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Abstract Tailoring ultraconserved element (UCE) probe set design to focal taxa has been demonstrated to improve locus recovery and phylogenomic inference. However, beyond conducting expensive in vitro testing, it remains unclear how best to determine whether an existing UCE probe set is likely to suffice for phylogenomic inference or whether tailored probe design will be desirable. Here we investigate the utility of 8 different UCE probe sets for the in silico phylogenomic inference of scarabaeoid beetles. Probe sets tested differed in terms of (i) how phylogenetically distant from Scarabaeoidea taxa those used during probe design are, (ii) breadth of phylogenetic inference probe set was designed for, and (iii) method of probe design. As part of this study, 2 new UCE probe sets are produced for the beetle family Scarabaeidae and superfamily Hydrophiloidea. We confirm that probe set utility decreases with increasing phylogenetic distance from target taxa. In addition, narrowing the phylogenetic breadth of probe design decreases the phylogenetic capture range. We also confirm previous findings regarding ways to optimize UCE probe design. Finally, we make suggestions regarding assessment of need for de novo probe design. 

Abstract Sepidiini is a speciose tribe of desert-inhabiting darkling beetles, which contains a number of poorly defined taxonomic groups and is in need of revision at all taxonomic levels. In this study, two previously unrecognized lineages were discovered, based on morphological traits, among the extremely speciose genera Psammodes Kirby, 1819 (164 species and subspecies) and Ocnodes Fåhraeus, 1870 (144 species and subspecies), namely the Psammodes spinosus species-group and Ocnodes humeralis species-group. In order to test their phylogenetic placement, a phylogeny of the tribe was reconstructed based on analyses of DNA sequences from six nonoverlapping genetic loci (CAD, wg, COI JP, COI BC, COII, and 28S) using Bayesian and maximum likelihood inference methods. The aforementioned, morphologically defined, species-groups were recovered as distinct and well-supported lineages within Molurina + Phanerotomeina and are interpreted as independent genera, respectively, Tibiocnodes Gearner & Kamiński gen. nov. and Tuberocnodes Gearner & Kamiński gen. nov. A new species, Tuberocnodes synhimboides Gearner & Kamiński sp. nov., is also described. Furthermore, as the recovered phylogenetic placement of Tibiocnodes and Tuberocnodes undermines the monophyly of Molurina and Phanerotomeina, an analysis of the available diagnostic characters for those subtribes is also performed. As a consequence, Phanerotomeina is considered as a synonym of the newly redefined Molurina sens. nov. Finally, spectrograms of vibrations produced by substrate tapping of two Molurina species, Toktokkus vialis (Burchell, 1822) and T. synhimboides, are presented.