Cionus griseus versus

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 : 131

Cionus griseus versus C. variegatus - or just a very variable species?

Both species occur on Tenerife (apparently only at different altitudes, unclear from the present data). The molecular analysis of the CO1 gene is clear: Two completely differently coloured Cionus species on two different endemic Scrophulariaceae - namely Scrophularia glabrata and Scrophularia smithii langeana - can be distinguished morphologically from their markings but not molecularly (p-distance <0.9 %)! Therefore, the initial suspicion is that Cionus griseus on Tenerife could be a younger synonym of Cionus variegatus . So the first author searched for more specimens on the other Canary Islands and found C. variegatus on La Gomera on the introduced Scrophulariaceae Verbascum virgatum ; a first indication that there is not necessarily a strict host plant link on every island. Molecularly, the small p-distances of these specimens in comparison to the specimens on Tenerife do not speak in favour of a species distinct from C. griseus (<1.7 %). However, clearly different from this - in a sister clade - are the specimens of C. griseus / variegatus on La Palma (p-distances: 3.8 % - 4.4 %), and this shows the full extent of the morphological confusion: due to the colour pattern it is difficult to tell which of the two species we are dealing with ( Fig. 3 ). On the other hand, it cannot be conclusively clarified at the mitochondrial level, whether it is actually a case of introgression after hybridization on La Palma and Tenerife. This in turn would make a claim for a very young species separation. However, this requires further extensive molecular nuclear gene studies. Interim conclusion: The whole matter may be much more complex and difficult than the different colour patterns (of colour morphs?) in exclusively morphological studies suggest (KOSTAL & CALDARA 2019).

Figures

Fig. 3: The colour variants of Cionus griseus x variegatus in a single population on La Palma (Jedey). Is this a case of introgression