Smelling in the dark: Phylogenomic insights into the chemosensory system of a subterranean beetle.

The chemosensory system has experienced relevant changes in subterranean animals, facilitating the perception of specific chemical signals critical to survival in their particular environment. However, the genomic basis of chemoreception in cave-dwelling fauna has been largely unexplored. We generated de novo transcriptomes for antennae and body samples of the troglobitic beetle Speonomus longicornis (whose characters suggest an extreme adaptation to a deep subterranean environment) in order to investigate the evolutionary origin and diversification of the chemosensory gene repertoire across coleopterans through a phylogenomic approach. Our results suggested a diminished diversity of odourant and gustatory gene repertoires compared to polyphagous beetles that inhabit surface habitats. Moreover, S. longicornis showed a large diversity of odourant-binding proteins, suggesting an important role of these proteins in capturing airborne chemical cues. We identified a gene duplication of the ionotropic coreceptor IR25a, a highly conserved single-copy gene in protostomes involved in thermal and humidity sensing. In addition, no homologous genes to sugar receptors or the ionotropic receptor IR41a were detected. Our findings suggest that the chemosensory gene repertoire of this cave beetle may result from adaptation to the highly specific ecological niche it occupies, and that gene duplication and loss may have played an important role in the evolution of gene families involved in chemoreception. Altogether, our results shed light on the genomic basis of chemoreception in a cave-dwelling invertebrate and pave the road towards understanding the genomic underpinnings of adaptation to the subterranean lifestyle at a deeper level.

Geographic variation in acclimation responses of thermal tolerance in South African diving beetles (Dytiscidae: Coleoptera).

Understanding sources of variation in animal thermal limits is critical to forecasting ecological responses to climate change. Here, we estimated upper and lower thermal limits, and their capacity to respond to thermal acclimation, in several species and populations of diving beetles (Dytiscidae) from diverse geographic regions representative of variable climate within South Africa. We also considered ecoregions and latitudinal ranges as potential predictors of thermal limits and the plasticity thereof. For upper thermal limits, species showed significant variation and limited acclimation-related plasticity. Lower thermal limits responded to acclimation in some cases and showed marked variation among species that could be explained by taxonomic affiliation and ecoregion. Limited acclimation ability in the species included in this study suggest plasticity of thermal limits will not be a likely buffer for coping with climate change. From the present results for the Dytiscidae of the region, it appears the group may be particularly susceptible to heat and/or drought and may thus serve as useful indicator species of ecosystem change. Understanding how these climate-related impacts play out at different spatial and temporal scales will have profound implications for conservation management and functional responses, especially important in a region already showing a trend for warming and drying.

A redefinition of the genus Troglocharinus Reitter, 1908, with description of new species (Coleoptera, Leiodidae, Cholevinae, Leptodirini).

We redefine the genus Troglocharinus Reitter, 1908 based on a phylogenetic analysis with a combination of mitochondrial and molecular data. We recovered the current Speonomites mengeli (Jeannel, 1910) and S. mercedesi (Zariquiey, 1922) as valid, separate species within the Troglocharinus clade, not directly related to Speonomites Jeannel, 1910, a finding corroborated by a detailed study of the male and female genitalia. In consequence, we reinstate Speonomus mercedesi Zariquiey, 1922 stat. nov. as a valid species, transfer both of them to the genus Troglocharinus, T. mengeli (Jeannel, 1910) comb. nov. and T. mercedesi (Zariquiey, 1922) comb. nov., and redescribe the genus. The study of new material from the distribution area of the former S. mengeli revealed the presence of two undescribed species, T. sendrai sp. nov. and T. fadriquei sp. nov., which we describe herein. We designate the lectotype of Speonomus vinyasi Escolà, 1971 to fix its identity, as among its syntypes there are two different species. In agreement with the results of the phylogenetic analyses we establish the synonymy between the genus Speonomites and Pallaresiella Fresneda, 1998 syn. nv.

Habitat preference and diversification rates in a speciose lineage of diving beetles.

The long-term geological stability of aquatic habitats has been demonstrated to be a determinant in the evolution of macroinvertebrate fauna, with species in running (lotic) waters having lower dispersal abilities, smaller ranges and higher gene flow between populations than species in standing (lentic) environments. Lotic species have been hypothesized to be more specialised, but the diversification dynamics of both habitat types have not been studied in detail. Using a speciose lineage of water beetles we test here whether diversification rates are related to the habitat preference of the species and its consequences on turnover, which we expect to be higher for lotic taxa. Moreover, we tested whether life in lotic environments is acting as an evolutionary dead-end as it is considered an ecological specialisation. We built a comprehensive molecular phylogeny with 473 terminals representing 421 of the 689 known species of the tribe Hydroporini (Coleoptera, Dytiscidae), using a combination of sequences from four mitochondrial and two nuclear genes plus 69 mitogenomes obtained with NGS. We found a general pattern of gradual acceleration of diversification rate with time, with 2-3 significant diversification shifts. However, habitat is not the main factor driving diversification in Hydroporini based on SecSSE analyses. The most recent common ancestor of Hydroporini was reconstructed as a lotic species, with multiple shifts to lentic environments. Most frequent transitions were estimated from lentic and lotic habitats to the category "both", followed by transitions from lotic to lentic and lentic to lotic respectively, although with very similar rates. Contrary to expectations, we found little evidence for differences in diversification dynamics between habitats, with lotic environments clearly not acting as evolutionary dead-ends in Hydroporini.

Three new species and DNA sequence data of the rare South American water beetle genus Adelphydraena Perkins, 1989 (Coleoptera: Hydraenidae).

Three new species of the very rarely collected water beetle genus Adelphydraena Perkins, 1989 are described from Brazil, Guyana, and Suriname. Illustrations of the male genitalia of the two previously known species in the genus, A. orchymonti Perkins and A. spangleri Perkins from Venezuela, are presented for the first time. High resolution digital images of the habitus of all species are given, and geographical distributions mapped. New species described are Adelphydraena amazonica n. sp. (Brazil), A. spinosa n. sp. (Guyana), and A. surinamensis n. sp. (Suriname). Mitochondrial and nuclear DNA sequence data is given for three of the five species currently known (A. orchymonti, A. spangleri, and A. amazonica). The monophyly of the genus Adelphydraena was strongly supported, but relationships between the sequenced species remain uncertain.

Irreversible habitat specialization does not constrain diversification in hypersaline water beetles.

Specialization to extreme environments is often considered an evolutionary dead-end, leading to irreversible adaptations and reduced evolvability. There is, however, mixed evidence for this macroevolutionary pattern, and limited data from speciose lineages. Here, we tested the effect of habitat specialization to hypersaline waters in the diversification rates of aquatic beetles of the genus Ochthebius (Coleoptera, Hydraenidae), using a molecular phylogeny with more than 50% of the 546 recognized species, including representatives of all but one of the nine recognized subgenera and 17 species groups. Phylogenies were built combining mitochondrial and nuclear genes, with the addition of 42 mitochondrial genomes. Using Bayesian methods of character reconstruction, we show that hypersaline tolerance is an irreversible ecological specialization that arose multiple times. Two lineages of Ochthebius experienced a significant increase in diversification rates, one of them inhabiting hypersaline waters, but there was no overall correlation with habitat or any significant decrease in diversification rates despite the irreversibility of hypersaline tolerance. Our study tested for the first time the impact of hypersaline habitat specialization on diversification rates, finding no support for it to be an evolutionary dead-end. On the contrary, multiple and ancient lineages fully adapted to these extreme osmotic conditions have persisted and diversified over a long evolutionary timescale.

The thoracic morphology of the troglobiontic cholevine species Troglocharinus ferreri (Coleoptera, Leiodidae).

The thoracic morphology of the troglobiontic leiodid species Troglocharinus ferreri (Cholevinae, Leptodirini) is described and documented in detail. The features are mainly discussed with respect to modifications linked with subterranean habits. Troglocharinus is assigned to the moderately modified pholeuonoid morphotype. The body is elongated and slender compared to epigean leiodids and also cave-dwelling species of Ptomaphagini. The legs are elongated, especially the hindlegs, though to a lesser degree than in the most advanced troglobiontic species. The prothorax is moderately elongated but otherwise largely unmodified. Its muscular system is strongly developed, with more muscle bundles that in free-living staphylinoid or hydrophiloid species. The pterothorax is greatly modified, especially the metathoracic flight apparatus. The meso- and metathoracic elements of the elytral locking device are well-developed, whereas the other notal parts are largely reduced. The mesonotum is simplified, with the triangular scutellar shield as the only distinctly developed part. The mesothoracic musculature is strongly reduced, with only 6 muscles compared to 12 or 13 in free-living staphylinoid or hydrophiloid species. The metanotum is greatly reduced, without a recognizable subdivision into prescutum scutum and scutellum. It is strongly narrowing laterally and lacks notal wing processes and other wing-related elements, but well-developed alacristae are present. The wings are reduced to small membranous flap-like structures inserted at the posterior end of the metanotum. A metapostnotum is not developed. Like in the case of the head, cave dwelling species of the related Ptomaphagini and Leptodirini show different trends of adaptations, with a compact ovoid or navicular body shape in the former, and a distinct trend towards elongation of the body and appendages in the latter tribe. Structural affinities of the thoraces of T. ferreri and the troglobiontic trechine carabid Sinaphaenops wangorum are mainly due to the reduced flight apparatus. The degree of muscle reduction in the pterothorax is very similar in both species.

The cephalic morphology of the troglobiontic cholevine species Troglocharinus ferreri (Coleoptera, Leiodidae).

Leiodidae are the second largest subterranean radiation of beetles at family rank. To explore morphological trends linked with troglobiontic habits and characters with potential phylogenetic significance, the head of the cave-dwelling species Troglocharinus ferreri (Cholevinae, Leptodirini) was examined in detail. Overall, the general pattern is similar to what is found in Catops ventricosus (Cholevini). Shared apomorphic features include a fully exposed anterolateral concavity containing the antennal socket, a distinct bead above this depression, a bilobed lip-like structure anterad the labrum, a flat elevated portion of the ventral mandibular surface, and a ventral process at the proximomesal edge of this mandibular area. The tentorial structures are well-developed as in C. ventricosus, with a large laminatentorium and somewhat shortened dorsal arms. The mouthparts are largely unmodified, with the exception of unusually well-developed extrinsic maxillary muscles. Features of T. ferreri obviously linked with subterranean habits are the complete lack of compound eyes, circumocular ridges, and optic lobes. A series of characters is similar to conditions found in other genera of Leptodirini: the head capsule completely lacks a protruding ocular region, a distinct neck is missing, the transverse occipital crest is indistinct, and the antennae are elongate and lack a distinct club. Two different trends of cephalic transformations occur in troglobiontic Leptodirini, with some genera like Troglocharinus and Leptodirus having elongated head capsules and antennae, and others having broadened, more transverse heads. In contrast, the modifications are more uniform in the closely related Ptomaphagini, with a pattern distinctly differing from Leptodirini: the head is transverse, with a distinctly protruding ocular region, a distinct transverse occipital crest, and a very narrow neck region.

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 molecular phylogeny of Speonemadus Jeannel, 1922 with description of two new species from Morocco (Coleoptera: Leiodidae: Cholevinae: Anemadini).

The genus Speonemadus Jeannel, 1922 currently includes 12 species distributed in the Western Mediterranean (Iberian Peninsula, North Africa, Sicily and continental Italy). Two new species are described from Morocco, S. brusteli sp. n. from the Rif and S. comasi sp. n. from the High Atlas, the first in the S. vandalitiae-group of species and the second with an isolated position within the genus. Two species are also resurrected from synonymy, S. pulchellus (Reitter, 1885) stat. rest. (former synonym of S. orchesioides (Fairmaire, 1879)) and S. gracilis (Kraatz, 1870) stat. rest. (former synonym of S. vandalitiae (Heyden, 1870)), raising the total number of species of the genus to 16. Lectotypes are designated for Anemadus pulchellus Reitter, 1885, and Anemadus tenuipes Peyerimhoff, 1917. A molecular phylogeny of the genus Speonemadus is presented, based on a combination of mitochondrial and nuclear genes and including seven of the currently recognised species, one of the newly described (S. brusteli sp. n.) and the two reinstated taxa. The genus is estimated to have diversified from the late Miocene (Tortonian), with successive cladogenetic events related to the isolation of landmasses between Iberia and North Africa, including the opening of the Strait of Gibraltar at the end of the Messinian. The distribution of some of the species of Speonemadus remains still uncertain, due to their frequent misidentification and the problems with their taxonomic status.

The first stygobiont species of Coleoptera from Portugal, with a molecular phylogeny of the Siettitia group of genera (Dytiscidae, Hydroporinae, Hydroporini, Siettitiina).

Iberoporuspluto sp. n., the first stygobiont beetle from Portugal (Dytiscidae, Hydroporinae), is described from a single female from the cave Soprador do Carvalho (Coimbra). The species is highly troglomorphic, depigmented, blind, and with elongated appendages not adapted for swimming. A molecular phylogeny based on a combination of three mitochondrial and two nuclear genes showed the new species to be sister to I.cermenius Castro & Delgado, 2001 from Córdoba (south of Spain), within the subtribe Siettitiina of the tribe Hydroporini. Both species are included in a clade with Siettitiaavenionensis Guignot, 1925 (south of France) and Rhithrodytesagnus Foster, 1992 and R.argaensis Fery & Bilton, 1996 (north of Portugal), in turn sister to the rest of species of genus Rhithrodytes Bameul, 1989, in what is here considered the Siettitia group of genera. We resolve the paraphyly of Rhithrodytes by transferring the two Portuguese species to Iberoporus Castro & Delgado, 2001, I.agnus (Foster, 1992), comb. n. and I.argaensis (Fery & Bilton, 1996), comb. n.

Brachemys (Atelestodes) minotaurus sp.n., a new coastal Malachiidae (Coleoptera) from Crete.

A new species of the costal genus Brachemys Abeille de Perrin, 1890 is described from Crete, B. minotaurus n.sp. (Coleoptera, Malachiidae). The species is included in the subgenus Atelestodes Abeille de Perrin, 1890 due to the lack of modified protarsi, although the subgeneric classification of Brachemys may need to be revised. Specimens of the new species were found running on bare rock in the supralittoral zone, bearing a striking resemblance to ants.

Heat tolerance and acclimation capacity in subterranean arthropods living under common and stable thermal conditions.

Cave-dwelling ectotherms, which have evolved for millions of years under stable thermal conditions, could be expected to have adjusted their physiological limits to the narrow range of temperatures they experience and to be highly vulnerable to global warming. However, most of the few existing studies on thermal tolerance in subterranean invertebrates highlight that despite the fact that they show lower heat tolerance than most surface-dwelling species, their upper thermal limits are generally not adjusted to ambient temperature. The question remains to what extent this pattern is common across subterranean invertebrates. We studied basal heat tolerance and its plasticity in four species of distant arthropod groups (Coleoptera, Diplopoda, and Collembola) with different evolutionary histories but under similar selection pressures, as they have been exposed to the same constant environmental conditions for a long time. Adults were exposed at different temperatures for 1 week to determine upper lethal temperatures. Then, individuals from previous sublethal treatments were transferred to a higher temperature to determine acclimation capacity. Upper lethal temperatures of three of the studied species were similar to those reported for other subterranean species (between 20 and 25°C) and widely exceeded the cave temperature (13-14°C). The diplopod species showed the highest long-term heat tolerance detected so far for a troglobiont (i.e., obligate subterranean) species (median lethal temperature after 7 days exposure: 28°C) and a positive acclimation response. Our results agree with previous studies showing that heat tolerance in subterranean species is not determined by environmental conditions. Thus, subterranean species, even those living under similar climatic conditions, might be differently affected by global warming.

Morphology-based phylogenetic reconstruction of Cholevinae (Coleoptera: Leiodidae): a new view on higher-level relationships.

The current state of knowledge of the suprageneric relationships in Cholevinae is either derived from informal evaluations of putative synapomorphies or based on molecular studies with limited taxonomic sampling. Here we assessed the higher-level relationships in this subfamily based on a phylogenetic analysis of 97 morphological characters scored for 93 terminals, representing all tribes. Both parsimony and Bayesian analyses were used. The monophyletic origin of Cholevinae was corroborated, except for the unexpected inclusion of Leptinus in the implied weighting analysis. Eucatopini + Oritocatopini were retrieved as basal branches in the evolution of Cholevinae. The monophyletic origin of all remaining Cholevinae was confirmed, which is consistent with molecular evidence. Anemadini was non-monophyletic, in accordance with earlier hypotheses. Cholevini was rendered non-monophyletic by the uncertain inclusion of Prionochaeta and the consistent exclusion of Cholevinus. A close affinity of Ptomaphagini to Sciaphyini and Leptodirini was suggested, although the position of Sciaphyes remains uncertain. The phylogenetic hypothesis of Cholevinae provided here is the most comprehensive presently available. The list of characters shows that a substantial part of the data was obtained from the ventral side. This is a strong argument for a detailed pictorial documentation of the ventral body parts in taxonomic descriptions, in contrast to the common practice of only illustrating the dorsal habitus of the beetles.

Report of Frank Balfour-Browne's collecting in Gran Canaria and Madeira (1932-1933), with the description of Ochthebius (Cobalius) lanthanus sp. nov. (Coleoptera, Hydraenidae).

Ochthebius (Cobalius) lanthanus sp. nov. is described from rockpools in Gran Canaria, based on specimens collected by Professor F. Balfour-Browne in 1932 and newly collected material. The species is morphologically very similar to O. (Cobalius) algicola Wollaston, 1871 from Madeira, but at a genetic distance of ca 10% as measured with the gene cytochrome c oxidase subunit 1. The water beetle collections of Balfour-Browne's trip to Gran Canaria (1932) and Madeira (1933) are also reported.

Phylogeny and taxonomic revision of Deronectina Galewski, 1994 (Coleoptera: Dytiscidae: Hydroporinae: Hydroporini).

The subtribe Deronectina Galewski, 1994 (Dytiscidae, Hydroporinae, Hydroporini) is distributed in the Nearctic, in the north of the Neotropical region, and in the Palaearctic and Afrotropical regions. It is currently composed of 194 species and 13 subspecies in eight genera: Amurodytes Fery Petrov, 2013, Boreonectes Angus, 2010, Deronectes Sharp, 1882, Nebrioporus Régimbart, 1906, Oreodytes Seidlitz, 1887, Scarodytes Gozis, 1914, Stictotarsus Zimmermann, 1919, and Trichonectes Guignot, 1941. We present a morphological and a molecular phylogeny of the species of the subtribe, and a revision of their taxonomy to accommodate our phylogenetic results. The morphological phylogeny is based on the study of 54 characters of the adults of 189 species and 2 subspecies, of which 114 species and the 2 subspecies were coded in the morphological matrix. For the molecular phylogeny we investigated 115 species and 11 subspecies, using a combination of fragments of four mitochondrial (COI, 16S rRNA, tRNA-Leu and NAD1) and two nuclear genes (18S rRNA and H3), analysed with maximum likelihood and Bayesian methods. For both datasets we included the type species of all genus-group taxa. The morphological, molecular and combined phylogenies mostly agree with the current classification of the group, but in some cases our results are in contradiction with established genera. Most remarkable are the polyphyly of Stictotarsus and Nebrioporus, the low support for the monophyly and internal phylogeny of Oreodytes, and the low support for the monophyly of Deronectina with molecular data. Thus, we introduce some taxonomic changes in the current classification to accommodate the generic concepts to our phylogenetic results. Nine new genera are established: Clarkhydrus n. gen. (type species Hydroporus roffii Clark, 1862), Hornectes n. gen. (type species Hydroporus quadrimaculatus Horn, 1883), Iberonectes n. gen. (type species Deronectes bertrandi Legros, 1956), Larsonectes n. gen. (type species Potamonectes minipi Larson, 1991), Leconectes n. gen. (type species Hydroporus striatellus LeConte, 1852), Mystonectes n. gen. (type species Deronectes neomexicanus Zimmerman Smith, 1975), Nectoboreus n. gen. (type species Hydroporus aequinoctialis Clark, 1862), Nectomimus n. gen. (type species Oreodytes okulovi Lafer, 1988), and Zaitzevhydrus n. gen. (type species Hydroporus formaster Zaitzev, 1908). Three genera are reinstated as valid: Deuteronectes Guignot, 1945 (stat. rest.) (type species Hydroporus picturatus Horn, 1883), Nectoporus Guignot, 1950 (stat. rest.) (type species Hydroporus abbreviatus Fall, 1923), and Neonectes J. Balfour-Browne, 1940 (stat. rest.) (type species Hydroporus natrix Sharp, 1884). Thirty-six new combinations for species and subspecies thus far treated in the genera Boreonectes, Nebrioporus, Oreodytes and Stictotarsus result from the new classification: Clarkhydrus corvinus (Sharp, 1887) n. comb., C. decemsignatus (Clark, 1862) n. comb., C. deceptus (Fall, 1932) n. comb., C. eximius (Motschulsky, 1859) n. comb., C. falli (Nilsson, 2001) n. comb., C. interjectus (Sharp, 1882) n. comb., C. minax (Zimmerman, 1982) n. comb., C. opaculus (Sharp, 1882) n. comb., C. roffii (Clark, 1862) n. comb., C. spectabilis (Zimmerman, 1982) n. comb., Deuteronectes angustior (Hatch, 1928) n. comb., Hornectes quadrimaculatus (Horn, 1883) n. comb., Iberonectes bertrandi (Legros, 1956) n. comb., Larsonectes minipi (Larson, 1991) n. comb., Leconectes striatellus (LeConte, 1852) n. comb., Mystonectes coelamboides (Fall, 1923) n. comb., M. grammicus (Sharp, 1887) n. comb., M. neomexicanus (Zimmerman Smith, 1975) n. comb., M. panaminti (Fall, 1923) n. comb., M. titulus (Leech, 1945) n. comb., Nectoboreus aequinoctialis (Clark, 1862) n. comb., N. dolerosus (Leech, 1945) n. comb., N. funereus (Crotch, 1873) n. comb., Nectomimus okulovi (Lafer, 1988) n. comb., Nectoporus angelinii (Fery, 2015) n. comb., N. congruus (LeConte, 1878) n. comb., N. crassulus (Fall, 1923) n. comb., N. obesus obesus (LeConte, 1866) n. comb., N. obesus cordillerensis (Larson, 1990) n. comb., N. rhyacophilus (Zimmerman, 1985) n. comb., N. sanmarkii sanmarkii (C.R. Sahlberg, 1826) n. comb., N. sanmarkii alienus (Sharp, 1873) n. comb., N. sierrae (Zimmerman, 1985) n. comb., N. subrotundus (Fall, 1923) n. comb., Zaitzevhydrus formaster formaster (Zaitzev, 1908) n. comb., and Z. formaster ulanulana (C.-K. Yang, 1996) n. comb.

The thoracic morphology of cave-dwelling and free-living ground beetles from China (Coleoptera, Carabidae, Trechinae).

External and internal thoracic structures of two carabid species (Trechini) were examined and documented with different techniques. The study has a main focus on the eyeless cave-dwelling specialist Sinaphaenops wangorum, but detailed information is also provided for a species occurring in cave entrances. The phylogenetic background of the structural features of the thoracic skeletomuscular system was addressed. The thoracic morphology of the examined species was compared to conditions observed in previously studied carabids and non-related subterranean leiodids (Staphylinoidea) in order to identify cave adaptations. Main thoracic character complexes linked with cavernicolous habits in Trechini are elongation of the pro- and mesothorax and the legs, and a complete and irreversible reduction of the flight apparatus. The lost flight capacity is linked with a far reaching modification of skeletal elements of the metathorax including a strongly shortened and simplified metanotum, a shortened metaventrite, and completely reduced wings and sclerites of the wing base. The elongate prothorax together with the long and slender head and elongated legs distinctly increases the activity range in the subterranean lightless environment, which likely facilitates foraging of the carnivorous beetles. Some of the observed features like wing loss and elongation of the anterior thorax and legs are also found in some cave-dwelling Leiodidae (Leptodirini), whereas some other subterranean members of the staphylinoid family have a compact body and legs of normal length. In contrast to the predaceous Trechini, Leptodirini are scavengers.

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 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.

Further studies on Boreonectes Angus, 2010, with a molecular phylogeny of the Palaearctic species of the genus.

Karyotypes are given for Boreonectes emmerichi (Falkenström, 1936) from its type locality at Kangding, China, and for B. alpestris (Dutton & Angus, 2007) from the St Gotthard and San Bernardino passes in the Swiss Alps. A phylogeny based on sequence data from a combination of mitochondrial and nuclear genes recovered western Palaearctic species of Boreonectes as monophyletic with strong support. Boreonectes emmerichi was placed as sister to the north American forms of B. griseostriatus (De Geer, 1774), although with low support. The diversity of Palaearctic species of the B. griseostriatus species group is discussed.