Matthias Seidel

The peril of dating beetles

Recently, McKenna et al., 2015 (MCK15 hereafter) investigated the higher level phylogenetic relationships of beetles (Insecta, Coleoptera) using the most comprehensive molecular dataset to date, and inferred the absolute ages of major groups using multiple fossil calibrations across the beetle tree of life. Based on the result of their dating analysis, beetles diverged from Strepsiptera in the Early Permian c. 278.33 Ma with a 95% credibility interval (95% CI) of 288.28 to 271.89 Ma, and the crown age of Coleoptera was estimated for the Late Permian c. 252.89 Ma (95% CI: 267.68 to 238.78 Ma), supporting the view that beetles originated before and survived through the End-Permian Mass Extinction that occurred c. 252 Ma (Shen et al., 2011). However, some of the age estimates found in MCK15 are in conflict with current knowledge of the beetle fossil record (e.g. Nikolajev & Ren, 2010; Pan et al., 2011, Prokin & Ren, 2011; Fikáček et al., 2012a; Wang et al., 2013, 2014; Cai et al., 2014b, 2015a; Kirejtshuk et al., 2014; Boucher et al., 2016) and with other recently published molecular age estimates for some major beetle clades (e.g. Zhang & Zhou, 2013; Ahrens et al., 2014; Bloom et al., 2014; Kergoat et al., 2014; Kim & Farrell, 2015; Bocák et al., 2016; Gunter et al., 2016). In some cases, the difference in age estimates is significant and might change our understanding of the mode and tempo of diversification dynamics of these groups. Based on a careful examination of the data and analyses performed in MCK15, we propose that the divergence time estimates which they found are likely to underestimate clade ages. We believe this is due to the subset of fossil Coleoptera that MCK15 selected as calibration points, as well as the methodological approach used in their analyses. To explore the impact of fossil selection on the age of Coleoptera, we derived an alternative set of fossil calibration points based on best-practice recommendations (e.g. Parham et al., 2012),

A review of the Cercyon Leach (Coleoptera, Hydrophilidae, Sphaeridiinae) of the Greater Antilles

Abstract The representatives of the genus Cercyon Leach occurring in the Greater Antilles are reviewed. Ten species are recorded, of which five are described here as new: C. gimmeli sp. n. (Dominican Republic), C. armatipenis sp. n. (Dominican Republic), C. taino sp. n. (Dominican Republic), C. sklodowskae sp. n. (Jamaica) and C. spiniventris sp. n. (Dominican Republic). Diagnoses and detailed distributional data are also provided for C. floridanus Horn, 1890 (distributed in southeastern United States of America and Cayman Islands), C. insularis Chevrolat, 1863 (endemic to the Antilles) C. praetextatus (Say, 1825) (widely distributed in the New World incl. Greater Antilles), C. quisquilius (Linnaeus, 1761) (an adventive species of Paleartic origin) and C. nigriceps (Marshall, 1802) (an adventive species probably of Oriental origin). Cercyon armatipenis, C. gimmeli, C. taino form a group of closely related species only distinguishable by male genitalia and DNA sequences. A key to the Great Antillean Cercyon is provided and important diagnostic characters are illustrated. The larvae of C. insularis and C. taino were associated with adults using COI barcode sequences, illustrated and diagnosed. Full occurrence data, additional images and COI barcode sequences were submitted to open access on-line depositories in an effort to provide access to complete data.

Morphology and biology of the flower-visiting water scavenger beetle genus Rygmodus (Coleoptera: Hydrophilidae): Morphology and biology of Rygmodus

Hydrophilidae (water scavenger beetles) is well known as an aquatic beetle family; however, it contains ca. 1,000 secondarily terrestrial species derived from aquatic ancestors. The New Zealand endemic genus Rygmodus White is a member of the hydrophilid subfamily Cylominae, which is the early‐diverging taxon of the largest terrestrial lineage (Cylominae + Sphaeridiinae) within the Hydrophilidae. In this paper we report that Rygmodus beetles are pollen‐feeding flower visitors as adults, but aquatic predators as larvae. Based on analyses of gut contents and a summary of collecting records reported on museum specimen labels, adult Rygmodus beetles are generalists feeding on pollen of at least 13 plant families. Rygmodus adult mouthparts differ from those of other (saprophagous) hydrophilid beetles in having the simple scoop‐like apex and mola with roughly denticulate surface, resembling the morphology found in pollen‐feeding staphylinid beetles. Larvae were found along the sides of streams, under stones and in algal mats and water‐soaked moss; one collected larval specimen was identified using DNA barcoding of two molecular markers, mitochondrial cytochrome oxidase 1 (cox1) and nuclear histone 3 (H3). Larvae of two species, Rygmodus modestus and Rygmodus sp., are described in detail and illustrated; they closely resemble ambush‐type predatory larvae of the hydrophilid tribe Hydrophilini in the head morphology. Rygmodus is the only known hydrophilid beetle with adults and larvae inhabiting different environments.

Breaking a Disjunct Distribution: A Review of the Southern Hemisphere Genera Cylorygmus and Relictorygmus gen. nov. (Hydrophilidae: Cylominae)

Abstract. The southern hemisphere water scavenger beetle genus Cylorygmus Orchymont, 1933 (Coleoptera: Hydrophilidae: Cylominae) is revised. Three species are recognized, one in Chile and two in South Africa. The morphological differences indicate that the African species are not congeneric with the Chilean one. Relictorygmus gen. nov. is established for the African R. trevornoahi sp. nov. (type species) and R. repentinus (Hebauer, 2002), both known from few localities in the Western Cape province of the Republic of South Africa. The genus Cylorygmus with the only species C. lineatopunctatus Orchymont, 1933 is endemic to a small region in central Chile. Its larva is described in detail based on specimens collected in association with adults. Both genera and all species are diagnosed, described and illustrated, and an identification key for adults is provided. Our study demonstrates that the trans-Atlantic disjunct distribution of Cylorygmus was based on inaccurate taxonomic treatment and did not reflect the real evolutionary history of these beetles.

On Neotropical Merophysiinae with descriptions of a new genus and new species (Coleoptera, Endomychidae)

Abstract Intensive survey of museum collections and new field collecting resulted in discovery of six new, closely related species of the Neotropical Merophysiinae. A new species of the genus Lycoperdinella Champion, L. boliviensis sp. n., from Bolivia and Brazil, and five new species from Mexico for which a new genus is proposed here as Rueckeria gen. n.: R. inecol (type species), R. nigrileonis, R. ocelotl, R. puma, R. skelleyi spp. n., have been discovered. Lycoperdinella, Rueckeria gen. n., L. subcaeca Champion and all new species are diagnosed, described, and illustrated. Keys to the species of Lycoperdinella and Rueckeria and a distribution map are provided. A lectotype of Lycoperdinella subcaeca Champion, 1913 is designated. Molecular barcodes of three new species of Rueckeria are provided in order to help with the identification of these taxa.