Transoceanic Stepping–stones between Cretaceous waterfalls? The enigmatic biogeography of pantropical Oocyclus cascade beetles

DNA but not always morphology help to recognise monophyletic genera within 'Cercyon' terrestrial water scavenger beetles: a case study of Asiacyon gen. nov. (Coleoptera: Hydrophilidae)

DNA-based studies have revealed that the terrestrial water scavenger beetle genus Cercyon Leach, 1817 (Coleoptera: Hydrophilidae: Sphaeridiinae: Megasternini) is polyphyletic, grouping similarly looking but unrelated species that were not assigned to other genera due to the absence of unusual morphological characters. In this study, we analyse the morphology, DNA data and species diversity of one of the Asian clades of 'Cercyon ' to test whether a natural, phylogeny-based generic classification can be established. We add DNA data (five nuclear and three mitochondrial fragments) for additional species and specimens of the clade to test its monophyly and reveal phylogenetic relationships among species. We perform a detailed morphological study of all species, including SEM micrographs, to reveal synapomorphies of the DNA-based clades. We demonstrate that the lineage, described here as Asiacyon Mai, Jia, Ryndevich & Fikáček, gen. nov., is strongly supported by DNA data, has limited distribution (eastern Asia), and its species share similar biology (inhabiting fresh or decaying plant tissues), though it can be only diagnosed by a combination of plesiomorphic characters. A detailed treatment is provided for the Chinese species, including species diagnoses, illustrations of habitus and male genitalia, (re)descriptions and a key to species. A total of 14 Chinese species are recognised, of which 11 are described as new: Asiacyon pax sp. nov. (Guangdong, Hong Kong, Hunan), A. pseudincretus sp. nov. (Anhui, Jiangxi, Taiwan, Zhejiang), A. vicincretus sp. nov. (Guangdong, Guangxi), A. zhengyucheni sp. nov. (Yunnan), A. huilanae sp. nov. (Yunnan), A. cornipenis sp. nov. (Yunnan), A. belousovi sp. nov. (Yunnan), A. liangchengi sp. nov. (Yunnan), A. paraequalis sp. nov. (Yunnan), A. pengzhongi sp. nov. (Hunan) and A. xiuzhenae sp. nov. (Hainan, Yunnan). Three Chinese species previously classified in Cercyon are transferred to Asiacyon : A. incretus (d'Orchymont, 1941), comb. nov., A. primoricus (Ryndevich & Prokin, 2017), comb. nov. (newly recorded from China) and A. indicus (d'Orchymont, 1926), comb. nov. (newly recorded from China and Laos). Additionally, seven Asian species previously classified in Cercyon are transferred to Asiacyon based on their external morphology, but not studied in detail: A. aequalis (Sharp, 1884), comb. nov., A. conjiciens (Walker, 1858), comb. nov., A. dilutus (Régimbart, 1903), comb. nov., A. placidus (Sharp, 1884), comb. nov., A. pseudodilutus (Satô, 1979), comb. nov., A. retius (Ryndevich & Prokin, 2017), comb. nov., and A. rubicundus (Sharp, 1884), comb. nov. In total, the genus now comprises 21 named species and several undescribed species from India, Myanmar and Indonesia. ZooBank: urn:lsid:zoobank.org:pub:E3C949A0-34E4-46EF-BA6A-2CD048D583B2.

Three new species of Oocyclus Sharp, 1882, with additional records from China (Coleoptera, Hydrophilidae, Laccobiini)

Three new species of the water scavenger beetle genus Oocyclus Sharp, 1882 from China (Oocyclusextensus sp. nov., from Xizang, O.latiorificialis sp. nov. and O.ximaensis sp. nov. from Yunnan) are described and illustrated in detail. Additional faunistic data, illustrations of habitus and male genitalia, and a key to Chinese species are provided.

A review of the Oocyclus Sharp of Ecuador with description of 12 new species (Coleoptera: Hydrophilidae: Laccobiini)

The species of the hygropetric water scavenger beetle genus Oocyclus Sharp, 1882 are reviewed for Ecuador. The genus has not previously been reported from the country. Twelve new species are described: O. ancho sp. n., O. ankas sp. n., O. bellus sp. n., O. kichwa sp. n., O. lepidus sp. n., O. packha sp. n., O. radiatus sp. n., O. rupestris sp. n., O. sumak sp. n., O. ustulatus sp. n., O. yantzaza sp. n., and O. zamora sp. n. One previously described species is newly reported for Ecuador: O. sharpi Short & Perkins 2004. There is at least one additional species that is part of a species complex that includes O. morgani García-Hernández, 2009 from Colombia and O. trujillo Short & García, 2010 from Venezuela. One new synonymy is proposed: the Venezuelan species O. zulianus Short & García, 2010 syn. n. is placed as a junior subjective synonym of O. sharpi Short & Perkins, 2004. A key to all described species known from the Andes region of South America is provided.

Unraveling the evolutionary history of the snakefly family Inocelliidae (Insecta: Raphidioptera) through integrative phylogenetics

Inocelliidae is one of the two extant families of the holometabolan order Raphidioptera (snakeflies), with the modern fauna represented by seven genera and 44 species. The evolutionary history of the family is little-known. Here we present the first phylogenetic and biogeographical analyses based on a worldwide sampling of taxa and datasets combined with morphological characters and mitochondrial genomes, aiming to investigate the intergeneric phylogeny and historical biogeography of Inocelliidae. The phylogenetic inference from the combined analysis of morphological and molecular data recovered the sister-group relationship between a clade of (Negha + Indianoinocellia) + Sininocellia and a clade of Fibla + the Inocellia clade (interiorly nested by Amurinocellia and Parainocellia). Amurinocellia stat.r. and Parainocellia stat.r. et emend.n. are relegated to subgeneric status within Inocellia, whereas a newly erected subgenus of Inocellia, Epinocellia subgen.n., accommodates the former Parainocellia burmana (U. Aspöck and H. Aspöck, 1968) plus a new species Inocellia (Epinocellia) weii sp.n. Further, the Inocellia crassicornis group constitutes the nominotypical subgenus Inocellia stat.n., but the Inocellia fulvostigmata group is paraphyletic. Diversification within Inocelliidae is distinguished by an Eocene divergence leading to extant genera and a Miocene radiation of species. A biogeographical scenario depicts how the diverse inocelliid fauna from East Asia could have originated from western North America via dispersal across the Beringia during the early Tertiary, and how the Miocene ancestors of Inocellia could have accomplished long-distance dispersals via the Tibet-Himalayan corridor or eastern Palaearctic to western Palaearctic. Our results shed new light specifically on the evolution of Inocelliidae and, in general, the Raphidioptera.

Ancient relicts or recent immigrants? Different dating strategies alter diversification scenarios of New Zealand aquatic beetles (Coleoptera: Hydrophilidae: Berosus)

Dated species-level phylogenies are crucial for understanding the origin and evolutionary history of modern faunas, yet difficult to obtain due to the frequent absence of suitable age calibrations at species level. Substitution rates of related or more inclusive clades are often used to overcome this limitation but the accuracy of this approach remains untested. We compared tree dating based on substitution rates with analyses implementing fossil data by direct node-dating and indirect root-age constraints for the New Zealand endemic Berosus water beetles (Coleoptera: Hydrophilidae). The analysis based solely on substitution rates indicated a Miocene colonization of New Zealand and Pleistocene origin of species. By contrast, all analyses that implemented fossil data resulted in significantly older age estimates, indicating an ancient early Cenozoic origin of the New Zealand clade, diversification of species during or after the Oligocene transgression and Miocene-Pliocene origin of within-species population structure. Rate-calibrated time trees were incongruent with recently published Coleoptera time trees, the fossil record of Berosus and the distribution of outgroup species. Strong variation of substitution rates among Coleoptera lineages, as well as among lineages within the family Hydrophilidae, was identified as the principal reason for low accuracy of rate-calibrated analyses, resulting in underestimated node ages in Berosus. We provide evidence that Oligocene to Pliocene events, rather than the Pleistocene Glacial cycles, played an essential role in the formation of the modern New Zealand insect fauna.

Larval chaetotaxy and morphology are highly homoplastic yet phylogenetically informative in Hydrobiusini water scavenger beetles (Coleoptera: Hydrophilidae)

Phylogenetic analyses testing the monophyly of the tribe Hydrobiusini and the relationships among its genera are performed based on a data matrix including characters of larval morphology and morphometrics, larval chaetotaxy and adult morphology, including eight of the nine hydrobiusine genera plus 15 outgroup taxa. The head chaetotaxy of six genera of the tribe Hydrobiusini is described (Ametor, Hybogralius, Hydramara, Limnohydrobius, Limnoxenus and Sperchopsis). Morphometric characters derived from the head capsule and mouthparts are included. All characters are illustrated in detail. The analyses performed on the above datasets and their combinations reveal the monophyly of the Hydrobiusini except for Hybogralius, and reconstruct the internal topology of the tribe, largely corresponding to results of previous molecular analyses. Hybogralius groups with genera having larvae adapted to underwater feeding in all analyses. The position of the genus Tritonus within the Laccobiini is questioned by our analyses, which suggest a closer relationship with the tribes Hydrophilini or Hydrobiusini. Larval characters are revealed as highly homoplastic, with chaetotaxic characters performing slightly worse than usual larval morphology. Nonetheless, they are phylogenetically informative and useful for testing phylogenetic hypotheses resulting from analyses of molecules or adult morphology. A key to larvae of the genera of the Hydrobiusini is presented.

Going underwater: multiple origins and functional morphology of piercing-sucking feeding and tracheal system adaptations in water scavenger beetle larvae (Coleoptera: Hydrophiloidea)

Larvae of water scavenger beetles (Coleoptera: Hydrophiloidea) are adapted to a wide variety of aquatic habitats, but little is known about functional and evolutionary aspects of these adaptations. We review the functional morphology and evolution of feeding strategies of larvae of the families Hydrophilidae and Epimetopidae based on a detailed scanning electron microscope (SEM) analysis, analysis of video records of feeding behaviour and observations of living larvae. There are two main types of feeding mechanisms: chewing and piercing-sucking. The character mapping using the latest phylogenetic hypothesis for Hydrophiloidea infers the chewing system as the ancestral condition. The piercing-sucking mechanism evolved at least four times independently: once in Epimetopidae (Epimetopus) and three times in Hydrophilidae (Berosini: Berosus + Hemiosus; Laccobiini: Laccobius group; Hydrobiusini: Hybogralius). The piercing-sucking apparatus allows underwater extra-oral digestion and decreases the dependence of larvae on an aerial environment. A detailed study of the tracheal morphology of the piercing-sucking lineages reveals four independent origins of the apneustic respiratory system, all of them nested within lineages with piercing-sucking mouthparts. We conclude that piercing-sucking mouthparts represent a key innovation, which allows for the subsequent adaptation of the tracheal system, influences the diversification dynamics of the lineages and allows the shift to new adaptive zones.

Phylogeny, systematics and rarity assessment of New Zealand endemic Saphydrus beetles and related enigmatic larvae (Coleoptera : Hydrophilidae : Cylominae)

The New Zealand endemic beetle genus Saphydrus Sharp, 1884 (Coleoptera:Hydrophilidae:Cylominae) is studied in order to understand its phylogenetic position, species-level systematics, biology and distribution, and to reveal reasons for its rarity. The first complete genus-level phylogeny of Cylominae based on two mitochondrial (cox1, 16S) and two nuclear genes (18S, 28S) covering 18 of 19 genera of the subfamily reveals Saphydrus as an isolated lineage situated in a clade with Cylorygmus (South America), Relictorygmus (South Africa) and Eurygmus (Australia). DNA is used to associate two larval morphotypes with Saphydrus: one of them represents the larvae of S. suffusus Sharp, 1884; the other, characterised by unique characters of the head and prothorax morphology, is revealed as sister but not closely related to Saphydrus. It is described here as Enigmahydrus, gen. nov. with a single species, E. larvalis, sp. nov., whose adult stage remains unknown. Saphydrus includes five species, two of which (S. moeldnerae, sp. nov. and S. tanemahuta, sp. nov.) are described as new. Larvae of Enigmahydrus larvalis and Saphydrus suffusus are described and illustrated in detail based on DNA-identified specimens. Candidate larvae for Saphydrus obesus Sharp, 1884 and S. tanemahuta are illustrated and diagnosed. Specimen data are used to evaluate the range, altitudinal distribution, seasonality and population dynamics over time for all species. Strongly seasonal occurrence of adults combined with other factors (winter occurrence in S. obesus, occurrence at high altitudes in S. tanemahuta) is hypothesised as the primary reason of the rarity for Saphydrus species. By contrast, Enigmahydrus larvalis underwent a strong decline in population number and size since the 1970s and is currently known from a single, locally limited population; we propose the ‘nationally threatened’ status for this species. http://zoobank.org/urn:lsid:zoobank.org:pub:28D87163-29E8-418C-9380-262D3038023A