In the biogeographical and taxonomical literature before the 1980s there was a wide perception that widespread, often referred to as ‘cosmopolitan’, species were very common among polychaetes. Here we discuss the origins of this perception, how it became challenged, and our current understanding of marine annelid distributions today. We comment on the presence of widely distributed species in the deep sea and on artificially extended ranges of invasive species that have been dispersed by anthropogenic means. We also suggest the measures needed to revolve the status of species with reported cosmopolitan distributions and stress the value of museum collections and vouchers to be associated with DNA sequences in resolving species distributions.

The genus Dysdera Latreille, 1804, a species-rich group of spiders that includes specialised predators of woodlice, contains several complexes of morphologically similar sibling species. Here we investigate species limits in the D. erythrina (Walckenaer, 1802) complex by integrating phenotypic, cytogenetic and molecular data, and use this information to gain further knowledge on its origin and evolution. We describe 16 new species and redescribe four poorly known species belonging to this clade. The distribution of most of the species in the complex is limited to southern France and the north-eastern Iberian Peninsula. The species studied do not show any obvious differences in habitat preference, and some of them even occur sympatrically at certain sites. They probably feed on the same type of prey as they readily capture woodlice. On the other hand, they differ in body size, mouthparts shape, sculpturing of carapace, morphology of the copulatory organs, karyotype and DNA sequences. Experimental interspecific mating showed a partial precopulatory behavioural barrier between D. erythrina and D. cechica, sp. nov. Our data suggest that karyotype evolution of the complex included chromosome fusions and fissions as well as translocations (between autosomes as well as autosomes and sex chromosomes). We hypothesise that chromosome rearrangements generating reproductive incompatibility played a primary role in speciation within Dysdera complexes. Dysdera spiders are poor dispersers, and their original distribution areas (forested areas in the Mediterranean) were repeatedly fragmented during Quarternary climatic oscillations, facilitating integration of chromosome rearrangements into karyotypes by genetic drift. Sympatric occurrence of closely related species may have been promoted by prey segregation as suggested by differentiation in body size in co-occurring species. The following new species are described: D. catalonica, sp. nov., D. cechica, D. dolanskyi, sp. nov., D. fabrorum, sp. nov., D. garrafensis, sp. nov., D. graia, sp. nov., D. kropfi, sp. nov., D. minairo, sp. nov., D. portsensis, sp. nov., D. pradesensis, sp. nov., D. pyrenaica, sp. nov., D. quindecima, sp. nov., D. septima, sp. nov., D. stahlavskyi, sp. nov., D. tredecima, sp. nov. and D. undecima, sp. nov.

Branchiobdellidans are ectosymbiotic annelids primarily associated with freshwater crayfish. Previous studies of branchiobdellidans in Croatia have been focussed mainly on the distribution and diversity of the genus Branchiobdella Odier, 1823. The objective of the present research was to infer the phylogenetic relationships of branchiobdellidan species living on crayfish from the genus Austropotamobius Skorikow, 1907 from Croatia and surrounding countries, using mitochondrial cytochrome c oxidase subunit I sequences as a molecular marker. Furthermore, the potential coevolution of branchiobdellidans and their crayfish hosts was examined by comparing the results of the phylogenetic analyses of Branchiobdella and Austropotamobius. The analyses included branchiobdellidans collected from 74 populations of Au. torrentium (Schrank, 1803) and Au. pallipes (Lereboullet, 1858), and established the presence of five branchiobdellidan species: Branchiobdella astaci Odier, 1823, B. hexadonta Grüber, 1883, B. italica Canegallo, 1928, B. parasita (Braun, 1805) and B. pentadonta Whitman, 1882. The results of the phylogenetic analyses were congruent with the results of morphological identification, revealing high diversity of the branchiobdellidan fauna in Croatia. High observed intraspecific p-distance values, in some cases exceeding interspecific distances, imply the existence of cryptic taxa. Furthermore, observed congruent phylogenetic patterns within Austropotamobius and within studied branchiobdellidans indicate similar evolutionary histories, implying their coevolution.

Woodroaches from the genus Cryptocercus Scudder, 1862 are known to display low levels of morphological divergence, yet significant genetic divergence and variability in chromosome number. Compared with Cryptocercus taxa from North America, the diversity of the genus in Asia has received relatively little attention. We performed morphological and karyotypic examinations of multiple taxa from several previously unsampled mountainous areas of central and south-western China, and identified nine candidate species primarily on the basis of chromosome number. We then investigated diversity across all Asian Cryptocercus, through phylogenetic analyses of 135 COI sequences and 74 28S rRNA sequences from individuals of 28 localities, including species delimitation analysis in General Mixed Yule Coalescent (GMYC) and Automatic Barcode Gap Discovery (ABGD). Phylogenetic results indicated that individuals from the same locality constituted well supported clades. The congruence of GMYC and ABGD results were in almost perfect accord, with 28 candidate species described on the basis of karyotypes (including the nine identified in this study). We provide evidence that each valley population in the Hengduan Mountains contains a separate evolving lineage. We conclude that the principal cause of the rich Cryptocercus diversity in China has been the uplift of the Qinghai-Tibet Plateau.

Pea crabs of the superfamily Pinnotheroidea De Haan, 1833 are known for their obligate commensal relationships with other marine invertebrates. The concomitant specialisations and adaptations of pinnotheroids have resulted in superficially similar body forms that include a high degree of structural reduction. This has confounded interpretation of their phylogenetic position in the Brachyura and interrelationships within Pinnotheroidea, though all were nevertheless believed to be united by a monophyletic origin of obligate commensalism. The family Aphanodactylidae Ahyong & Ng, 2009 was proposed for a group of genera associated with tube-dwelling polychaetes formerly classified in Pinnotheridae, and provisionally retained in the Pinnotheroidea. We investigated the phylogenetic position of Aphanodactylidae using molecular data from three markers (mitochondrial 12S and 16S rRNAs, and nuclear histone H3) covering five of the 12 described aphanodactylid species and a total of 15 thoracotreme families. We found Aphanodactylidae to be monophyletic, but widely distant from Pinnotheridae and instead most closely related to Macrophthalmidae (Ocypodoidea) and Varunidae (Grapsoidea). Therefore, the family Aphanodactylidae is corroborated, but its placement in Pinnotheroidea is rejected. Instead, the phylogenetic position of Aphanodactylidae, as clearly distant from other pinnotheroids, demonstrates that obligate commensalism has evolved independently multiple times within Thoracotremata.

The early origin and evolutionary radiation of graptolites (Hemichordata : Pterobranchia) is a story told almost entirely in the fossil record, but for four extant species of the genus Rhabdopleura Allman, 1869. Here we report the discovery of a fifth species, Rhabdopleura recondita, sp. nov., at a depth range of 2–70 m from the Adriatic and Ionian Seas, always associated with bryozoans in coralligenous habitats. This is the first pterobranch record in Italian waters, and the second in the Mediterranean Sea. The new species is characterised by: (1) tubaria with smooth creeping tubes adherent to the inside of empty bryozoan zooecia; (2) erect outer tubes with a graptolite, fusellar-like organisation; and (3) zooids that extend from a black stolon, which is free from the creeping tube. Each of the paired feeding arms has two rows of tentacles that do not extend to the arm tip. The distal ends of the arms, the collar and the cephalic shield are replete with black granules. Phylogenetic analyses of individual and concatenated gene sequences of mitochondrial 16S rDNA and nuclear 18S rDNA support the validity of R. recondita as a new species. Finally, we discuss the global biogeographic and habitat distributions of the extant Rhabdopleura representatives.

Among ctenid spiders, ctenines comprise the most diverse subfamily. In this study, a new genus of Cteninae, Spinoctenus, is proposed to include the type species S. yotoco, sp. nov. Ten new species are also described: S. escalerete, S. pericos, S. eberhardi, S. spinosus, S. stephaniae, S. nambi, S. florezi, S. tequendama, S. chocoensis and S. flammigerus. Results of the parsimony and Bayesian phylogenetic analyses using morphological and behavioural characters indicate the monophyly of this genus, closely related to Phoneutria Perty, 1883 and Ctenus Walckenaer, 1805. This genus can be distinguished from the remaining Ctenidae by three unambiguous synapomorphies: embolus with folded process, tegulum with median process, and RTA curved internally close to the cymbium. A dispersal-vicariance biogeographical analysis of the genus in the Andean and Chocó regions indicates the origin of Spinoctenus in the Western and Central Andean Cordilleras. From this region, three events of dispersal occurred to the other regions (one to the Chocó and two to the Eastern Cordillera), which were subsequently followed by three events of vicariance, suggesting that dispersal and vicariance were equally important in shaping the current distribution patterns of Spinoctenus species. The discovery of this new genus containing a large number of new species in the Andean and Chocó regions highlights the current poor knowledge of the Colombian biodiversity.

Species-level taxonomy and phylogeny of two genera of South-East (SE) Asian pachybolid millipedes are analysed with a combination of morphological characters and DNA sequences (two mitochondrial gene fragments: COI and 16S rRNA). Strong support is found for the genera Litostrophus Chamberlin, 1921 and Atopochetus Attems, 1953 and for a clade consisting of Litostrophus Atopochetus. Four species of Litostrophus are recognised and (re)described: L. segregatus Chamberlin, 1921 (type species of the genus), L. scaber (Verhoeff, 1938), comb. nov., L. chamaeleon, sp. nov. and L. saraburensis, sp. nov. The genus Tonkinbolus Verhoeff, 1938 (type species T. scaber Verhoeff, 1938) is synonymised under Litostrophus. Atopochetus (type species A. rubropunctatus Attems, 1953), hitherto considered a dubious synonym of Aulacobolus Pocock, 1903, is re-instated for several species until now placed in Tonkinbolus and seven new species. All in all, 10 species of Atopochetus are (re)described: A. dollfusii (Pocock, 1893) (= Aulacobolus rubropunctatus Attems, 1938, syn. nov.), A. moulmeinensis (Pocock, 1893), A. sumatranus (Carl, 1906) (= Trachelomegalus laciniatus Attems, 1937, syn. nov.), A. anaticeps, sp. nov., A. helix, sp. nov., A. setiferus, sp. nov., A. spinimargo, sp. nov., A. truncatus, sp. nov., A. uncinatus, sp. nov. and A. weseneri, sp. nov. Three species recently included in Tonkinbolus are left incertae sedis because they are based exclusively on female type specimens: Spirobolus capucinus Porat, 1896, S. caudulanus Karsch, 1881 and S. macrurus Pocock, 1893. The results of the DNA analysis (COI and 16S rRNA) are congruent with morphological (gonopodal) characters in terms of delimitation of species of Litostrophus and Atopochetus. This is the first DNA study of SE Asian Pachybolidae and as such it provides a basis for further evolutionary and biogeographic studies of SE Asian millipedes.

Parasesarma semperi (Bürger, 1893) was first described from Bohol in the Philippines and is considered to be widely distributed in Southeast Asia. Parasesarma longicristatum (Campbell, 1967) was originally described as a subspecies of P. semperi from Queensland, Australia, and later recognised as a full species. In this study, we re-examine specimens of the two species from across their entire geographic range using genetic markers, a morphometric analysis, and traditional morphological characters. Previous taxonomic species diagnoses were found to be unreliable, but morphometric principle component analyses consistently separate the two species, with the length to width ratio of the propodus of the fourth pereiopod being of particular importance. Genetic data corresponding to the mitochondrial genes COI, ND1 and 16S confirmed a close sister relationship between the two species, forming reciprocally monophyletic groups. Both species have high haplotype diversities and high intraspecific gene flow.

The Indo-Pacific genus Metopograpsus belongs to the family Grapsidae and comprises six species of intertidal crabs inhabiting sheltered rocky shores and mangrove forests. All species are opportunistic feeders and four of them are associated with roots and trunks of mangroves. So far, no comprehensive molecular phylogenetic study has been conducted on this genus, despite the fact that some species are not easily separable from a morphological point of view. We performed a phylogenetic and phylogeographic investigation based on sequences corresponding to both ribosomal mitochondrial DNA genes from 44 samples of Metopograpsus spp., covering the distribution ranges of each species. Our main aims were to validate species identification across their respective distribution ranges and depict the phylogeographic patterns within each species. Our phylogenetic inference reconstructions confirmed monophyly of the six species. We also recorded a high intraspecific genetic variation and strong phylogeographic structure within M. thukuhar and M. quadridentatus. This indicates the occurrence of distinct evolutionarily significant units within these two taxa, possibly corresponding to undescribed species. Further nuclear DNA-based phylogeographic analyses, as well as morphological investigations, will be necessary to assign a taxonomic value to the recorded evolutionarily significant units.

Syllid annelids from the so-called ‘ribbon clade’ are flattened, ribbon-shaped worms of the genera Parahaplosyllis Hartmann-Schröder, 1990, Eurysyllis Ehlers, 1864, Xenosyllis Marion & Bobretzky, 1875, Trypanosyllis Claparède, 1864, Ramisyllis Glasby, Schroeder & Aguado, 2012, Trypanobia Imajima & Hartman, 1964, Plakosyllis Hartmann-Schröder, 1956, Pseudosyllis Grube, 1863 and Trypanedenta Imajima & Hartman, 1964. Some species possess a remarkable reproductive strategy using multiple stolons that has been recently suggested to be ancestral to the group. Here, to evaluate the evolution of reproductive modes in the group, we assess, for the first time, the phylogenetic relationships within the ribbon clade and related genera. We collected new material of Trypanobia and Trypanosyllis from Japan, Spain, Philippines and Indonesia and sequenced it for the nuclear markers 18S rRNA and the mitochondrial markers 16S rRNA and cytochrome c oxidase I for phylogenetic inference and also performed ancestral character reconstruction for the reproductive strategy in the entire group. Formal taxonomic descriptions of a new genus and six new species are provided. The new genus, Trypanospina, gen. nov., is characterised by the spines that cover its surface. Most genera within the ‘ribbon clade’ are monophyletic and the relationships appeared well supported in most cases. However, our phylogenetic hypotheses are not conclusive in regard to the relationships of the genera Trypanedenta and Trypanobia, nor to the status of those to genera as distinctive, since they seem to be paraphyletic and they appear in low-supported clades. In contrast, our results shed light on the evolution of the reproductive modes within the group, showing that scissiparity (development of a single stolon each time) is the ancestral character for the entire group and gemmiparity (development of more than one stolon at the same time) then appeared twice in two independent clades.