Diversification of freshwater crabs on the sky islands in the Hengduan Mountains Region, China

The numerous naturally-fragmented sky islands (SIs) in the Hengduan Mountains Region (HMR) of southwestern China constitute discontinuous landscapes where montane habitats are isolated by dry-hot valleys which have fostered exceptional species diversification and endemicity. However, studies documenting the crucial role of SI on the speciation dynamics of native freshwater organisms are scarce. Here we used a novel set of comprehensive genetic markers (24 nuclear DNA sequences and complete mitogenomes), morphological characters, and biogeographical information to reveal the evolutionary history and speciation mechanisms of a group of small-bodied montane potamids in the genus Tenuipotamon. Our results provide a robustly supported phylogeny, and suggest that the vicariance events of these montane crabs correlate well with the emergence of SIs due to the uplift of the HMR during the Late Oligocene. Furthermore, ancestrally, mountain ridges provided corridors for the dispersal of these montane crabs that led to the colonization of moist montane-specific habitats, aided by past climatic conditions that were the crucial determinants of their evolutionary history. The present results illustrated that the mechanisms isolating SIs are reinforced by the harsh-dry isolating climatic features of dry-hot valleys separating SIs and continue to affect local diversification. This offers insights into the causes of the high biodiversity and endemism shown by the freshwater crabs of the HMR-SIs in southwestern China.

Illegal mining impacts on freshwater Potamonautid crab in a subtropical Austral highland biosphere reserve

The contamination of surface water by heavy metals, especially mercury, has become a global issue. This problem is particularly exacerbated in rivers and reservoirs situated in developing nations. Therefore, the objective of this study was to evaluate the potential contamination effects of illegal gold mining activities on freshwater Potamonautid crabs and to quantify the mercury levels in 49 river sites under three land use classes: communal areas, national parks and timber plantations. We used a combination of field sampling, multivariate analysis and geospatial tools to quantify mercury concentrations in relation to crab abundances. Illegal mining was prevalent throughout the three land use classes, with mercury (Hg) being detected in 35 sites (71.5 %). The mean range of Hg concentrations detected across the three-land uses was: communal areas 0-0.1 mg kg-1, national parks 0-0.3 mg kg-1 and timber plantations 0-0.06 mg kg-1. Mean Hg geo-accumulation index values showed strong to extreme contamination in the national park, with strong contamination observed for communal areas and timber plantations; furthermore, the enrichment factor for Hg concentrations in the communal and national park areas showed extremely high enrichment. Two crab species (i.e., Potamonautes mutareensis, Potamonautes unispinus) were found in the Chimanimani area, with P. mutareensis being the dominant taxon in the region across all the three land use areas. The national parks had higher total crab abundances than communal and timber plantation areas. We observed negative and significant K, Fe, Cu and B effects on total Potamonautid crab abundances, but surprisingly not for other metals such as Hg which might reflect their widespread pollution. Thus, illegal mining was observed to impact the river system, having a serious impact on the crab abundance and habitat quality. Overall, the findings of this study underscores the need to address the issue of illegal mining within the developing world as well as to establish concerted effort from all stakeholders (e.g., government, mining companies, local communities, and civil society groups) to help protect the less charismatic and understudied taxa. In addition, addressing illegal mining and protecting understudied taxa aligns with the SDGs (e.g. SDG 14/15-life below water/life on land) and contributes to global efforts to safeguard biodiversity and promote sustainable development.

Museum DNA reveals a new, potentially extinct species of rinkhals (Serpentes: Elapidae: Hemachatus) from the Eastern Highlands of Zimbabwe

Genetic information plays a pivotal role in species recognition and delimitation, but rare or extinct animals can be difficult to obtain genetic samples from. While natural history wet collections have proven invaluable in the description of novel species, the use of these historical samples in genetic studies has been greatly impeded by DNA degradation, especially because of formalin-fixation prior to preservation. Here, we use recently developed museum genomics approaches to determine the status of an isolated population of the elapid snake genus Hemachatus from Zimbabwe. We used multiple digestion phases followed by single strand sequencing library construction and hybridisation capture to obtain 12S and 16S rDNA sequences from a poorly preserved tissue sample of this population. Phylogenetic and morphological analyses in an integrated taxonomic framework demonstrate that the Zimbabwean rinkhals population represents an old and highly distinct lineage, which we describe as a new species, Hemachatus nyangensis sp. nov. Our phylogenetic dating analysis is compatible with venom spitting having evolved in response to the threat posed by early hominins, although more data are required for a robust test of this hypothesis. This description demonstrates the power of museum genomics in revealing rare or even extinct species: Hemachatus from Zimbabwe are only known from a small area of the Eastern Highlands known for high endemism. No living specimens have been seen since the 1980s, most likely due to dramatic land-use changes in the Eastern Highlands, suggesting that the species could be extinct. In view of its recognition as a highly distinct lineage, urgent action is required to determine whether any populations survive, and to safeguard remaining habitat.

Description of a new montane freshwater crab (Arthropoda, Malacostraca, Decapoda, Potamonautidae) from the Eastern Cape, South Africa

A new species of freshwater crab, Potamonautesamatholesp. nov., is described from the Winterberg-Amathole mountain range in the Eastern Cape Province, South Africa. Morphologically, P.amathole Peer & Gouws, sp. nov. most closely resembles P.tuerkayi but can be distinguished by key morphological characters including the variation in the shape of the subterminal segment of gonopod 2 between both species. Genetically, P.amathole Peer & Gouws, sp. nov. is placed within the clade of small-bodied, mountain-dwelling crabs including P.parvispina, P.parvicorpus, P.brincki, P.tuerkayi, P.baziya, and P.depressus. The new species is found in slow-moving mountain streams and pools at high altitudes. The continued discovery and description of new freshwater crab species reinforces the need for ongoing research, especially in under-sampled regions.

Cryptic and widespread: a recipe for taxonomic misidentification in a freshwater crab species (Decapoda: Potamonautidae:Potamonautes sidneyi) as evident from species delimitation methods

We examined the systematics of a ubiquitously distributed southern African freshwater crab, Potamonautes sidneyi s.l. species complex. Specimens were subjected to DNA sequence analyses of two mitochondrial loci (16S rRNA + COI). We applied three species delimitations methods (ASAP, bGMYC and bPTP) to test their utility in delineating species boundaries in Potamonautes and three additional Afrotropical genera (Liberonautes, Nesonautes and Seychellum). The combined mtDNA dataset retrieved five clades. Clade 1 comprised of P. barbarai, clade 2 comprised of specimens from the interior of the Great Karoo Basin, sister to P. sidneyi s.s. in clade 3. Clade 4 was confined to Eswatini and the Mpumalanga Province of South Africa, and sister to clade 5 that comprised P. danielsi. The three species delimitation methods either over- or underestimated the number of species. Phylogenetically, specimens from the Great Karoo Basin (clade 2) were equidistant to P. sidneyi s.s. and P. perlatus, while the Eswatini and Mpumalanga specimens (clade 4) were sister to P. danielsi. Clades 2 and 4 are herein described as P. karooensis sp. nov. and P. valles sp. nov., respectively.

A new multilocus phylogeny reveals overlooked diversity in African freshwater crabs (Brachyura: Potamoidea): a major revision with new higher taxa and genera

The taxonomy of 185 species of Afrotropical freshwater crabs is revised to conform to the updated phylogenetic relationships within this large assemblage, based on the largest taxonomic sampling to date (that includes almost all genera and 57% of the species). Four DNA loci were sequenced including three mitochondrial loci (COI, 12S rRNA, 16S rRNA) and one nuclear locus (histone 3), and evolutionary relationships were estimated using maximum likelihood and Bayesian approaches. The divergence times of the major clades were estimated with a Yule tree prior and an uncorrelated lognormal relaxed molecular clock. The taxonomic acts proposed here include the recognition of two Afrotropical families of freshwater crabs (Potamonautidae and Deckeniidae) each with two subfamilies. In the revised Potamonautidae, three new tribes and three new genera (Maritimonautes gen. nov., Nesonautes gen. nov., Occidensonautes gen. nov.), are established, three previously published genera are revised and four subgenera are raised to genus (Arcopotamonautes, Lirrangopotamonautes, Longipotamonautes, Rotundopotamonautes). An updated species list and identification keys for the new taxa, revised distribution maps, digital images and illustrations of diagnostic characters are provided.

Habitat requirements affect genetic variation in three species of mayfly (Ephemeroptera, Baetidae) from South Africa

This study investigates genetic diversity in three species of Ephemeroptera, one eurytopic and therefore widespread (Afroptilumsudafricanum) and two stenotopic and thus endemic (Demoreptusnatalensis and Demoreptuscapensis) species, all of which co-occur in the southern Great Escarpment, South Africa. Mitochondrial DNA was analysed to compare the genetic diversity between the habitat generalist and the two habitat specialists. Afroptilumsudafricanum showed no indication of population genetic structure due to geographic location, while both Demoreptus species revealed clear genetic differentiation between geographic localities and catchments, evident from phylogenetic analyses and high F_ST values from AMOVA. In addition, the phylogenetic analyses indicate some deeper haplotype divergences within A.sudafricanum and Demoreptus that merit taxonomic attention. These results give important insight into evolutionary processes occurring through habitat specialisation and population isolation. Further research and sampling across a wider geographic setting that includes both major mountain blocks of the Escarpment and lowland non-Escarpment sites will allow for refined understanding of biodiversity and associated habitat preferences, and illuminate comparative inferences into gene flow and cryptic speciation.

Divergent evolutionary origins and biogeographic histories of two freshwater crabs (Brachyura: Potamonautes) on the West African conveyer belt islands of São Tomé and Príncipe

We examined the colonization history and phylogeographic structure of the two endemic freshwater crab species (Potamonautes margaritarius and P. principe) inhabiting the volcanic islands of São Tomé and Príncipe, respectively, using mitochondrial and nuclear DNA sequence data. All samples were sequenced for the mtDNA COI locus and used in the phylogeographic analyses, while a single specimen per lineage was sequenced for the two remaining loci (16S rRNA and histone 3) and used in the phylogenetic reconstruction. Phylogenetic results reveal that P. principe diverged early within a clade of East/Southern African Potamonautes during the Miocene, while P. margaritarius diverged between the Late Eocene to Early Miocene. Furthermore, the two species are not sister taxa and are distantly related. These results corroborate previously hypothesised independent transoceanic dispersal events that resulted in the establishment of the endemic freshwater crab fauna of the two islands. Within P. margaritarius, we observed two reciprocally monophyletic clades on São Tomé Island. Clade one occurred in the southeast and southwest of the island, while clade two occurred in the northeast and the northwest; the divergence between the latter two clades was estimated to be of Pleistocene age. The two clades within P. margartarius are genetically highly structured and characterised by the absence of shared maternal haplotypes, suggesting possible speciation within P. margartarius. In contrast P. principe exhibits a shallow population genetic structure. Possible mechanisms of colonization and cladogenesis in the two freshwater crabs are discussed.

Ecological Assessment of Two Species of Potamonautid Freshwater Crabs from the Eastern Highlands of Zimbabwe, with Implications for Their Conservation

The spatial ecology of freshwater crabs and their conservation status is largely understudied in Africa. An ecological assessment was conducted at 104 localities in 51 rivers and/or streams in the Eastern Highlands of Zimbabwe whereby the distribution and abundances of freshwater crab species were mapped and the possible drivers of the observed trends in population structure explored. In addition, information on crab utilisation as a food resource by local communities was assessed via face to face interviews across the region. Finally, the conservation status of each species was assessed using the IUCN Red List criteria. Only two crab species Potamonautes mutareensis and Potamonautes unispinus were recorded within the region of study. Potamonautes mutareensis was largely restricted to less impacted environments in the high mountainous river system, whereas P. unispinus was found in low laying areas. In stretches of river where both species were found to co-occur, the species were never sampled from the same site, with P. mutareensis occurring in shallower, faster flowing environments and P. unispinus in deeper, slow flowing sites. Interview results revealed that the local communities, particularly in the southern part of the Eastern Highlands around the Chipinge area, had a considerable level of utilisation (55% of households) on the harvesting of crabs for household consumption during the non-agricultural season (May to September). Results from the IUCN Red List assessment indicate that both species should be considered as "Least Concern". Threats to freshwater crabs in the Eastern Highlands, however, include widespread anthropogenic impacts such as habitat destruction associated with gold and diamond mining, inorganic and organic pollution and possibly exploitation for human consumption. The current study provides important information and insight towards the possible development of a freshwater crab conservation action plan within the region.

Exploring high-mountain limnic faunas: discovery of a novel endemic bivalve species (Sphaeriidae : Pisidium) in the Nepal Himalayas

High-mountain regions are known to harbour considerable biodiversity, although it is not all well known. The terrestrial fauna of the world’s largest mountain range, the Himalayas, has been moderately well studied, but this is not the case with the limnic fauna, and especially molluscs. During intensive malacozoological field surveys conducted over the past 20 years, the bivalve family Sphaeriidae has been studied in Nepal along an elevational gradient from 100 to 4010 m above sea level (a.s.l.). Here we describe a new species of Sphaeriidae, Pisidium alexeii, sp. nov., based on comprehensive molecular phylogenetics, anatomy and shell morphology. The species can be clearly distinguished from all other sphaeriid species occurring in Nepal. A molecular phylogeny based on mitochondrial and nuclear data inferred the oriental biogeographical affinity of the new species. The species is ecologically restricted and only occurs at a few sites between 1010 and 1700 m a.s.l. A review and updated checklist of the sphaeriid fauna of Nepal is provided and biodiversity and biogeographical patterns are discussed.

Genetic and morphological evidence for a new mountain-living freshwater crab species (Decapoda : Potamonautidae : Potamonautes) from the Western Cape province of South Africa

Recent studies in southern Africa have revealed a wealth of novel freshwater crab species in high mountainous regions. In the present study, phylogeographic affinities between two sister mountain-living freshwater crab species (Potamonautes brincki and P. parvicorpus) were examined for novel lineages. Seventy-six crab specimens were collected throughout the Western Cape Province of South Africa and sequenced for the COI locus. Evolutionary relationships were analysed using Bayesian inference, maximum likelihood and maximum parsimony, a haplotype network and analyses of molecular variance (AMOVA). Results revealed three divergent clades. Clade A comprised specimens of P. brincki restricted to the Hottentots Holland; sister to which was Clade B from the Overberg, while Clade C comprised specimens of P. parvicorpus from the Cape Peninsula and adjacent interior. Haplotype networks and AMOVA provide evidence for the absence of gene flow whilst morphology of the male gonopods and the mandibular palp revealed subtle but consistent differences between the three clades. Since Clades A and C represent two described species, P. brincki and P. parvicorpus, respectively, Clade B is herein described as a new species, P. tuerkayi, sp. nov. These results highlight the importance of continued sampling of mountain habitats to document aquatic invertebrate diversity.

Multilocus Phylogeny of the Afrotropical Freshwater Crab Fauna Reveals Historical Drainage Connectivity and Transoceanic Dispersal Since the Eocene

Phylogenetic reconstruction, divergence time estimations and ancestral range estimation were undertaken for 66% of the Afrotropical freshwater crab fauna (Potamonautidae) based on four partial DNA loci (12S rRNA, 16S rRNA, cytochrome oxidase one [COI], and histone 3). The present study represents the most comprehensive taxonomic sampling of any freshwater crab family globally, and explores the impact of paleodrainage interconnectivity on cladogenesis among freshwater crabs. Phylogenetic analyses of the total evidence data using maximum-likelihood (ML), maximum parsimony (MP), and Bayesian inference (BI) produced a robust statistically well-supported tree topology that reaffirmed the monophyly of the Afrotropical freshwater crab fauna. The estimated divergence times suggest that the Afrotropical Potamonautidae diverged during the Eocene. Cladogenesis within and among several genera occurred predominantly during the Miocene, which was associated with major tectonic and climatic ameliorations throughout the region. Paleodrainage connectivity was observed with specimens from the Nilo-Sudan and East African coast proving to be sister to specimens from the Upper Guinea Forests in West Africa. In addition, we observed strong sister taxon affinity between specimens from East Africa and the Congo basin, including specimens from Lake Tanganyika, while the southern African fauna was retrieved as sister to the Angolan taxa. Within the East African clade we observed two independent transoceanic dispersal events, one to the Seychelles Archipelago and a second to Madagascar, while we observe a single transoceanic dispersal event from West Africa to São Tomé. The ancestral area estimation suggested a West African/East African ancestral range for the family with multiple dispersal events between southern Africa and East Africa, and between East Africa and Central Africa The taxonomic implications of our results are discussed in light of the widespread paraphyly evident among a number of genera.