A review of Pseudorygmodus (Coleoptera: Hydrophilidae), with notes on the classification of the Anacaenini and on distribution of genera endemic to southern South America

Abstract: The morphology and taxonomy of the genus Pseudorygmodus Hansen, 1999 endemic to Chile is reviewed based on freshly collected material and museum specimens. Two species are recognized: P. flintispangleri (Moroni, 1985) widespread from Los Lagos Region to Magallanes Region, and P. versicolor sp. nov. which is only known from Parque Nacional Nahuelbuta in La Araucanía Region. A phylogenetic analysis is performed to reveal the position of the genus within Hydrophilidae, based on four genes (cox1, cox2, 18S and 28S). The results reveal that Pseudorygmodus is a member of the tribe Anacaenini of the subfamily Chaetarthriinae, which is supported by both adult and larval morphology. Within Anacaenini, it was placed in the Anacaena Thomson, 1859 clade, which is supported by the morphology of the nasale of the larva. The phylogenetic analysis performed here as well as the morphological comparison of larvae of the Anacaenini brought additional evidence supporting the internal topology of the tribe, including the polyphyly of Anacaena in the current sense. The genus Crenitulus Winters, 1926, stat. restit., is hence reestablished for the former Anacaena suturalis group, containing the following species: C. attiguus (Orchymont, 1942) comb. nov., C. hirsutus (Komarek, 2005) comb. nov., C. nitens (Gentili, 1993) comb. nov., C. paleodominicus (Fikáček & Engel, 2011) comb. nov., C. perpennus (Orchymont, 1942) comb. nov., C. solstitialis (Kirsch, 1873) comb. nov., C. schoedli (Komarek, 2005) comb. nov., and C. suturalis (LeConte, 1866). The genus Gentilina Hebauer, 2003, syn. nov., is synonymized with Crenitulus. A potential distribution is modelled for five hydrophilid genera endemic to southern South America (Andotypus Spangler, 1979, Anticura Spangler, 1979, Cylorygmus Orchymont, 1933, Hydramara Knisch, 1925 and Pseudorygmodus) using the high-resolution climatic data and the maximum entropy approach, in order to focus the future collecting effort to the areas where the genera likely occur. Biology and distribution of Pseudorygmodus and other endemic austral genera is briefly discussed, as well as problems that should be focused in future phylogenetic studies of the Chaetarthriinae and Anacaenini.

Key words: Hydrophilidae, Rygmodinae, Chaetarthriinae, Anacaenini, Hydrophilinae, Hydrobiusini, taxonomy, morphology, DNA, phylogeny, new species, new combination, ecological niche modeling, relict, Argentina, Chile, austral South America, Neotropical Region