The crabs of the family Pinnotheridae are well known as commensals or parasites, mainly of molluscs and tubeworms. The phylogeny of the group, however, is poorly understood, with preliminary morphological and molecular studies questioning its monophyly. Here we used molecular genetic markers (16S, 12S mitochondrial; histone 3 nuclear) to infer a phylogeny for the family Pinnotheridae De Haan, 1833 to reevaluate the phylogeny and systematics at the level of its subfamilies and genera. Our molecular phylogeny indicated that Parapinnixa cortesi Thoma, Heard, & Vargas, 2005, Parapinnixa hendersoni Rathbun, 1918, Pinnotherelia laevigata H. Milne Edwards & Lucas, 1844, Sakaina yokoyai (Glassell, 1933), Tetrias fischerii (A. Milne-Edwards, 1867) and Tetrias scabripes Rathbun, 1898 should be removed from the family Pinnotheridae, while composition of the present subfamilies, Pinnotherinae De Haan, 1833 and Pinnothereliinae Alcock, 1900, must be revised. At generic level, Clypeasterophilus Campos, 1990, Dissodactylus Smith, 1870, Fabia Dana, 1851, Nepinnotheres Manning, 1993 and Pinnixa White, 1846 were not monophyletic in our analyses. With the exclusion of Pinnotherelia from Pinnotheridae, remaining species of Pinnothereliinae are assigned to Pinnixinae Števčić, 2005, a new subfamily based upon revision and elevation of rank for the tribe Pinnixini Števčić, 2005. In addition, we restructure membership of the subfamily Pinnotherinae and propose Pinnixulalinae, subfam. nov. to accommodate species that were excluded by molecular analyses from the other two subfamilies. These have a firm, wider-than-long carapace with clearly defined regions, strong legs that are usually tuberculate and very setose, and a third maxilliped with an elongate ischiomerus in which the ischium and merus may or may not be indistinguishably fused. Our analyses included 169 pinnotherid exemplars, representing almost half of the genera and about a quarter of the species presently recognised for the family. The relationships within and among some taxa are resolved to greater or lesser extent and the phylogenetic biodiversity of pinnotherid crabs is revealed. However, future publications will most likely result in a further increase in the number of taxa.

Spatial isolation and geological history are important factors in the diversification and population differentiation of species. Here we describe distributional patterns of ants in the genus Acropyga across Papua New Guinea (PNG), a highly biodiverse but little-studied region. We estimate phylogenetic relationships among currently recognised species of Acropyga and assess population genetic structure of the widespread species, A. acutiventris, across lowland areas of the island. We find that species of Acropyga present in PNG diversified during the Pliocene, between six and two million years ago. Most species now exhibit a patchy distribution that does not show a strong signal of geological history. However, the population genetic structure of the widespread species A. acutiventris has been influenced by geography, habitat association and, possibly, historical habitat fragmentation. There is a significant effect of isolation-by-distance within continuous lowland forest, and proximity to Australia has had a larger impact in structuring populations of A. acutiventris in PNG than has the Central Papuan Cordillera. This study is the first to describe population genetic patterns of an ant species in Papua New Guinea.

Hydroides brachyacantha Rioja, 1941, an important fouling serpulid species originally described from Mazatlán (Southern Gulf of California, Mexico) and Acapulco (southern Mexican Pacific), has been reported from the Mexican Pacific and numerous tropical and subtropical localities. However, a recent description of H. amri Sun, Wong, ten Hove, Hutchings, Williamson & Kupriyanova, 2015 from Australia, which was historically misidentified as H. brachyacantha, suggested that the widespread ‘H. brachyacantha’ is indeed a species complex. To test the status of H. amri, we conducted phylogenetic analyses based on a combined dataset of 18S rRNA, internal transcribed spacer-2, and cytochrome b sequences of H. brachyacantha from the type locality in Mexico with those of H. amri from Australia. Our molecular data supported the morphology-based hypothesis of H. amri and H. brachyacantha sensu stricto as two distinct species. Furthermore, H. amri comprises two non-sister well-supported clades. Hydroides amri thus comprises what we consider two cryptic species with long-term isolation. Here we describe the genetic lineage in South Australia as Hydroides nikae, sp. nov. Given the absence of a holotype of H. brachyacantha, we designate a neotype collected from the type locality (Mazatlán, Mexico). This study calls for a worldwide revision of the H. brachyacantha-complex.

Cryptic lineages present major challenges for evolutionary and conservation studies, particularly where these lineages remain undiscovered. Freshwater crabs are known to harbour cryptic diversity, in most cases with limited morphological differences. During the present study, we used a multilocus (12S rRNA, 16S rRNA, COI, 28S rRNA, DecapANT and PEPCK) Bayesian species delimitation to examine cryptic diversity within a freshwater crab species complex (Potamonautes clarus/P. depressus). We sampled 25 highland rivers in the Tugela and uMkomazi River drainage systems of the Drakensberg Mountain range, in the KwaZulu–Natal province of South Africa. Our results showed there to be at least eight lineages: six novel potamonautid freshwater crabs, and two described taxa P. clarus and P. depressus. Divergence from the most recent common ancestor occurred between the mid- and late Miocene (12.1 Mya), while divergence within the species complex occurred ∼10.3 Mya up until the Holocene (0.11 Mya). The discovery of six novel lineages of freshwater crabs from a seemingly restricted distribution range has conservation implications, but to date most conservation planning strategies have focussed on freshwater vertebrates. By conducting a fine-scale phylogenetic survey using invertebrates, this study provides a platform for the inclusion of freshwater invertebrates in future conservation assessments.

Fully troglobitic pseudoscorpions are rare in the Afrotropical Region, and we explored the identity and phylogenetic relationships of specimens of a highly modified troglobite of the family Gymnobisiidae in the dark zone of the Wynberg Cave system, on Table Mountain, South Africa. This large pseudoscorpion – described as Gymnobisium inukshuk Harvey & Giribet, sp. nov. – lacks eyes and has extremely long appendages, and has been found together with other troglobitic fauna endemic only to this cave system. Phylogenetic analyses using the nuclear ribosomal genes 18S rRNA and 28S rRNA and the mitochondrial protein-encoding gene cytochrome c oxidase subunit I unambiguously place the new species with other surface Gymnobisium from South Africa. This placement receives strong support and is stable to analytical treatments, including static and dynamic homology, parsimony and maximum likelihood, and data removal for ambiguously aligned sites. This species is the first troglobitic species of the family and one of the most highly modified pseudoscorpions from the Afrotropical Region.

The Indo-Pacific is an extremely large marine realm that unites two oceans via a restricted Coral Triangle corridor, which was historically subjected to lowered sea levels during global glaciation. Although a strong phylogeographic focus on the Central and West Pacific has produced a large body of research, the Indian Ocean has been largely neglected. This may have serious consequences, because the Indian Ocean hosts a large number of marine centres of endemism, yet a large number of nations rely on its marine resources. We examine reasons for this neglect and review what is known about this region and its connectivity to the Indo-West Pacific. We draw attention to the ‘Leeuwin Effect’, a phenomenon where the southward flow of the Leeuwin Current is responsible for transporting larval propagules from the Coral Triangle region down the coast of Western Australia, resulting in broader Indo-West Pacific rather than Indian Ocean affinities. Given challenges in accessing infrastructure and samples, collaboration will inevitably be key to resolving data gaps. We challenge the assumption that the peak of shallow-water marine biodiversity is solely centred in the Coral Triangle, and raise awareness of a seemingly forgotten hypothesis promoting a secondary peak of biodiversity in the western Indian Ocean.