Rhinoncus

Stüben, Peter E., Schütte, André & Astrin, Jonas J., 2021, Barcoding and interspecific relationships of Macaronesian Weevils (Coleoptera: Curculionoidea), Beiträge Zur Entomologie = Contributions to Entomology 71 (1), pp. 127-135 : 133

Rhinoncus - morphologically castor, molecularly bruchoides

This case poses great puzzles for us. Even after multiple sequence analyses, the result was confirmed after collecting from two different sites on Madeira. The comparison with GenBank sequences also showed the same ‘molecular picture’: Rhinoncus bruchoides (HERBST 1784) . Likewise, the morphological classification based on the reliable identification features and undoubted differential diagnoses ( STÜBEN et al. 2012) as well as the verification by several experts resulted in a clear ‘morphological picture’: Rhinoncus castor (FABRICIUS 1792) . [The morphologically very similar species Rhinoncus bosnicus SCHULTZE, 1900 , which we were also able to sequence (2658-PSP|ZFMK), is out of the question here]. At this point, further speculations (e.g. transgression after hybridisation) are forbidden, as well as the suspicion that barcoding has reached its limits here. This case does not contain anything alarming or the search for quick explanations, but simply the request to resolve the contradiction through further research!

Conclusion

In view of the 468 of 735 Macaronesian weevils barcoded by us so far,only a few questions about so-called ‘molecular species’ that have so far eluded the morphological description (‘overlooked species’) must remain unanswered for the time being (for more comments see soon in STÜBEN, in press). In one species, namely the adelphotaxa Rhinoncus castor and R. bruchoides (Ceutorhynchinae) , contradictions arose during (re)identification. Furthermore, the samples sequenced from many islands and intra-island locations confirm the expected morphological placement for nearly each species in the Bayesian 50 % majority rule consensus tree (see electronic supplement, Fig. 2). As already PENTINSAARI et al. (2014) conclude in their study on nearly 1900 Northern European Coleoptera, CO 1 barcodes in particular not only lead to an almost certain re-identification of species and contribute to a remarkable differentiation of species, but also accelerate the discovery – in our case - of new weevil species on the Macaronesian islands. 150 years after the great discoveries of T.V. Wollaston, the hardly imaginable increase of new descriptions in the number of Entiminae and Cryptorhynchinae on all archipelagos of Macaronesia stands for this integrative taxonomic step in the last two decades ( MACHADO et al. 2017, STÜBEN 2018c).