Taxonomy, phylogeny and biogeography of Central European "Kybos" (Insecta: Hemiptera: Cicadellidae)

The Central European species of the taxonomically difficult Holarctic typhlocybine genus Kybos are revised with morphological, molecular and bioacoustic methods. Currently it is impossible to identify females and nymphs. In addition the otherwise diagnostic shape of the male genitalia is linked by intermediates in some morphologically similar nominal species. The second important diagnostic structure, the male sound apodemes, is not yet fully developped in teneral males, a fact which was not sufficiently taken into consideration by some authors. The present study evaluates the morphological variation of the male genitalia and sound apodemes. Females and nymphs are investigated for taxonomically relevant characters. For comparison molecular studies using sequences of the so called barcoding gene COI as well as 16S are performed and bioacoustic characters are investigated for some species. The morphological studies did not yield previously unknown characters particularly for the females and nymphs but suggested that the variation of the male genitalia has previously been overestimated. For this reason K. perplexus is synonymised with K. strigilifer (new synonymy). Similarly the small sound apodemes of K. volgensis are interpreted as not yet fully developped structures and the species is synonymised with K. virgator (new synonymy). The base of the female ovipositor is variable within Kybos and separates species groups but does not diagnose species. Nymphs vary in leg dimensions and colour forming the same species groups as the female genitalia but, again, do not diagnose species. In the molecular analyses neither COI nor 16S sequences could discriminated all the species defined by morphology. In particular K. butleri and K. rufescens were polyphyletic in both molecular analyses. These results clearly illustrate that the so called barcoding gene COI is not universally applicable for species definition. The few results from the bioacoustic studies indicate that this method may be helpful to solve some taxonomic problems of closely related sympatric species. Phylogenetic analyses are performed with morphological data and COI as well as 16S sequences. The three analyses strongly support the monophyly of Kybos. The consensus trees of the three analyses are poorly resolved and their topologies differ from each other. In the morphological tree the female genital characters make the most important contribution to tree structure whereas the male genitalia are of less importance, contrary to species diagnoses. It is interesting to note that the morphological tree comprises a monophyletic group of Betulaceae feeders not supported by the molecular trees.