Dichotrachelus orobicus Meregalli, Monguzzi & Kahlen, 2021

Meregalli, Massimo, Kahlen, Manfred, Monguzzi, Riccardo, Rossi, Valentina Marzia & Santovito, Alfredo, 2021, A new cryptic species of Dichotrachelus from the Bergamasque Prealps, a late Miocene centre of speciation for the alpine fauna (Coleoptera: Curculionidae: Cyclominae), Arthropod Systematics & amp; Phylogeny 79, pp. 281-293 : 281

Dichotrachelus orobicus Meregalli, Monguzzi & Kahlen sp. n.

Type locality.

Italy, Lombardy, Prov. Bergamo, Val di Scalve, Pizzo Camino

Derivation of the name.

Named after the Prealpi Orobie, the Bergamasque Prealps, a mountain range in the Italian Alps, located in northern Lombardy.

Diagnostic description.

A cryptic species vicariant of Dichotrachelus grignensis , morphologically extremely similar, only different for the shape of the male genital sclerite (Figs 1 - 3 ) (in parenthesis the comparison of the same characters in D. grignensis , see also table of morphological characters in Results, Morphological analysis, 3.1).

Body length of the holotype: 6.85 mm. Rostrum narrow, ratio length/width at base 1.65, with sides in dorsal view subparallel, weakly convergent anteriad, with deep interantennal longitudinal groove (rostrum broad, mean ratio length/width at base 1.37; dorsal sides linearly convergent from base to antennal insertion, longitudinal groove very shallow). Pronotum small, slightly constricted near apex with sides moderately curvilinear (pronotum robust, not constricted near apex, sides usually slightly linearly broadened from base to apical third). Elytral shape very similar between the two species. Tarsomere 3 of protarsus as long as wide, lobes slightly developed (tarsomere 3 of protarsus shorter than wide, lobes not developed); tarsomere 3 of metatarsus as long as wide (tarsomere 3 of metatarsus shorter than wide). Sides of body of penis smoothly restricted anteriad, lamella with parallel sides, broadly rounded at apex (sides of body of penis sharply restricted anteriad, distinctly sinuate before lamella, lamella with sides feebly convergent anteriad, slightly elongated at apex). Anterior valve of male genital sclerite (terminology as in Meregalli et al. 2013) in lateral view oblong, much longer than wide, posterior valve small, semicircular, external margin strongly curved (anterior valve oval, broadly expanded, scarcely longer than wide, posterior valve large, oval, external margin scarcely rounded).

Variability.

The specimens from Pizzo Camino area are relatively uniform, particularly in the discriminating characters. Those from Pizzo Arera have the rostrum slightly shorter and broader. Those from Presolana have the rostrum similar to those from Pizzo Camino. The specimen from Resegone has the apex of the penis more similar to those of the Grigna massifs, but the genital sclerite has the typical shape of D. orobicus .

Type material

(approximate georeference, when not indicated on label, in square parenthesis). Labels reported verbatim; /: different line. Holotype ♂. "Val di Scalve, Schilpario / (BG) Pizzo Camino [45.9867°, 10.1810°] / m 2000 22.VII.2002 / R. Monguzzi leg." (deposited at Museo Civico di Storia Naturale, Milano, Italy). Paratypes: coll. Monguzzi: same data as the holotype, 1♂, 1♀; "Pizzo Camino / Val di Scalve, Schilpario - BG / m 2000 5.VIII.1979 / Leg. R. Monguzzi" 1♀; "Pizzo Camino (BG) / Schilpario m 2000 / 4.VIII.2000 / R. Monguzzi" 1♀; "Pizzo Camino / (Schilpario) / m 2100 17.VIII.2014 / R. Monguzzi" 1 fragment; "Val di Scalve (BG) / Cimone d. Bagozza [46.0214°, 10.2662°] / m 2100 6.09.2014 / R. Monguzzi leg." 3♀; "Val di Scalve (BG) / Mass Presolana / M. Ferrante m 2200 [45.9744°, 10.0288°] / 13.9.14 R. Monguzzi" 1♀; "Prealpi Orobie (BG) / M Ferrante m 2300 / vers. Est Gruppo della / Presolana 19.07.2014 / R. Monguzzi leg." 1♀; "Pizzo Arera (BG) / Mandrone m 2100 [45.9305°, 09.8067°] / 30.vi.09 R. Monguzzi" 1♀; "M. Arera / BG m 2200 / 11.7.81 Rosa" 1♂; "Prealpi Bergamasche / Val Brembana Cima / di Menna [45.9254°, 09.7595°] m 2100 / 20.08.2013 R. Monguzzi"; "Prealpi Bergamasche / Zuccone dei Campelli [45.9580°, 09.5133°] / Vers. Valsassina (LC) / Valle dei Camosci m 2100 / 3.vi.09 R. Monguzzi" 2♀.

Coll. Kahlen: "Prov. Bergamo, Pizzo Arera, Mandrone 2000m 45°56′04″N, 9°48′13″E, 7.7.1990 Saxifraga caesia ", 2♂ 2♀; "Prov. Bergamo, Pizzo Arera, SW-Kar 2050m 45°55′50″N, 9°48′24″E, 20.7.1992, Saxifraga caesia " 2♂ 1♀; "Prov. Brescia, Passo di Baione 2155m 46°01′17″N, 10°15′59″E, 30.7.2018 Saxifraga caesia " 1♀.

Coll. Szallies: "I Alpi Bergam. / Pizzo Arera Ost- / grat Nordkar / 23-/2500 m 3.6.2015 / leg. Szallies" 1♂; "I. Bergam. Alpen / Valle Camonica / Passo di Baione [46.0213°, 10.2666°] / 2150 m 27.7.2016 / leg. Szallies" 3♂; I. Bergam. Alpen / Valle Camonica / Cima dei Ladrinai [46.0165°, 10.2790°] / 2300 m 27.7.2016 / leg. Szallies" 1♀.

Coll. Meregalli: "Val di Scalve, Schilpario / (BG) Pizzo Camino / m 2000 22.VII.2002 / R. Monguzzi leg." 1♂ 1♀.

Non-type material. "I Bergamask Alpen / Lecco Resegone / 1800 m / 1.7.2016 / leg. Szallies" 1♂ (aedeagus only, body mistakenly destroyed during DNA extraction).

Distribution.

Dichotrachelus orobicus is present in all the calcareous mountains between Valsassina and Valcamonica, where it is usually found above 1800 m asl. (Fig. 8 ).

Biology.

The species is monophagous on Saxifraga caesia . The larvae develop among the roots of Saxifraga , often on clumps growing on the soil (Zuccone Campelli, Presolana). The adults feed on the same plant. Their activity is nocturnal, when they can be found in trophic activity on the plants and walking on the surrounding rocks; during the day they shelter below stones and in rock crevices.

Conservation status.

Dichotrachelus orobicus does not seem to be endangered at present and it does not fully meet any of the criteria required for inclusion in the categories at risk ( IUCN 2001, 2012). It would be classified as Vulnerable according to Crit. B2(a): severely fragmented species known in between 5 and 10 populations, but none of conditions (b) or (c) ( IUCN Standards and Petitions Committee 2019) appear to be applicable, at least at present. However, possible effects of global warming and rainfall rate variation may influence vegetation in the near future, and these weevils, so highly stenoecious and ecologically very specialized, are probably incapable of adaptation to changes of their niche. Single populations might indeed be at risk, in particular that from Resegone, a mountain that reaches only 1875 m a.s.l. and has suitable habitats of very limited extension.

Figures

Figure 1. Dichotrachelus orobicus. Holotype.

Figure 3. Male genital sclerite. Dichotrachelus orobicus, paratype (a). Dichotrachelus grignensis, Northern Grigna (b).

Figure 8. Dichotrachelus orobicus and D. grignensis, distribution map. Map data: Google Earth, Maxar Technologies, used according to Google Earth Terms of Service.