Nuanced impacts of the invasive aquatic plant Crassula helmsii on Northwest European freshwater macroinvertebrate assemblages

Invasive alien species are considered one of the greatest threats to global biodiversity, and are particularly problematic in aquatic systems. Given the foundational role of macrophytes in most freshwaters, alien aquatic plant invasions may drive strong bottom-up impacts on recipient biota. Crassula helmsii (New Zealand pygmyweed) is an Australasian macrophyte, now widespread in northwest Europe. Crassula helmsii rapidly invades small lentic waterbodies, where it is generally considered a serious threat to native biodiversity. The precise ecological impacts of this invasion remain poorly understood, however, particularly with respect to macroinvertebrates, which comprise the bulk of freshwater faunal biodiversity. We conducted a field study of ponds, ditches and small lakes across the core of C. helmsii's invasive range (United Kingdom, Belgium and the Netherlands), finding that invaded sites had higher macroinvertebrate taxon richness than uninvaded sites, and that many infrequent and rare macroinvertebrates co-occurred with C. helmsii. Alien macroinvertebrates were more abundant in C. helmsii sites, however, particularly the North American amphipod Crangonyx pseudogracilis. At the order level, water beetle (Coleoptera) richness and abundance were higher in C. helmsii sites, whereas true fly (Diptera) abundance was higher in uninvaded sites. Taxonomic and functional assemblage composition were both impacted by invasion, largely in relation to taxa and traits associated with detritivory, suggesting that the impacts of C. helmsii on macroinvertebrates are partly mediated by the availability and palatability of its detritus. The nuanced effects of C. helmsii on macroinvertebrates found here should encourage further quantitative research on the impacts of this invasive plant, and perhaps prompt a more balanced re-evaluation of its effects on native aquatic macrofauna.

Water beetles (Coleoptera) associated with Afrotemperate Forest patches in the Garden Route National Park, South Africa

Southern Afrotemperate Forest is concentrated in the southern Cape region of South Africa and whilst it is relatively well known botanically, the fauna, specifically the aquatic invertebrate fauna, is poorly documented. The majority of remaining intact forest habitat is contained within the Garden Route National Park (GRNP), which straddles the provincial boundary between the Western and Eastern Cape. This study undertakes a survey of the water beetle fauna inhabiting the GRNP. The aquatic ecosystems within temperate forests of the region are poorly researched from an ecological and biodiversity perspective, despite being known to harbour endemic invertebrate elements. We collected water beetles and in situ physico-chemical data from a total of 31 waterbodies across the park over two seasons (summer and late winter) in 2017. The waterbodies sampled were mostly small freshwater perennial streams and isolated forest ponds. A total of 61 beetle taxa was recorded (29 Adephaga, 32 Polyphaga) from these waterbodies. The water beetle fauna of these forests appears to be diverse and contains many species endemic to the fynbos-dominated Cape Floristic Region, but very few of the species appear to be forest specialists. This is in contrast to the fynbos heathland habitat of the region, which harbours a high number of water beetle species endemic to this habitat, often with Gondwanan affinity. Our study is the first to document the water beetles of Afrotemperate Forests in the southern Cape region and provides an important baseline for future work on such habitats in the region and in other parts of southern Africa.

Eupotemus tuberculatus sp. nov., the first hooded shore beetle confirmed from southern Africa (Coleoptera, Epimetopidae)

Eupotemus tuberculatus sp. nov. is described on the basis of two specimens discovered during recent field work in South Africa. This is the first member of the Epimetopidae to be confirmed in Africa south of the Congo Basin and Tanzania. The new species is a member of the Eupotemus carinaticollis Fikek et al., 2021 species group, sharing features of pronotal and aedeagal design. Characters distinguishing the new species from previously described taxa are discussed and notes provided on the collecting circumstances.

Science paper or big data? Assessing invasion dynamics using observational data

Non-native species are spreading at an unprecedented rate over large spatial scales, with global environmental change and growth in commerce providing novel opportunities for range expansion. Assessing the pattern and rate of spread is key to the development of strategies for safeguarding against future invasions and efficiently managing existing ones. Such assessments often depend on spatial distribution data from online repositories, which can be spatially biased, imprecise, and lacking in quantity. Here, the influence of disparities between occurrence records from online data repositories and what is known of the invasion history from peer-reviewed published literature on non-native species range expansion was evaluated using 6693 records of the Pacific oyster, Magallana gigas (Thunberg, 1793), spanning 56 years of its invasion in Europe. Two measures of spread were calculated: maximum rate of spread (distance from introduction site over time) and accumulated area (spatial expansion). Results suggest that despite discrepancies between online and peer-reviewed data sources, including a paucity of records from the early invasion history in online repositories, the use of either source does not result in significantly different estimates of spread. Our study significantly improves our understanding of the European distribution of M. gigas and suggests that a combination of short- and long-range dispersal drives range expansions. More widely, our approach provides a framework for comparison of online occurrence records and invasion histories as documented in the peer-reviewed literature, allowing critical evaluation of both data sources and improving our understanding of invasion dynamics significantly.

A revision of Delevea Reichardt, 1976: a Southern African endemic water beetle genus including the largest known extant myxophagans (Coleoptera: Myxophaga: Torridincolidae)

The Southern African endemic torridincolid water beetle genus Delevea Reichardt, 1976 is revised, based largely on recently collected material from the Republic of South Africa. Significant range extensions are provided for the two previously described species, Delevea bertrandi Reichardt, 1976 and D. namibiensis Endrödy-Younga, 1997, these taxa apparently being endemic to the Fynbos Biome in the Western Cape Province and semi-arid, summer rainfall, areas of the Great Escarpment in Namibia and South Africa, respectively. In addition, two new species, Delevea madiba sp. nov. and D. namaqua sp. nov. are described from winter rainfall areas of Namaqualand in the Northern Cape Province. Both species are currently only known from their type locality and, at up to 2.85 mm in adult body length, D. namaqua sp. nov. is the largest described extant species of the suborder Myxophaga.

Ecological niche modeling of the Macedonian mouse, Mus macedonicus (Mammalia, Rodentia), under climate change conditions

Mus macedonicus Petrov & Ružic, 1983, also known as the Macedonian mouse or Balkan short-tailed mouse, lives in the southern Balkans and the Middle East. While this species is common in Mediterranean ecosystems and is listed as “least concern” by the IUCN, little is known about how its distribution may shift with climate change. This study explores the ‘species’ potential distribution in three different periods: during the Last Glacial Maximum (LGM) and under current and future climate scenarios, using Maximum Entropy modelling. Modelling was based on 137 georeferenced occurrence records from Macedonia, Bulgaria, Greece, Turkey, Syria, Lebanon, Israel, Iran, Georgia, and Russia and ten bioclimatic variables from the WorldClim database. We show that a combination of precipitation and temperature variables appear to shape the geographical range of the Macedonian mouse and that its predicted distribution during the LGM is consistent with its survival in multiple refugia, as suggested by previous genetic studies. Modelled future distributions are subtly but significantly different from the current, with population losses and gains in different regions. Our results provide a sound framework for future studies on this model species’ range dynamics, suggesting that the overall geographical range of M. macedonicus is relatively stable in the long term.

The complete mitochondrial genome of Talpa martinorum (Mammalia: Talpidae), a mole species endemic to Thrace: genome content and phylogenetic considerations

The complete mitogenome sequence of Talpa martinorum, a recently described Balkan endemic mole, was assembled from next generation sequence data. The mitogenome is similar to that of the three other Talpa species sequenced to date, being 16,835 bp in length, and containing 13 protein-coding genes, two ribosomal RNA genes, 22 transfer RNA genes, an origin of L-strand replication, and a control region or D-loop. Compared to other Talpa mitogenomes sequenced to date, that of T. martinorum differs in the length of D-loop and stop codon usage. TAG and T-- are the stop codons for the ND1 and ATP8 genes, respectively, in T. martinorum, whilst TAA acts as a stop codon for both ND1 and ATP8 in the other three Talpa species sequenced. Phylogeny reconstructions based on Maximum Likelihood and Bayesian inference analyses yielded phylogenies with similar topologies, demonstrating that T. martinorum nests within the western lineage of the genus, being closely related to T. aquitania and T. occidentalis.

A new species of Protozantaena Perkins, 1997 from the Great Escarpment of South Africa (Coleoptera, Hydraenidae)

Protozantaena birdi sp. nov. is described, based on specimens collected from the Compassberg and Winterberg ranges in the Eastern Cape Great Escarpment, South Africa; the seventh known species of the genus. Morphologically, the new species appears closely related to P. labrata Perkins, 1997, described from the Naukluft Range in the Central Namibian Great Escarpment. Both species live in the margins of small streams in open, semi-arid landscapes.

Plasticity of thermal performance curves in a narrow range endemic water beetle

Thermal history can plastically alter the response of ectotherms to temperature, and thermal performance curves (TPCs) are powerful tools for exploring how organismal-level performance varies with temperature. Plasticity in TPCs may be favoured in thermally variable habitats, where it can result in fitness benefits. However, thermal physiology remains insufficiently studied for freshwater insects despite freshwater biodiversity being at great risk under global change. Here, we assess how acclimation at either summer or winter average temperatures changes TPCs for locomotion activity and metabolism in Enochrus jesusarribasi (Hydrophilidae), a water beetle endemic to shallow saline streams in SE Spain. This beetle is a bimodal gas exchanger and so we also assessed how aerial and aquatic gas exchange varied across temperatures for both acclimation treatments. Responses of locomotory TPCs to thermal acclimation were relatively weak, but high temperature acclimated beetles tended to exhibit higher maximum locomotor activity and reduced TPC breadth than those acclimated at lower temperature. High temperature acclimation increased the thermal sensitivity of metabolic rates, contrary to the response generally found in aquatic organisms. Higher metabolic rates upon high temperature acclimation were achieved by increasing aerial, rather than aquatic oxygen uptake. Such plastic respiratory behaviour likely contributed to enhanced locomotor performance at temperatures around the optimum and thermal plasticity could thus be an important component in the response of aquatic insects to climate change. However, high temperature acclimation appeared to be detrimental for locomotion in subsequent exposure at upper sublethal temperatures, suggesting that this narrow range endemic may be vulnerable to future climate warming. This study demonstrates that TPCs are context-specific, differing with performance metric as well as thermal history. Such context dependency must be considered when using TPCs to predict organismal responses to climate change.

Riberazantaena, a new hydraenid genus from the Eastern Arc Mountains of Tanzania (Coleoptera, Hydraenidae)

A new genus, Riberazantaena gen. nov., is erected to accommodate Protozantaena grebennikovi Perkins, 2009 and Riberazantaena latissima sp. nov. from the South Pare Mountains in Tanzania. Both species are apparently endemic to Eastern Arc mountain forests, adults living terrestrially in damp leaf litter. Protozantaena Perkins, 1997 is redefined in light of the description of the new genus, and a revised key to genera of Parhydraenini is provided.

Taxonomic revision of the Afrotropical Agabus raffrayi species group with the description of four new species (Coleoptera, Dytiscidae)

We revise the Afrotropical Agabus raffrayi species group, motivated by the discovery of new diversity in Kenya and South Africa. Whilst Agabus is mainly a holarctic genus, the Agabus raffrayi group is restricted to high altitude regions of eastern Africa and temperate parts of South Africa, from where we describe the southernmost Agabus in the world. The following new species are introduced: Agabus anguluverpus sp. nov. from Mount Kenya in central Kenya, Agabus austellus sp. nov. a widespread species in South Africa, Agabus riberae sp. nov. from the Kamiesberg and northeastern Cederberg ranges in the Northern and Western Cape Provinces of South Africa and Agabus agulhas sp. nov. from the Agulhas Plain, Western Cape Province, South Africa. We provide a distribution map, a determination key for males, quantitative measurements of diagnostic characters, habitus photos and detailed photos of male genitalia for all described species in the group, as well as images of diagnostic characters and habitats. The presence or absence of an elongated section between the subapical broadening and the base of the apical and subapical teeth of the male aedeagus is a useful novel character, first revealed by our study. In contrast with the most recent revision of Afrotropical Agabus, we show that Agabus ruwenzoricus Guignot, 1936 is restricted to eastern Africa; South African records of this species having been based on misidentifications, no species of the group being common to southern and eastern Africa. We speculate that the raffrayi group may display phylogenetic niche conservatism, being restricted, as an originally temperate taxon, to higher elevations in tropical eastern Africa, but occurring at lower altitudes in temperate South Africa.

Universal metabolic constraints shape the evolutionary ecology of diving in animals

Diving as a lifestyle has evolved on multiple occasions when air-breathing terrestrial animals invaded the aquatic realm, and diving performance shapes the ecology and behaviour of all air-breathing aquatic taxa, from small insects to great whales. Using the largest dataset yet assembled, we show that maximum dive duration increases predictably with body mass in both ectotherms and endotherms. Compared to endotherms, ectotherms can remain submerged for longer, but the mass scaling relationship for dive duration is much steeper in endotherms than in ectotherms. These differences in diving allometry can be fully explained by inherent differences between the two groups in their metabolic rate and how metabolism scales with body mass and temperature. Therefore, we suggest that similar constraints on oxygen storage and usage have shaped the evolutionary ecology of diving in all air-breathing animals, irrespective of their evolutionary history and metabolic mode. The steeper scaling relationship between body mass and dive duration in endotherms not only helps explain why the largest extant vertebrate divers are endothermic rather than ectothermic, but also fits well with the emerging consensus that large extinct tetrapod divers (e.g. plesiosaurs, ichthyosaurs and mosasaurs) were endothermic.

Do differences in developmental mode shape the potential for local adaptation?

Future climate change is leading to the redistribution of life on Earth as species struggle to cope with rising temperatures. Local adaptation allows species to become locally optimized and persist despite environmental selection, but the extent to which this occurs in nature may be limited by dispersal and gene flow. Congeneric marine gastropod species (Littorina littorea and L. saxatilis) with markedly different developmental modes were collected from across a latitudinal thermal gradient to explore the prevalence of local adaptation to temperature. The acute response of metabolic rate (using oxygen consumption as a proxy) to up-ramping and down-ramping temperature regimes between 6°C and 36°C was quantified for five populations of each species. The highly dispersive L. littorea exhibited minimal evidence of local adaptation to the thermal gradient, with no change in thermal optimum (T_opt ) or thermal breadth (T_br ) and a decline in maximal performance (_max ) with increasing latitude. In contrast, the direct developing L. saxatilis displayed evidence of local optimization, although these varied idiosyncratically with latitude, suggesting a suite of selective pressures may be involved in shaping thermal physiology in this relatively sedentary species. Our results show that the biogeography of thermal traits can differ significantly between related species, and show that interpopulation differences in thermal performance do not necessarily follow simple patterns that may be predicted based on latitudinal changes in environmental temperatures. Further research is clearly required to understand the mechanisms that can lead to the emergence of local adaptation in marine systems better and allow improved predictions of species redistribution in response to climate change.

Two new Mesoceration Janssens, 1967 from the Piketberg, South Africa (Coleoptera, Hydraenidae)

Mesoceration explanatum sp. nov. and M. piketbergense sp. nov. are described from the Piketberg range in the Western Cape Province, South Africa, bringing the total number of known species in the genus to 55, all of which are endemic to South Africa. M. explanatum sp. nov. is a member of the truncatum group, whilst M piketbergense sp. nov. belongs to the endroedyi group and is apparently closely related to M. concessum Perkins Balfour-Browne, 1994 and M. tabulare Perkins, 2008, both of which are endemic to the Cape Peninsula. The two new species were both relatively abundant in the Piketberg, and may be narrowly endemic to this inselberg-like mountain range.

Water Beetles as Models in Ecology and Evolution

Beetles have colonized water many times during their history, with some of these events involving extensive evolutionary radiations and multiple transitions between land and water. With over 13,000 described species, they are one of the most diverse macroinvertebrate groups in most nonmarine aquatic habitats and occur on all continents except Antarctica. A combination of wide geographical and ecological range and relatively accessible taxonomy makes these insects an excellent model system for addressing a variety of questions in ecology and evolution. Work on water beetles has recently made important contributions to fields as diverse as DNA taxonomy, macroecology, historical biogeography, sexual selection, and conservation biology, as well as predicting organismal responses to global change. Aquatic beetles have some of the best resolved phylogenies of any comparably diverse insect group, and this, coupled with recent advances in taxonomic and ecological knowledge, is likely to drive an expansion of studies in the future.

A new species of Leielmis Delève, 1964, with a revised key to members of the genus (Coleoptera: Elmidae)

The genus Leielmis was recently revised by Bilton (2017), who established the identity of the type species Leielmis georyssoides (Grouvelle, 1890), and described two new taxa: Leielmis gibbosus Bilton, 2017, widespread in the Cape Fold Mountains and Leielmis hirsutus Bilton, 2017, known to date only from a single site at high altitude in the Groote Winterhoek mountains. A distinctive new species of Leielmis was discovered in a high altitude stream in 2017 in the Hexrivierberge, being collected whilst the generic revision was in press! This species is described below, and a modified key to Leielmis species presented. In light of this discovery it appears likely that further work at high altitude will reveal additional species in the Cape.

Does plasticity in thermal tolerance trade off with inherent tolerance? The influence of setal tracheal gills on thermal tolerance and its plasticity in a group of European diving beetles

In the face of global warming, both the absolute thermal tolerance of an ectotherm, and its ability to shift its tolerance level via acclimation, are thought to be fundamentally important. Understanding the links between tolerance and its plasticity is therefore critical to accurately predict vulnerability to warming. Previous studies in a number of ectotherm taxa suggest trade-offs in the evolution of thermal tolerance and its plasticity, something which does not, however, apply to Deronectes diving beetles, where these traits are instead positively correlated. Here we revisit the relationship between thermal tolerance and plasticity in these beetles, paying attention to a recently discovered morphological adaptation supporting under water respiration - setal tracheal gills. Hollow setae on the elytra interconnect with the beetle's tracheal system, providing a gas exchange surface that allows oxygen to be extracted directly from the water. This enables individuals to stay submerged for longer than their subelytral air stores would allow. We show that hypoxia reduced heat tolerance, especially when individuals were denied access to air, forcing them to rely solely on aquatic gas exchange. Species with higher densities of these gas-exchanging setae exhibited improved cold tolerance, but reduced heat tolerance and lower plasticity of heat tolerance. Differences in setal tracheal gill density across species were also related to habitat use: species with low gill density were found mainly in intermittent, warmer rivers, where underwater gas exchange is more problematic and risks of surfacing may be smaller. Moreover, when controlling for differences in gill density we no longer found a significant relationship between heat tolerance and its plasticity, suggesting that the previously reported positive relationship between these variables may be driven by differences in gill density. Differences in environmental conditions between the preferred habitats could simultaneously select for characteristic differences in both thermal tolerance and gill density. Such simultaneous selection may have resulted in a non-causal association between cold tolerance and gill density. For heat tolerance, the correlations with gill density could reflect a causal relationship. Species relying strongly on diffusive oxygen uptake via setal tracheal gills may have a reduced oxygen supply capacity and may be left with fewer options for matching oxygen uptake to oxygen demand during acclimation, which could explain their reduced heat tolerance and limited plasticity. Our study helps shed light on the mechanisms that underpin thermal tolerance and plasticity in diving air-breathing ectotherms, and explores how differences in thermal tolerance across species are linked to their selected habitat, morphological adaptations and evolutionary history.

Micro-habitat distribution drives patch quality for sub-tropical rocky plateau amphibians in the northern Western Ghats, India

The importance of patch quality for amphibians is frequently overlooked in distribution models. Here we demonstrate that it is highly important for the persistence of endemic and endangered amphibians found in the threatened and fragile ecosystems that are the rocky plateaus in Western Maharashtra, India. These plateaus are ferricretes of laterite and characterise the northern section of the Western Ghats/Sri Lanka Biodiversity Hotspot, the eighth most important global hotspot and one of the three most threatened by population growth. We present statistically supported habitat associations for endangered and data-deficient Indian amphibians, demonstrating significant relationships between individual species and their microhabitats. Data were collected during early monsoon across two seasons. Twenty-one amphibian taxa were identified from 14 lateritic plateaus between 67 and 1179m above sea level. Twelve of the study taxa had significant associations with microhabitats using a stepwise analysis of the AICc subroutine (distLM, Primer-e, v7). Generalist taxa were associated with increased numbers of microhabitat types. Non-significant associations are reported for the remaining 9 taxa. Microhabitat distribution was spatially structured and driven by climate and human activity. Woody plants were associated with 44% of high-elevation taxa. Of the 8 low-elevation taxa 63% related to water bodies and 60% of those were associated with pools. Rock size and abundance were important for 33% of high elevation specialists. Three of the 4 caecilians were associated with rocks in addition to soil and stream presence. We conclude the plateaus are individualistic patches whose habitat quality is defined by their microhabitats within climatic zones.

The Meladema Laporte, 1835 (Coleoptera, Dytiscidae) of the Sahara Desert

Meladema Laporte, 1835 is a genus of large diving beetles, found in the Western Palaearctic, from the Canary Islands and Madeira to western Turkey (Bilton Ribera 2017). The genus currently contains four species: the widespread M. coriacea Laporte, 1835, distributed from the Canary Islands to Turkey and ranging from southern France and the central Balkans south to the central Sahara, two Atlantic Island endemics, M. imbricata (Wollaston, 1871) from the western Canary Islands and M. lanio (Fabricius, 1775) from the main island of Madeira, and a fourth, recently described species, M. lepidoptera Bilton Ribera, 2017 from the Tyrrhenian Islands (Corsica, Sardinia, Elba, Montecristo) and parts of the Italian mainland (Bilton Ribera 2017).

A new humicolous Parhydraena d'Orchymont, 1937 from South Africa (Coleoptera, Hydraenidae)

Parhydraena d'Orchymont, 1937 currently includes 19 species, 17 of which are endemic to South Africa (Perkins 2009; Bilton 2014). Most species of the genus are fully aquatic, but a few, together with members of other genera of Parhydraenini, occupy moist habitats rich in organic debris (Perkins 2009). These so-called humicolous habitats (Perkins Balfour-Browne 1994) occur both beside water and elsewhere, and have been colonised a number of times by primarily aquatic hydraenid lineages, particularly in Africa and Australasia (e.g. Perkins Balfour-Browne 1994; Perkins 2004a, 2004b; Perkins 2009; Hernando Ribera 2017). Within Parhydraena the toro group (sensu Perkins 2009) comprises four (sub)humicolous species which share a broad habitus, a marked constriction between the pronotum and elytral shoulders, and short legs and maxillary palpi. Whilst phylogenetic relationships within Parhydraena remain unclear in the absence of molecular data, the toro group as currently defined may not be monophyletic, given the differences in aedeagal anatomy observed amongst its members (see Perkins 2009). The most morphologically divergent species described to date is P. toro Perkins, 2009, whose simplified aedeagal anatomy differs considerably from all other known members of the genus. P. toro appears to be narrowly endemic to the inselberg of Table Mountain and surroundings, occurring in damp litter in Afromontane forests and beside seepages and streams (Perkins 2009; DTB pers. obs.). Here I describe a new species from a cool, high-altitude gully in the western end of Hex River Mountains, which closely resembles P. toro in external and aedeagal morphology and shares its humicolous microhabitat.

Physiological niche and geographical range in European diving beetles (Coleoptera: Dytiscidae)

Geographical ranges vary greatly in size and position, even within recent clades, but the factors driving this remain poorly understood. In aquatic beetles, thermal niche has been shown to be related to both the relative range size and position of congeners but whether other physiological parameters play a role is unknown. Metabolic plasticity may be critical for species occupying more variable thermal environments and maintaining this plasticity may trade-off against other physiological processes such as immunocompetence. Here we combine data on thermal physiology with measures of metabolic plasticity and immunocompetence to explore these relationships in Deronectes (Dytiscidae). While variation in latitudinal range extent and position was explained in part by thermal physiology, aspects of metabolic plasticity and immunocompetence also appeared important. Northerly distributed, wide-ranging species apparently used different energy reserves under thermal stress from southern endemic congeners and differed in their antibacterial defences. This is the first indication that these processes may be related to geographical range, and suggests parameters that may be worthy of exploration in other taxa.

A revision of Meladema diving beetles (Coleoptera, Dytiscidae), with the description of a new species from the central Mediterranean based on molecules and morphology

Meladema Laporte, 1835 are relatively large, stream-dwelling diving beetles, distributed widely in the Western Palaearctic, from the Atlantic Islands to Turkey, and from southern France and the Balkans to the central Sahara. In addition to the three previously recognised taxa (M. coriacea Laporte, 1835, M. imbricata (Wollaston, 1871) and M. lanio (Fabricius, 1775)) we describe a new, cryptic, species from the central Mediterranean area, which can be distinguished from M. coriacea on both DNA sequence data and morphology, and provide a key to known species of the genus. Based on the study of genotyped material, both recent and archival, as well as the examination of a large number of museum specimens, we show that M. lepidopterasp. n. occurs to the apparent exclusion of M. coriacea on Corsica, Sardinia and islands of the Tuscan Archipelago, but that both taxa are found in peninsular Italy, where they may occasionally hybridize. In the absence of the original type series, we designate a neotype for M. coriacea, and take the opportunity to designate a lectotype for M. lanio. Morphological variation in Meladema species is discussed, including that seen in known and presumed hybrids. Our study highlights the incomplete state of knowledge of Mediterranean biodiversity, even in relatively large, supposedly well-studied taxa.

The chicken or the egg? Adaptation to desiccation and salinity tolerance in a lineage of water beetles

Transitions from fresh to saline habitats are restricted to a handful of insect lineages, as the colonization of saline waters requires specialized mechanisms to deal with osmotic stress. Previous studies have suggested that tolerance to salinity and desiccation could be mechanistically and evolutionarily linked, but the temporal sequence of these adaptations is not well established for individual lineages. We combined molecular, physiological and ecological data to explore the evolution of desiccation resistance, hyporegulation ability (i.e., the ability to osmoregulate in hyperosmotic media) and habitat transitions in the water beetle genus Enochrus subgenus Lumetus (Hydrophilidae). We tested whether enhanced desiccation resistance evolved before increases in hyporegulation ability or vice versa, or whether the two mechanisms evolved in parallel. The most recent ancestor of Lumetus was inferred to have high desiccation resistance and moderate hyporegulation ability. There were repeated shifts between habitats with differing levels of salinity in the radiation of the group, those to the most saline habitats generally occurring more rapidly than those to less saline ones. Significant and accelerated changes in hyporegulation ability evolved in parallel with smaller and more progressive increases in desiccation resistance across the phylogeny, associated with the colonization of meso- and hypersaline waters during global aridification events. All species with high hyporegulation ability were also desiccation-resistant, but not vice versa. Overall, results are consistent with the hypothesis that desiccation resistance mechanisms evolved first and provided the physiological basis for the development of hyporegulation ability, allowing these insects to colonize and diversify across meso- and hypersaline habitats.

Pleistocene range shifts, refugia and the origin of widespread species in western Palaearctic water beetles

Quaternary glacial cycles drove major shifts in both the extent and location of the geographical ranges of many organisms. During glacial maxima, large areas of central and northern Europe were inhospitable to temperate species, and these areas are generally assumed to have been recolonized during interglacials by range expansions from Mediterranean refugia. An alternative is that this recolonization was from non-Mediterranean refugia, in central Europe or western Asia, but data on the origin of widespread central and north European species remain fragmentary, especially for insects. We studied three widely distributed lineages of freshwater beetles (the Platambus maculatus complex, the Hydraena gracilis complex, and the genus Oreodytes), all restricted to running waters and including both narrowly distributed southern endemics and widespread European species, some with distributions spanning the Palearctic. Our main goal was to determine the role of the Pleistocene glaciations in shaping the diversification and current distribution of these lineages. We sequenced four mitochondrial and two nuclear genes in populations drawn from across the ranges of these taxa, and used Bayesian probabilities and Maximum Likelihood to reconstruct their phylogenetic relationships, age and geographical origin. Our results suggest that all extant species in these groups are of Pleistocene origin. In the H. gracilis complex, the widespread European H. gracilis has experienced a rapid, recent range expansion from northern Anatolia, to occupy almost the whole of Europe. However, in the other two groups widespread central and northern European taxa appear to originate from central Asia, rather than the Mediterranean. These widespread species of eastern origin typically have peripherally isolated forms in the southern Mediterranean peninsulas, which may be remnants of earlier expansion-diversification cycles or result from incipient isolation of populations during the most recent Holocene expansion. The accumulation of narrow endemics of such lineages in the Mediterranean may result from successive cycles of range expansion, with subsequent speciation (and local extinction in glaciated areas) through multiple Pleistocene climatic cycles.

Water beetles from the Bokkeveld Plateau: a semi-arid hotspot of freshwater biodiversity in the Northern Cape of South Africa

The Bokkeveld Plateau in the Northern Cape of South Africa supports a complex transition zone between the fynbos and succulent karoo biomes on the margins of Namaqualand. A combination of regular winter rainfall, geology and strong rainfall gradients mean that the region supports a diverse and highly endemic flora. Recent sampling of aquatic beetles in the Bokkeveld demonstrates that this region also has a diverse freshwater fauna, including a number of apparent endemics. Five new species of Hydraenidae (Pterosthetops chrysomallus sp. nov., Parastetops porcellus sp. nov., Mesoceration castaneum sp. nov., M. chasmum sp. nov., and M. sabulosum sp. nov.) are described from the Bokkeveld, and new records provided for 68 other water beetle taxa recorded during recent fieldwork in the region, 28 of which are new to Northern Cape Province. Most of the newly described species are relatively common in the region, suggesting that additional taxa may remain undetected in this apparent hotspot of freshwater diversity.

A revision of the South African riffle beetle genus <i>Leielmis</i> Delève, 1964 (Coleoptera: Elmidae)

The riffle beetle genus Leielmis Delève, 1964 is redescribed and shown to contain three species, all of which are apparently endemic to the South African Cape, where they live in permanent mountain streams with cold running water. A lectotype is designated for Helmis georyssoides Grouvelle, 1890, and two additional species (L. gibbosus sp. nov. and L. hirsutus sp. nov.) are described for the first time. Following study of the type series, L. georyssoides is shown to be endemic to Table Mountain; most specimens previously assigned to this taxon representing an additional species (L. gibbosus sp. nov.), widespread in the interior Cape Fold Mountains. The record of Leielmis from Angola is considered highly doubtful. Comparative notes and a key are provided to allow the identification of known species of the genus.

Metabolic and reproductive plasticity of core and marginal populations of the eurythermic saline water bug Sigara selecta (Hemiptera: Corixidae) in a climate change context

Ongoing climate change is driving dramatic range shifts in diverse taxa worldwide, and species responses to global change are likely to be determined largely by population responses at geographical range margins. Here we investigate the metabolic and reproductive plasticity in response to water temperature and salinity variation of two populations of the eurythermic saline water bug Sigara selecta: one population located close to the northern edge of its distribution, in a relatively cold, thermally stable region (SE England - 'marginal'), and one close to the range centre, in a warmer and more thermally variable Mediterranean climate (SE Spain - 'core'). We compared metabolic and oviposition rates and egg size, following exposure to one of four different combinations of temperature (15 and 25°C) and salinity (10 and 35gL^-1). Oviposition rate was significantly higher in the marginal population, although eggs laid were smaller overall. No significant differences in oxygen consumption rates were found between core and marginal populations, although the marginal population showed higher levels of plasticity in both metabolic and reproductive traits. Our results suggest that population-specific responses to environmental change are complex and may be mediated by differences in phenotypic plasticity. In S. selecta, the higher plasticity of the marginal population may facilitate both its persistence in current habitats and northward expansion with future climatic warming. The less plastic core population may be able to buffer current environmental variability with minor changes in metabolism and fecundity, but could be prone to extinction if temperature and salinity changes exceed physiological tolerance limits in the future.

Frequent discordance between morphology and mitochondrial DNA in a species group of European water beetles (Coleoptera: Dytiscidae)

The Hydroporus memnonius species group includes both widespread and range restricted diving beetle taxa in the western Palaearctic, some of which have been divided into a number of geographical subspecies. Of these, Hydroporus necopinatus is distributed in the far west of Europe, from central Spain to southern Britain, and has been split into three subspecies, occurring in Iberia (necopinatus sst.), France (robertorum) and England (roni) respectively—the last of these being a rare example of an insect taxon apparently endemic to northern Europe. Here we explore inter-relationships between populations and subspecies of H. necopinatus and related members of the Hydroporus melanarius subgroup, using mitochondrial COI sequence data. We reveal widespread discordance between mitochondrial DNA sequence variation and morphology in areas where H. necopinatus and H. melanarius come into contact, consistent with historical introgressive hybridization between these taxa. In light of this discordance, the lack of clear genetic divergence between H. necopinatus subspecies, and the fact that both robertorum and roni are morphologically intermediate between H. necopinatus sstr. and H. melanarius, we suggest that these taxa may be of hybridogenic origin, rather than representing discrete evolutionary lineages.

Diversity and distribution of polyphagan water beetles (Coleoptera) in the Lake St Lucia system, South Africa

Water beetles belonging to the suborder Polyphaga vary greatly in larval and adult ecologies, and fulfil important functional roles in shallow-water ecosystems by processing plant material, scavenging and through predation. This study investigates the species richness and composition of aquatic polyphagan assemblages in and around the St Lucia estuarine lake (South Africa), within the iSimangaliso Wetland Park, a UNESCO World Heritage Site. A total of 32 sites were sampled over three consecutive collection trips between 2013 and 2015. The sites encompassed a broad range of aquatic habitats, being representative of the variety of freshwater and estuarine environments present on the St Lucia coastal plain. Thirty-seven polyphagan taxa were recorded during the dedicated surveys of this study, in addition to seven species-level records from historical collections. Most beetles recorded are relatively widespread Afrotropical species and only three are endemic to South Africa. Samples were dominated by members of the Hydrophilidae (27 taxa), one of which was new to science (Hydrobiomorphaperissinottoi Bilton, 2016). Despite the fauna being dominated by relatively widespread taxa, five represent new records for South Africa, highlighting the poor state of knowledge on water beetle distribution patterns in the region. Wetlands within the dense woodland characterising the False Bay region of St Lucia supported a distinct assemblage of polyphagan beetles, whilst sites occurring on the Eastern and Western Shores of Lake St Lucia were very similar in their beetle composition. In line with the Afrotropical region as a whole, the aquatic Polyphaga of St Lucia appear to be less diverse than the Hydradephaga, for which 68 species were recorded during the same period. However, the results of the present study, in conjunction with those for Hydradephaga, show that the iSimangaliso Wetland Park contains a high beetle diversity. The ongoing and future ecological protection of not only the estuarine lake itself, but also surrounding freshwater wetlands, is imperative and should be taken into consideration during future management planning for the park.

Aquatic insects dealing with dehydration: do desiccation resistance traits differ in species with contrasting habitat preferences?

Background

Desiccation resistance shapes the distribution of terrestrial insects at multiple spatial scales. However, responses to drying stress have been poorly studied in aquatic groups, despite their potential role in constraining their distribution and diversification, particularly in arid and semi-arid regions.

Methods

We examined desiccation resistance in adults of four congeneric water beetle species (Enochrus, family Hydrophilidae) with contrasting habitat specificity (lentic vs. lotic systems and different salinity optima from fresh- to hypersaline waters). We measured survival, recovery capacity and key traits related to desiccation resistance (fresh mass, % water content, % cuticle content and water loss rate) under controlled exposure to desiccation, and explored their variability within and between species.

Results

Meso- and hypersaline species were more resistant to desiccation than freshwater and hyposaline ones, showing significantly lower water loss rates and higher water content. No clear patterns in desiccation resistance traits were observed between lotic and lentic species. Intraspecifically, water loss rate was positively related to specimens’ initial % water content, but not to fresh mass or % cuticle content, suggesting that the dynamic mechanism controlling water loss is mainly regulated by the amount of body water available.

Discussion

Our results support previous hypotheses suggesting that the evolution of desiccation resistance is associated with the colonization of saline habitats by aquatic beetles. The interespecific patterns observed in Enochrus also suggest that freshwater species may be more vulnerable than saline ones to drought intensification expected under climate change in semi-arid regions such as the Mediterranean Basin.

A new species of Anacaena Thomson, 1859 from South Africa (Coleoptera: Hydrophilidae)

Anacaena namaqua sp. nov. is described from the Northern Cape and Western Cape provinces of South Africa, in an area transitional between the fynbos and succulent karoo biomes. The habitus, aedeagus, femoral pubescence and habitats of the new species are illustrated, together with details of its ecology. A key to all Anacaena confirmed from South Africa to date is also provided.

Predaceous water beetles (Coleoptera, Hydradephaga) of the Lake St Lucia system, South Africa: biodiversity, community ecology and conservation implications

Water beetles are one of the dominant macroinvertebrate groups in inland waters and are excellent ecological indicators, reflecting both the diversity and composition of the wider aquatic community. The predaceous water beetles (Hydradephaga) make up around one-third of known aquatic Coleoptera and, as predators, are a key group in the functioning of many aquatic habitats. Despite being relatively well-known taxonomically, ecological studies of these insects in tropical and subtropical systems remain rare. A dedicated survey of the hydradephagan beetles of the Lake St Lucia wetlands (South Africa) was undertaken between 2013 and 2015, providing the first biodiversity census for this important aquatic group in the iSimangaliso Wetland Park, a UNESCO World Heritage Site within the Maputaland biodiversity hotspot. A total of 32 sites covering the entire spectrum of waterbody types were sampled over the course of three collecting trips. The Lake St Lucia wetlands support at least 68 species of Hydradephaga, a very high level of diversity comparing favourably with other hotspots on the African continent and elsewhere in the world and a number of taxa are reported for South Africa for the first time. This beetle assemblage is dominated by relatively widespread Afrotropical taxa, with few locally endemic species, supporting earlier observations that hotspots of species richness and centres of endemism are not always coincident. Although there was no significant difference in the number of species supported by the various waterbody types sampled, sites with the highest species richness were mostly temporary depression wetlands. This contrasts markedly with the distribution of other taxa in the same system, such as molluscs and dragonflies, which are most diverse in permanent waters. Our study is the first to highlight the importance of temporary depression wetlands and emphasises the need to maintain a variety of wetland habitats for aquatic conservation in this biodiverse region.

Two new water beetles from the South African Cape (Coleoptera, Hydraenidae)

Pterosthetops nitidus sp. nov. and Oomtelecopon namaqum sp. nov. are described from the Western and Northern Cape Provinces of South Africa respectively. Diagnostic notes are provided for each species, together with details of occupied microhabitats.

Observed shifts in the contact zone between two forms of the diving beetle Hydroporus memnonius are consistent with predictions from sexual conflict

Sexual conflict drives both inter- and intrasexual dimorphisms in many diving beetles, where male persistence and female resistance traits co-evolve in an antagonistic manner. To date most studies have focussed on species where rough and smooth females and their associated males typically co-occur within populations, where phenotype matching between morphs may maintain forms as stable polymorphisms. The Palaearctic diving beetle Hydroporus memnonius is characterised by having dimorphic (rough var. castaneus and smooth, shining) females and associated males which differ in persistence traits; the two forms being largely distributed parapatrically. In this species, instead of mating trade-offs between morphs, males associated with castaneus females should have a mating advantage with both this form and shining females, due to their increased persistence abilities on either cuticular surface. This may be expected to lead to the replacement of the shining form with castaneus in areas where the two come into contact. Using data collected over a thirty year period, we show that this process of population replacement is indeed occurring, castaneus having expanded significantly at the expense of the shining female form. Whilst populations of both forms close to the contact zone appear to differ in their thermal physiology, these differences are minor and suggest that the expansion of castaneus is not linked to climatic warming in recent decades. Instead we argue that the observed spread of castaneus and its associated male may result from the dynamics of sexually antagonistic coevolution in this beetle.

Home advantage? Decomposition across the freshwater-estuarine transition zone varies with litter origin and local salinity

Expected increases in the frequency and intensity of storm surges and river flooding may greatly affect the relative salinity of estuarine environments over the coming decades. In this experiment we used detritus from three contrasting environments (marine Fucus vesiculosus; estuarine Spartina anglica; terrestrial Quercus robur) to test the prediction that the decomposition of the different types of litter would be highest in the environment with which they are associated. Patterns of decomposition broadly fitted our prediction: Quercus detritus decomposed more rapidly in freshwater compared with saline conditions while Fucus showed the opposite trend; Spartina showed an intermediate response. Variation in macro-invertebrate assemblages was detected along the salinity gradient but with different patterns between estuaries, suggesting that breakdown rates may be linked in part to local invertebrate assemblages. Nonetheless, our results suggest that perturbation of salinity gradients through climate change could affect the process of litter decomposition and thus alter nutrient cycling in estuarine transition zones. Understanding the vulnerability of estuaries to changes in local abiotic conditions is important given the need to better integrate coastal proceses into a wider management framework at a time when coastlines are increasingly threatened by human activities.

Crenitis bicolor sp. n. from the Kamiesberg of South Africa (Coleoptera: Hydrophilidae)

Crenits Bedel is a small hydrophilid genus of 41 species (Hansen, 1999; Hebauer, 1994, 2005), distributed acrossEurasia,Africa and theAmericas. The genus is particularly diverse in temperate regions, with the eastern Palaearctic and Nearctic regions containing the highest concentrations of taxa. The eight described African species are all restricted to temperateSouth Africa, most being found within the winter rainfall area of theWestern Cape (Hebauer, 1994). Here I describe a distinctive new species on the basis of specimens collected in the high Kamiesberg of Namaqualand in 2010. Specimens were studied using a Leica MZ8 stereomicroscope, with a Fluopac FP1 fluorescent illuminator. The habitus photograph was taken with a Canon EOS 600D camera fitted to a Leica Z6 Apo macroscope, fitted with a 2x objective lens. Specimens were illuminated using two Fluopac FP1 illuminators and a fibre-optic swan-neck illuminator to avoid shadow, light being diffused using a tracing-paper collar placed around the specimen. The aedeagus was traced from an image stack made using a Canon EOS 600D on a Brunel SP100 microscope at x 400 magnification. Image stacks were produced by hand, and combined using Helicon Focus software.

New species and new records of Mesoceration Janssens, 1967 from South Africa (Coleoptera, Hydraenidae)

Mesoceration Janssens, 1967 is the most speciose genus of Prosthetopinae, most of the 44 described species being restricted to South Africa, and almost all occupying the benthic zone of streams and rivers. Here seven species are described as new: Mesoceration caniplenum sp. nov., M. foggoi sp. nov., M. helmei sp. nov., M. hirsutum sp. nov., M. rugulosum sp. nov., M. sewefonteinense sp. nov. and M. sinclairi sp. nov., bringing the number of known species to 51. All seven new species have been discovered during recent, targeted sampling of South African Hydraenidae. New collection records resulting from this fieldwork are also provided for 27 previously described species, together with ecological notes.

A review of the Canthyporus exilis group, with the description of two new species (Coleoptera: Dytiscidae)

Canthyporus namaqualacrimus sp. nov. and Canthyporus pallidus sp. nov. are described from the Namaqualand region of South Africa, both members of the exilis group. A revised key to species of the group is provided, together with details of the external and spermathecal tract morphology of the female of Canthyporus aenigmaticus Biström & Nilsson, 2006, a species previously known only from the male holotype. The opportunity is also taken to present new ecological and distributional data on members of the exilis group, most of which are primarily associated with springs and seepage habitats.

Oxygen-limited thermal tolerance is seen in a plastron-breathing insect and can be induced in a bimodal gas exchanger

Thermal tolerance has been hypothesized to result from a mismatch between oxygen supply and demand. However, the generality of this hypothesis has been challenged by studies on various animal groups, including air-breathing adult insects. Recently, comparisons across taxa have suggested that differences in gas exchange mechanisms could reconcile the discrepancies found in previous studies. Here, we test this suggestion by comparing the behaviour of related insect taxa with different gas exchange mechanisms, with and without access to air. We demonstrate oxygen-limited thermal tolerance in air-breathing adults of the plastron-exchanging water bug Aphelocheirus aestivalis. Ilyocoris cimicoides, a related, bimodal gas exchanger, did not exhibit such oxygen-limited thermal tolerance and relied increasingly on aerial gas exchange with warming. Intriguingly, however, when denied access to air, oxygen-limited thermal tolerance could also be induced in this species. Patterns in oxygen-limited thermal tolerance were found to be consistent across life-history stages in these insects, with nymphs employing the same gas exchange mechanisms as adults. These results advance our understanding of oxygen limitation at high temperatures; differences in the degree of respiratory control appear to modulate the importance of oxygen in setting tolerance limits.

Summary: Oxygen does not appear to universally limit thermal tolerance, but instead, oxygen-limited thermal tolerance is context dependent, being related to a species’ capacity to regulate oxygen consumption.

The comparative osmoregulatory ability of two water beetle genera whose species span the fresh-hypersaline gradient in inland waters (Coleoptera: Dytiscidae, Hydrophilidae)

A better knowledge of the physiological basis of salinity tolerance is essential to understanding the ecology and evolutionary history of organisms that have colonized inland saline waters. Coleoptera are amongst the most diverse macroinvertebrates in inland waters, including saline habitats; however, the osmoregulatory strategies they employ to deal with osmotic stress remain unexplored. Survival and haemolymph osmotic concentration at different salinities were examined in adults of eight aquatic beetle species which inhabit different parts of the fresh-hypersaline gradient. Studied species belong to two unrelated genera which have invaded saline waters independently from freshwater ancestors; Nebrioporus (Dytiscidae) and Enochrus (Hydrophilidae). Their osmoregulatory strategy (osmoconformity or osmoregulation) was identified and osmotic capacity (the osmotic gradient between the animal's haemolymph and the external medium) was compared between species pairs co-habiting similar salinities in nature. We show that osmoregulatory capacity, rather than osmoconformity, has evolved independently in these different lineages. All species hyperegulated their haemolymph osmotic concentration in diluted waters; those living in fresh or low-salinity waters were unable to hyporegulate and survive in hyperosmotic media (> 340 mosmol kg(-1)). In contrast, the species which inhabit the hypo-hypersaline habitats were effective hyporegulators, maintaining their haemolymph osmolality within narrow limits (ca. 300 mosmol kg(-1)) across a wide range of external concentrations. The hypersaline species N. ceresyi and E. jesusarribasi tolerated conductivities up to 140 and 180 mS cm(-1), respectively, and maintained osmotic gradients over 3500 mosmol kg(-1), comparable to those of the most effective insect osmoregulators known to date. Syntopic species of both genera showed similar osmotic capacities and in general, osmotic responses correlated well with upper salinity levels occupied by individual species in nature. Therefore, osmoregulatory capacity may mediate habitat segregation amongst congeners across the salinity gradient.

A new species of Yola Gozis, 1886 from the Western Cape of South Africa (Coleoptera: Dytiscidae: Bidessini)

Yola matsikammae sp. nov. is described from the Matsikammaberg, an inselberg on the northern edge of the fynbos biome of the Western Cape, South Africa. A key is provided to separate the new species from other southern African members of the Yola bicarinata group. Y. matsikammae sp. nov. bears a superficial resemblance to Sharphydrus species, particularly Sharphydrus brincki Bilton, 2013 with which it was found to co-occur. Comparative notes to separate these taxa are also included. 

Two new water beetles from the Hantamsberg, an inselberg in the Northern Cape of South Africa (Coleoptera, Hydraenidae)

Mesoceration hantam sp. nov. and Parhydraena faeni sp. nov., are described from the Hantamsberg plateau, an inselberg in the Northern Cape of South Africa. The new species are so far known only from temporary waters on the Hantamsberg summit, where they were both abundant. Sampling in these mountains also revealed an interesting accompanying water beetle fauna, including the northernmost known record of Hydropeplus montanus Omer-Cooper, a species characteristic of mountain fynbos further south in the region.

Thermal niche evolution and geographical range expansion in a species complex of western Mediterranean diving beetles

BACKGROUND

Species thermal requirements are one of the principal determinants of their ecology and biogeography, although our understanding of the interplay between these factors is limited by the paucity of integrative empirical studies. Here we use empirically collected thermal tolerance data in combination with molecular phylogenetics/phylogeography and ecological niche modelling to study the evolution of a clade of three western Mediterranean diving beetles, the Agabus brunneus complex.

RESULTS

The preferred mitochondrial DNA topology recovered A. ramblae (North Africa, east Iberia and Balearic islands) as paraphyletic, with A. brunneus (widespread in the southwestern Mediterranean) and A. rufulus (Corsica and Sardinia) nested within it, with an estimated origin between 0.60-0.25 Ma. All three species were, however, recovered as monophyletic using nuclear DNA markers. A Bayesian skyline plot suggested demographic expansion in the clade at the onset of the last glacial cycle. The species thermal tolerances differ significantly, with A. brunneus able to tolerate lower temperatures than the other taxa. The climatic niche of the three species also differs, with A. ramblae occupying more arid and seasonal areas, with a higher minimum temperature in the coldest month. The estimated potential distribution for both A. brunneus and A. ramblae was most restricted in the last interglacial, becoming increasingly wider through the last glacial and the Holocene.

CONCLUSIONS

The A. brunneus complex diversified in the late Pleistocene, most likely in south Iberia after colonization from Morocco. Insular forms did not differentiate substantially in morphology or ecology, but A. brunneus evolved a wider tolerance to cold, which appeared to have facilitated its geographic expansion. Both A. brunneus and A. ramblae expanded their ranges during the last glacial, although they have not occupied areas beyond their LGM potential distribution except for isolated populations of A. brunneus in France and England. On the islands and possibly Tunisia secondary contact between A. brunneus and A. ramblae or A. rufulus has resulted in introgression. Our work highlights the complex dynamics of speciation and range expansions within southern areas during the last glacial cycle, and points to the often neglected role of North Africa as a source of European biodiversity.

New species and new records of Pterosthetops: eumadicolous water beetles of the South African Cape (Coleoptera, Hydraenidae)

Pterosthetops is one of a number of hydraenid genera endemic to the Cape of South Africa, whose minute moss beetle fauna is amongst the most diverse on earth. Here seven species are described as new: Pterosthetops baini sp. nov., Pterosthetops coriaceus sp. nov., Pterosthetops indwei sp. nov., Ptersothetops pulcherrimus sp. nov., Pterosthetops swartbergensis sp. nov., Pterosthetops tuberculatus sp. nov. and Pterosthetops uitkyki sp. nov., all from mountains in the Western Cape region. New collection records are also provided for all five previously described members of the genus, together with a revised key. Pterosthetops appear to be specialist inhabitants of seepages over rock faces (hygropetric/madicolous habitats), rarely being found outside such situations.

A taxonomic revision of South African Sharphydrus, with the description of two new species (Coleoptera: Dytiscidae: Bidessini)

Sharphydrus Omer-Cooper, 1958 is one of two endemic bidessine genera currently recognised from South Africa. Here Sharphydrus brincki sp. nov. and Sharphydrus kamiesbergensis sp. nov. are described from the Cederberg and Gydopas areas of the Western Cape, and the high Kamiesberg of the Northern Cape respectively, doubling the known species of this genus. It is shown that S. brincki sp. nov. has been included under S. capensis (Omer-Cooper, 1955) in the past, but that these are quite distinct taxa, differing in the extent of their elytral keels and male genitalia. Sharphydrus species are inhabitants of pools in seasonally fluctuating rivers, the new species described here occurring in areas which are somewhat transitional between fynbos and karoo biomes. An updated key is presented to Sharphydrus species, together with data on the distribution and ecology of known species, and a discussion of the status of the genus within the Bidessini.