Dorcadion equestre

Dascălu, Maria-Magdalena, Caba, Florina-Georgiana & Fusu, Lucian, 2022, DNA barcoding in Dorcadionini (Coleoptera, Cerambycidae) uncovers mitochondrial-morphological discordance and the hybridogenic origin of several subspecies, Organisms Diversity & Evolution (New York, N. Y.) 22 (1), pp. 205-229 : 222-223

Dorcadion equestre

Unfortunately, we could not include in the molecular analyses specimens from the type locality of D. equestre . The species was described from ‘South Russia’ which at the end of the eighteenth century also stretched over present-day Ukraine, where the species is quite widespread (Zagaykevich & Puchkov, 2009), but it is also distributed in present day south of European Russia ( Plavilstshikov, 1958). There is no disruption in the species distribution in Ukraine, NE Romania and Republic of Moldova, but a distribution break exists between the above-mentioned area and the populations from the Romanian Plane (Walachia) and Transylvania, type locality for D. equestre transsilvanicum ( Fig. 6 ). This break along the Iaşi escarpment was most likely generated by the historically heavily forested northern part of the Bârlad Plateau. Due to the large genetic divergence between specimens from these two disjunct areas, we include specimens from NE Romania and Republic of Moldova in the nominotypical subspecies rather than in D. equestre transsilvanicum as done by Danilevsky (2020) and Pesarini and Sabbadini (2010). In these specimens, the development of dorsal carinae and the presence of black mottling, characters that differentiate the two subspecies ( Pesarini & Sabbadini, 2013), are more similar to specimens from Ukraine (based on 9 specimens in first author’s collection), than to those from southern Romania.

scale. A portion of the ITS2 trace file for three specimens is included, showing double peaks in linPro1001 for the positions where the parental species differ. Scale bar represents 1 mm

In our GMYC species delimitation scenario, D. equestre transsilvanicum is delineated as a distinct species from the specimens we identified as nominotypical. The two groups are separated by a minimum of seven substitutions (Fig. 3). The analysis also included one specimen from Dobrogea, an area lying south of the Danube. It is differentiated as a potentially distinct species only by the multiple-threshold GMYC, being included in the nominotypical subspecies by the singlethreshold approach ( Fig. 2 , GMYCs and GMYCm). The PTP approach, on the other hand, is not delineating D. equestre transsilvanicum and D. equestre equestre as two species ( Fig. 2 , PTP and mPTP). A common result for all methods is the delimitation of D. equestre reclinatum as a distinct species because it is as divergent from the nominotypical subspecies as, for example, the divergence between D. aethiops and D. fulvum . Since for this subspecies our analysis included only one sequence derived from another study ( Giannoulis et al., 2020), more sampling from a larger area might narrow this gap. A large intraspecific divergence was also found in other 16 species of European Cerambycidae ( Hendrich et al., 2015; Rougerie et al., 2015).

Figures

Fig.6 North-western distribution limit of D. equestre. Black circles: D. equestre equestre, red circles: D. equestre transsilvanicum. Yellow crosses: localities for the barcoded specimens. Distribution based on published localities, first author collection and other public collections

Fig. 2 Maximum clade credibility ultrametric tree generated with Bayesian inference in BEAST from 162 Dorcadionini COI sequences (152 from this study, 10 from GenBank). Clades with numerous sequences and no delimitation issues are collapsed, with numbers