An Integrative Revision of the Genus Rhamphus (Curculionidae) from the Western Palearctic: Morphological and Molecular Data Reveal the Radiation of Multiple Species

Here, we report on the complexity of the taxonomy and species evolution within the monophyletic genus <i>Rhamphus</i>, which includes some of the smallest members of the Curculionidae family and whose species are morphologically almost indistinguishable from each other. Despite their similar appearance, we found high divergence and varying evolutionary rates among observed species groups living both in sympatry and allopatry in the western Palearctic. On the basis of subtle morphological differences and molecular evidence, we defined eight morphotypic groups and 14 species, of which 6 are newly described in this paper: <i>R. diottii</i><b>sp. nov</b>. and <i>R. ibericus</i><b>sp. nov.</b> (<i>monzinii</i>-group), <i>R. cypricus</i><b>sp. nov.</b> and <i>R. macedonicus</i><b>sp. nov.</b> (<i>cypricus</i>-group), <i>R. betulae</i><b>sp. nov.</b> and <i>R. crypticus</i><b>sp. nov.</b> (<i>pulicarius</i> group). <i>Rhamphus</i> morphotypic groups showed intense species radiation and cryptic speciation, with an estimated genetic divergence of 4.2-18.8% (uncorrected) in the barcoding region of the mitochondrial <i>COI</i> gene. The estimated divergence of the two nuclear markers, n<i>EF-1α</i> and n<i>CAD</i>, ranged from 1 to 11.9% and 0.5 to 15%, respectively. Phylogenetic analyses using both single and partitioned multigene adequately resolved the relationships between <i>Rhamphus</i> species and identified all groups and the species with high nodal support. According to our study, <i>Rhamphus</i> species cluster into monophyletic groups that are partly defined by their host plant associations and by subtle differences in penis shape. No substantial differences in female genitalia were found. Most of the species exhibit relatively rapid species radiation, which is cryptic by nature.