the Crustacea.

About half of the world's animal species are arthropods associated with plants, and the ability to consume plant material has been proposed to be an important trait associated with the spectacular diversification of terrestrial insects. We review the phylogenetic distribution of plant feeding in the Crustacea, the other major group of arthropods that commonly consume plants, to estimate how often plant feeding has arisen and to test whether this dietary transition is associated with higher species numbers in extant clades. We present evidence that at least 31 lineages of marine, freshwater, and terrestrial crustaceans (including 64 families and 185 genera) have independently overcome the challenges of consuming plant material. These plant-feeding clades are, on average, 21-fold more speciose than their sister taxa, indicating that a shift in diet is associated with increased net rates of diversification. In contrast to herbivorous insects, most crustaceans have very broad diets, and the increased richness of taxa that include plants in their diet likely results from access to a novel resource base rather than host-associated divergence.

Barcoding and multi-locus phylogeography of the globally distributed calcareous tubeworm genus Hydroides Gunnerus, 1768 (Annelida, Polychaeta, Serpulidae).

Hydroides is a large and diverse group of calcareous tubeworms (Serpulidae, Annelida) recognised by a distinctive but variable two-tiered operculum. Despite considerable research using several species of Hydroides as models in ecological and biofouling studies, phylogenetic and biogeographic relationships within the genus are still poorly understood. Using combined mitochondrial (COI, cytochrome b) and nuclear (18S, 28S and ITS) gene markers for 284 individuals of 45 morphospecies of Hydroides, we investigated the global phylogenetic and biogeographic relationships within the genus. Phylogenetic topologies were well supported and indicated high genetic diversity within Hydroides, revealing potential cryptic species. Present results also include the first COI barcoding data enabling rapid and effective species identification of Hydroides on a global scale. Phylogenetic relationships within Hydroides were more concordant with geographical distributions than morphological similarity of their opercula. Molecular divergence estimates suggested the origin and subsequent diversification in the western Tethys Sea followed by a shift of the historical centre of diversity from the Indo-Mediterranean region to the central Indo-Pacific during the last 50 million years. Further studies on population genetics of species consisting of multiple lineages would provide a better understanding on the status of potential cryptic species. Furthermore, paleogeographic studies based on fossil Hydroides tubes would provide evidence to test this biogeographic hypothesis.

Evolutionary history of true crabs (Crustacea: Decapoda: Brachyura) and the origin of freshwater crabs.

Crabs of the infra-order Brachyura are one of the most diverse groups of crustaceans with approximately 7,000 described species in 98 families, occurring in marine, freshwater, and terrestrial habitats. The relationships among the brachyuran families are poorly understood due to the high morphological complexity of the group. Here, we reconstruct the most comprehensive phylogeny of Brachyura to date using sequence data of six nuclear protein-coding genes and two mitochondrial rRNA genes from more than 140 species belonging to 58 families. The gene tree confirms that the "Podotremata," are paraphyletic. Within the monophyletic Eubrachyura, the reciprocal monophyly of the two subsections, Heterotremata and Thoracotremata, is supported. Monophyly of many superfamilies, however, is not recovered, indicating the prevalence of morphological convergence and the need for further taxonomic studies. Freshwater crabs were derived early in the evolution of Eubrachyura and are shown to have at least two independent origins. Bayesian relaxed molecular methods estimate that freshwater crabs separated from their closest marine sister taxa ~135 Ma, that is, after the break up of Pangaea (∼200 Ma) and that a Gondwanan origin of these freshwater representatives is untenable. Most extant families and superfamilies arose during the late Cretaceous and early Tertiary.

The emergence of lobsters: phylogenetic relationships, morphological evolution and divergence time comparisons of an ancient group (decapoda: achelata, astacidea, glypheidea, polychelida).

Lobsters are a ubiquitous and economically important group of decapod crustaceans that include the infraorders Polychelida, Glypheidea, Astacidea and Achelata. They include familiar forms such as the spiny, slipper, clawed lobsters and crayfish and unfamiliar forms such as the deep-sea and "living fossil" species. The high degree of morphological diversity among these infraorders has led to a dynamic classification and conflicting hypotheses of evolutionary relationships. In this study, we estimated phylogenetic relationships among the major groups of all lobster families and 94% of the genera using six genes (mitochondrial and nuclear) and 195 morphological characters across 173 species of lobsters for the most comprehensive sampling to date. Lobsters were recovered as a non-monophyletic assemblage in the combined (molecular + morphology) analysis. All families were monophyletic, with the exception of Cambaridae, and 7 of 79 genera were recovered as poly- or paraphyletic. A rich fossil history coupled with dense taxon coverage allowed us to estimate and compare divergence times and origins of major lineages using two drastically different approaches. Age priors were constructed and/or included based on fossil age information or fossil discovery, age, and extant species count data. Results from the two approaches were largely congruent across deep to shallow taxonomic divergences across major lineages. The origin of the first lobster-like decapod (Polychelida) was estimated in the Devonian (∼409-372 Ma) with all infraorders present in the Carboniferous (∼353-318 Ma). Fossil calibration subsampling studies examined the influence of sampling density (number of fossils) and placement (deep, middle, and shallow) on divergence time estimates. Results from our study suggest including at least 1 fossil per 10 operational taxonomic units (OTUs) in divergence dating analyses. [Dating; decapods; divergence; lobsters; molecular; morphology; phylogenetics.].

A comprehensive and integrative reconstruction of evolutionary history for Anomura (Crustacea: Decapoda).

BACKGROUND: The infraorder Anomura has long captivated the attention of evolutionary biologists due to its impressive morphological diversity and ecological adaptations. To date, 2500 extant species have been described but phylogenetic relationships at high taxonomic levels remain unresolved. Here, we reconstruct the evolutionary history-phylogeny, divergence times, character evolution and diversification-of this speciose clade. For this purpose, we sequenced two mitochondrial (16S and 12S) and three nuclear (H3, 18S and 28S) markers for 19 of the 20 extant families, using traditional Sanger and next-generation 454 sequencing methods. Molecular data were combined with 156 morphological characters in order to estimate the largest anomuran phylogeny to date. The anomuran fossil record allowed us to incorporate 31 fossils for divergence time analyses. RESULTS: Our best phylogenetic hypothesis (morphological + molecular data) supports most anomuran superfamilies and families as monophyletic. However, three families and eleven genera are recovered as para- and polyphyletic. Divergence time analysis dates the origin of Anomura to the Late Permian ~259 (224-296) MYA with many of the present day families radiating during the Jurassic and Early Cretaceous. Ancestral state reconstruction suggests that carcinization occurred independently 3 times within the group. The invasion of freshwater and terrestrial environments both occurred between the Late Cretaceous and Tertiary. Diversification analyses found the speciation rate to be low across Anomura, and we identify 2 major changes in the tempo of diversification; the most significant at the base of a clade that includes the squat-lobster family Chirostylidae. CONCLUSIONS: Our findings are compared against current classifications and previous hypotheses of anomuran relationships. Many families and genera appear to be poly- or paraphyletic suggesting a need for further taxonomic revisions at these levels. A divergence time analysis provides key insights into the origins of major lineages and events and the timing of morphological (body form) and ecological (habitat) transitions. Living anomuran biodiversity is the product of 2 major changes in the tempo of diversification; our initial insights suggest that the acquisition of a crab-like form did not act as a key innovation.

Munidopsis kareenae, a new species of seamount squat lobster from New Zealand with a key to the New Zealand species of Munidopsis (Crustacea: Decapoda: Munidopsidae).

A new species of the squat lobster genus Munidopsis is described from Nukuhou Seamount, North Island, New Zealand. The new species is allied to members of the "Galathodes group" within Munidopsis that share a flattened, distally trifid rostrum, an unarmed carapace surface (apart from paired epigastric spines in some species), unarmed abdominal tergites and absence of pereopodal epipods. The new species is readily separated from these species by the combination of unarmed lateral carapace margins posterior to the anterolateral spine, absence of epigastric spines, and prominently spinose extensor margins of the pereopod 2-4 meri. Fourteen species of Munidopsis are now recorded from New Zealand; a key to the New Zealand species is provided.

Discovery of a new genus and new species of Indo-West Pacific pilumnoidid crab from a semisubmersible oil platform (Crustacea: Brachyura: Pseudozioidea).

A new genus and new species of pseudozioid crab of the family Pilumnoididae is described from a fouling community on a semisubmersible oil platform in Singapore that had been operating in the Timor Sea and South China Sea. Setozius incertus gen. et sp. nov. superficially resembles species of Pilumnus (Pilumnidae, Pilumnoidea) but has male first and second gonopod structures characteristic of the Pseudozioidea. The form of the carapace, male anterior thoracic sternum and male abdomen indicates that it should be classified in the Pilumnoididae. Setozius is the first member of the family to be recorded from the Indo-West Pacific; all other known pilumnoidids occur in the Atlantic and eastern Pacific.

New species and new records of deepwater munidid squat lobsters from north-western Australia: Onconida, Bathymunida, Crosnierita, Plesionida and Torbenella.

Seven species of Munididae are reported from the continental margin of north-western Australia. Three species are new to science: Crosnierita adela sp. nov., Onconida ariel sp. nov. and Plesionida aurelia sp. nov., each presently known only from Western Australia. Four species are reported for the first time from Australian waters, Bathymunida balssi Van Dam, 1838, Bathymunida dissimilis Baba & de Saint Laurent, 1996, Crosnierita yante (Macpherson, 1994) and Torbenella orbis (Baba, 2005). Keys to the world species of the genera represented are provided.

Parapleisticantha Yokoya, 1933, a valid genus of deep-sea inachid spider crab from Japan and the Philippines (Crustacea: Decapoda: Brachyura: Majoidea), with the description of a new species.

The inachid spider crab genus, Parapleisticantha Yokoya, 1933 [type species: Parapleisticantha japonica Yokoya, 1933] is removed from the synonymy of Pleistacantha Miers, 1879 [type species: Pleistacantha sanctijohannis Miers, 1879], and recognised as a valid genus. Parapleisticantha differs from Pleistacantha sensu stricto primarily by having a less spiny carapace, stouter and more inflated male chelipeds, and by lacking a slender subdistal process on the male first gonopod. We redescribe Parapleisticantha japonica based on the Japanese type material and describe as new a second species, Parapleisticantha ludivinae n. sp., recently discovered in the Philippines.

Morphological and molecular description of the late-stage larvae of Alima Leach, 1817 (Crustacea: Stomatopoda) from Lizard Island, Australia.

Alima pacifica and A. orientalis are stomatopods commonly found at Lizard Island, Great Barrier Reef, Australia. There are currently no descriptions that link the larvae to the adult morphotype despite the frequent occurrence of the last larval stage of these two species. We used DNA barcoding of the cytochrome oxidase I (COI) gene to link the last stage larvae of A. pacifica and A. orientalis to the respective adult morphotype. Detailed morphological descriptions of the late larva of each species are provided and compared to other described last-stage Alima larvae. These data support previous studies that suggest paraphyly of the genus Alima.

Towards an Australian Bioregionalisation Atlas: A provisional area taxonomy of Australia's biogeographical regions.

The large number, definition, varied application and validity of named Australian biogeographical regions reflect their ad hoc development via disparate methods or case study idiosyncracies. They do not represent a coherent system. In order to resolve these uncertainties an Australian Bioregionalisation Atlas is proposed as a provisional hierarchical classification, accounting for all known named areas. This provisional area taxonomy includes a diagnosis, description, type locality and map for each named area within the Australian continent, as well as a first-ever area synonymy. Akin to biological classifications, this Atlas seeks to provision universality, objectivity and stability, such that biogeographers, macroecologists and geographers, can test existing areas as well as proposing novel areas. With such a formalised and comparative system in place, practitioners can analyse the definition and relationships of biotic areas, and putatively minimise ad hoc explanations.

On the identity of Pronotonyx laevis (Miers, 1884) (Crustacea: Brachyura: Pilumnidae).

The poorly known brachyuran crab, Pronotonyx laevis Ward, 1936, from northern Australia, is redescribed based on type and other material. We document adults of both sexes and confirm the taxonomic placement of the Pronotonyx in the Pilumnidae. Pronotonyx is most similar to the Australian Pseudocryptocoeloma parvum Ward, 1936, differing in features of the carapace and pereopods.

Hermit to king, or hermit to all: multiple transitions to crab-like forms from hermit crab ancestors.

The Anomura presents the greatest degree of morphological disparity in the decapod Crustacea, with body forms ranging from the symmetrical and asymmetrical hermit crabs to squat lobsters and king crabs. The phylogeny of the anomurans has been fraught with controversy. Recent debate has focused primarily on the phenomenon of carcinization, the evolution of crab-like form from a non-crab-like ancestor, focused chiefly on derivation of king crabs from asymmetrical hermit crabs--the "hermit to king" hypothesis. We show by phylogenetic analysis of five nuclear protein-coding gene sequences that hermit crabs have a single origin, but surprisingly, that almost all other major clades and body forms within the Anomura, are derived from within the hermit crabs. The crab-like form and squat lobster form have each evolved at least twice from separate symmetrical hermit crab ancestors. In each case, a carcinization trend can be posited via a transition series from the initial symmetrical long-tailed hermit crab form, through the intermediate squat lobster or asymmetrical hermit crab form, to the final crab-like form. Adaptation to dextral shell habitation evolved at least twice, once in an exclusively deep-water clade and once in the common ancestor of all other asymmetrical hermit crabs (from which king crabs are derived). These remarkable cases of parallelism suggest considerable phenotypic flexibility within the hermit crab ground plan, with a general tendency toward carcinization. Rather than having a separate origin from other major clades, hermit crabs have given rise to most other major anomuran body types.

Stomatopod Crustacea of Lord Howe Island.

Prior to the present study, five species in four genera of the mantis shrimp superfamily Gonodactyloidea were known from Lord Howe Island, Australia. The 2017 Australian Museum expedition to Lord Howe Island made a small but significant collection of stomatopods, comprising four species: Chorisquilla tweediei (Serène, 1950), Gonodactylaceus falcatus (Forskål, 1775), Pseudosquilla ciliata (Fabricius, 1787) and a new species of Acaenosquilla, representing the first record of the superfamily Lysiosquilloidea from Lord Howe Island. The new species of Acaenosquilla is formally described and a key to the stomatopods of Lord Howe Island is provided.