Metopiorrhynchus Reitter, 1912

Christoph Germann, Sofia Wyler & Marco Valerio Bernasconi, 2017, DNA barcoding of selected alpine beetles with focus on Curculionoidea (Coleoptera), Revue suisse de Zoologie 124 (1), pp. 15-38 : 24

Subgenera Metopiorrhynchus Reitter, 1912 pars and Postaremus Reitter, 1912

In all our analyses ( Fig. 1 , Supp. 1), all the samples belonging to Otiorhynchus pupillatus Gyllenhal, 1834 clustered together with high bootstrap support. Otiorhynchus pupillatus is a highly polymorphic species. It varies in many characters as size, proportions (rostrum, pronotum and elytra), vestiture (e.g. form of scales, density), size of teeth on femora, and (female) genital organs. It reproduces almost strictly parthenogenetically; males are only known from the junior synonym teretirostris Stierlin, 1866 in the Seealps (mentioned by Stierlin in the description, but never revised since). The validity of several of the synonymous names is highly debated, part of them were recently resurrected in Magnano & Alonso-Zarazaga (2013). Such synonyms are subdentatus Bach, 1854 (described from Thuringia, Germany), frigidus Mulsant & Rey, 1859 (from the western Alps), cyclopterus F. Solari, 1946 (Tirol, Italy/ Austria, Bayern, Germany) and the before mentioned teretirostris.

Describing every single population as a separate species cannot be the goal of studying biodiversity [in the cases of parthenogenetically reproducing populations (unfertilized eggs producing only females, and apomixis, where no meiosis is involved) we have mostly nearly identical genotypes (but see also last section of this part)]. We therefore included 15 samples of O. pupillatus, which resulted in four roughly separable genetic lineages, where three of them differ in few substitutions, and a single specimen from Grisons (sample 085) differs substantially from all others (K2 distances: 0.073-0.086). There is no morphological match with any of the before mentioned debatable species or morphotypes. The first clade comprises samples from the Central and Eastern Swiss Alps (samples 0 28, 0 54, 0 55, 0 65, 0 75, 0 84, 0 97, 124 from Valais, bordering Italy and Grisons), the second one a specimen from the Val Mustair (sample 106), the third specimens from the Bernese Alps and Lower Engadine (samples 0 0 7, 0 12, 0 42, 0 74, 088), and the fourth one (the most differing, as already mentioned), a single specimen from Central Grisons (sample 085). Well supported sister to all samples of O. pupillatus is O. difficilis, an amphigonic, also morpholologically close standing species from northern Italy, Ticino up to the Valais in the Simplon region.

The same discrepancy between morphology and genetic lineages (the retrieved clades do not include specimens sharing the same set of characters) was observed in Otiorhynchus nodosus (O. F. Müller, 1764) belonging to the subgenus Postaremus (K2 distances 0.068-0.07, Table 4). Not less than 12 synonymous names belong to this highly variable, boreo-alpine species (colour of legs from black to red, shape of body, vestiture). As already mentioned for O. pupillatus, O. nodosus is also parthenogenetic in most of its area, and throughout the Swiss Alps.

In both species mentioned, the observed well separated clades may more likely mirror several post glacial immigration lineages. An alternative explanation would be that these asexually reproducing species represent complexes of species in statu nascendi in the sense of Dobzhansky & Spassky (1959). A phenomenon reported just recently from an identically parthenogenetically reproducing entimine weevil: Naupactus cervinus Boheman, 1840 in South America ( Rodriguero et al., 2013). Thereby the presence of different evolutionary units correlating with faint morphological and ecological differences could be shown, driven by many well-known evolutionary forces as mutation, selection, drift going along with geographic isolation. Whatsoever, naming these purely genetically recognisable evolutionary units/ populations will not (yet?) make sense, and unnecessarily blow up the taxonomy of Otiorhynchus . To gain a more complete insight into these complexes, definitely more samples from a broader geographical range and additional nuclear markers are needed.

Figures

Fig. 1. Best Maximum Likelihood tree as selected by MEGA) based on COI sequences of 142 samples of Curculionoidea (Chrysomelidae obtained by using MEGA 6. Values (over 50 %) of bootstrap support from 100 nodes.