Abstract.  Morphological characters and molecular sequence data were for the first time analysed separately and combined for the true water bugs (Hemiptera–Heteroptera, infraorder Nepomorpha). Data from forty species representing all families were included, together with two outgroup species representing the infraorders Gerromorpha and Leptopodomorpha. The morphological data matrix consisted of sixty‐five characters obtained from literature sources. Molecular data included approximately 960 bp from the mitochondrial gene 16S and the nuclear gene 28S for all forty‐two terminal taxa. The morphological dataset was analysed using maximum parsimony and the combined morphological and molecular (16S + 28S rDNA) dataset was analysed using direct optimization. A sensitivity analysis of sixteen different sets of parameters (various combinations of insertion–deletion cost and transversion costs) was undertaken. Character congruence was used as an optimality criterion to choose among competing phylogenetic hypotheses. The final hypothesis was obtained from the analysis of the combined molecular and mor phological dataset with the most congruent parameter set. This hypothesis supports the monophyly of all currently recognized families of Nepomorpha, and of the superfamilies Nepoidea (Nepidae + Belostomatidae), Corixoidea (Corixidae), Ochteroidea Ochteridae + Gelastocoridae), Notonectoidea (Notonectidae), and Pleoidea (Pleidae + Helotrephidae), but not the monophyly of the Naucoroidea (Naucoridae + Aphelocheiridae + Potamocoridae). The close relationship between the Notonectidae and Pleoidea is also supported. Our hypothesis concurs with Mahner in the placement of the Corixidae as a sister group to the remaining nepomorphan superfamilies except the Nepoidea, but differs in the placement of the Ochteroidea as a sister group to the Notonectoidea + Pleoidea. The superfamily Naucoroidea should be limited to only including the family Naucoridae and not the families Aphelocheiridae and Potamocoridae. The present analysis strongly supports a sister group relationship between the families Aphelocheiridae and Potamocoridae, a monophylum for which we propose a new superfamily, Aphelocheiroidea.

The primarily Holarctic pond skater genus Gerris Fabricius is redescribed and compared with two other northern temperate water strider genera, Aquarius Schellenberg and Limnoporus Stål. The subgenus Gerriselloides Hungerford and Matsuda is redefined and Macrogerris subgen.nov. is described to hold a group of eight eastern Palearctic species. Monophyletic species-groups of the subgenus Gerris s.str. are diagnosed and their species composition is delimited. Gerris brevirostris Bergroth is synonymized with G. lacustris (L.), syn.nov. Keys for identification are provided for all species of Gerris. The phylogenetic relationships among species of Limnoporus, Aquarius, and Gerris are analyzed. The data set comprises 63 structural characters coded for 2 species of Limnoporus, 7 species of Aquarius, and 19 species of Gerris. In particular, the metathoracic scent apparatus, male genitalia, female ovipositor, and gynatrial complex reveal characters of phylogenetic importance. The data set is subjected to cladistic analyses using the parsimony program Hennig86. Character polarities are determined using either a hypothetical taxon or the species Gigantometra gigas (southeastern Asia) as out-group. Through cladistic analysis, evidence is brought forward supporting one particular hypothesis of the relationships between Aquarius, Limnoporus, and Gerris, and between subgenera and monophyletic species-groups of Gerris. The reconstructed phylogeny is used to infer evolutionary sequences in patterns of wing polymorphism, habitat preferences, and sexual size dimorphism among temperate water striders, and to discuss their geographical distribution and historical biogeography.

BackgroundPatients with primary sclerosing cholangitis (PSC) display an altered colonic microbiome compared with healthy controls. However, little is known on the bile duct microbiome and its interplay with bile acid metabolism in PSC.MethodsPatients with PSC (n=43) and controls without sclerosing cholangitis (n=22) requiring endoscopic retrograde cholangiography were included prospectively. Leading indications in controls were sporadic choledocholithiasis and papillary adenoma. A total of 260 biospecimens were collected from the oral cavity, duodenal fluid and mucosa and ductal bile. Microbiomes of the upper alimentary tract and ductal bile were profiled by sequencing the 16S-rRNA-encoding gene (V1–V2). Bile fluid bile acid composition was measured by high-performance liquid chromatography mass spectrometry and validated in an external cohort (n=20).ResultsThe bile fluid harboured a diverse microbiome that was distinct from the oral cavity, the duodenal fluid and duodenal mucosa communities. The upper alimentary tract microbiome differed between PSC patients and controls. However, the strongest differences between PSC patients and controls were observed in the ductal bile fluid, including reduced biodiversity (Shannon entropy, p=0.0127) and increase of pathogen Enterococcus faecalis (FDR=4.18×10−5) in PSC. Enterococcus abundance in ductal bile was strongly correlated with concentration of the noxious secondary bile acid taurolithocholic acid (r=0.60, p=0.0021).ConclusionPSC is characterised by an altered microbiome of the upper alimentary tract and bile ducts. Biliary dysbiosis is linked with increased concentrations of the proinflammatory and potentially cancerogenic agent taurolithocholic acid.

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