Canthidium quercetorum Kohlmann, Arriaga-Jiménez & Rös, 2018

Kohlmann, Bert, Arriaga-Jiménez, Alfonsina & Rös, Matthias, 2018, An unusual new species of Canthidium (Coleoptera: Scarabaeidae: Scarabaeinae) from Oaxaca, Mexico, Zootaxa 4378 (2), pp. 273-278 : 273-277

Canthidium quercetorum Kohlmann, Arriaga-Jiménez & Rös , new species ( Figs. 1–3 .)

Diagnosis. This species is distinguished by the following combination of characters: body sub-globose and dorsally dark green in colour; head and pronotum uniformly and strongly punctate; frons swollen; frontoclypeal region with a small, smooth swelling medial to each eye; eye dorsally at posterior end of gena two facets wide, interocular distance separated by approximately 14–16 times maximal eye width; antennal lamellae black and sericeous; pronotal surface smooth with sparse micropunctures, basal pronotal border not margined; elytra with eight clearly punctate striae, surface shagreen; pygidium shagreen and lightly punctate; the inner apical margin of the female protibia is not projected at all.

Type locality. Mexico: Oaxaca: Reserva Comunitaria San Pablo Etla.

Description of holotype. Length: 5.1 mm, humeral width: 3.5 mm. Body form sub-globose ( Figs. 1 , 2A–C ). Head and pronotum dark green and shiny, elytra brownish black with green reflections ( Fig. 2A ). Head and pronotum strongly punctate and devoid of setae.

Clypeus rugosely punctate, apex strongly bidentate, median emargination broadly V-shaped; eye dorsally narrow 8– 9 facets at widest portion, at posterior end of gena very narrow, two facets wide, eyes separated approximately 14–16 times maximum eye width ( Fig. 2A ). Head, frons, and vertex strongly punctate; frons swollen; two small, black, smooth swellings between the eyes ( Fig. 2A ). On either side of the vertex midline a small impunctate, shagreen area is present. Head surface lightly shagreen at base. Antennae blackish sericeous.

Pronotum with smooth surface, sparse micropunctures, shiny, and strongly and uniformly punctate ( Fig. 2A ); lateral fovea inconspicuous and simple; posterior margin lacking elongate punctures or groove.

Elytral striae consisting of clear shallow, thin lines, interrupted by fairly evenly spaced oval punctures (spacing approximately at 3–5 the maximum length of one puncture); intervals finely punctate; surface shagreen ( Fig. 2A ).

Proepisternum excavate anteriorly, surface shagreen and finely punctate. Sternellum shagreen and with a line of setiferous punctures along base. Mesosternum shagreen and finely punctate. Metasternum punctate, less so at the midline ( Fig. 2B ), lateral-lobe punctures forming coarse rugulae.

Sternites 3–6 shagreen, sternites 3–5 with a row of small punctures along front border ( Fig. 2B ).

Protibia with three teeth on external border, inner apical margin of protibia produced into a triangular anterior projection and slightly bent downwards; apical spur simple and straight ( Fig. 2D ). Profemora, mesofemora, and metafemora with ventral surface finely punctate and finely shagreen.

Pygidium slightly convex, shagreen, and shiny with very fine and shallow punctures ( Fig. 2F ). Aedeagus as in Fig. 2G .

Allotype. Female. Length: 4.6 mm, humeral width: 3.4 mm. Differing from the male in the following major characters: shorter pygidium, last abdominal segment broader, inner apex of protibia not forming a triangular projection, and tip of apical spur slightly bent inwards ( Fig. 2E ).

Variation. Length: 3.9–5.4 mm, humeral width: 2.4–3.7 mm. Dorsal surface reflexions varies from green to coppery. Antennal lamella varies from black to dark brown. Elytral intervals vary from flat to slightly convex.

Material examined (110 specimens). Holotype. Male: “ México . Oaxaca: Reserva Comunitaria San Pablo Etla. 20- IX-2016. Coprotrampa. x- 96.732348’ W, y- 17.170968’ N. Bosque de Encino, 2155 m. Arriaga, J.A., Col.” Allotype. Female. “ México . Oaxaca: Reserva Comunitaria San Pablo Etla. 20-IX-2016. Coprotrampa. x- 96.732348’ W, y- 17.170968’ N. Bosque de Encino, 2155 m. Arriaga, J.A., Col. ” Paratypes: “ México . Oaxaca: Reserva Comunitaria San Pablo Etla. 20-IX-2016. Coprotrampa. x- 96.732348’ W, y- 17.170968’ N. Bosque de Encino, 2155 m. Arriaga, J.A., Col. ” (102 specimens, IEXA (50) , MNHN (12), CMNC (20), CEMT (20)); “ México . Oaxaca: Reserva Comunitaria San Pablo Etla. 20-IX-2016. Coprotrampa. x- 96.732386’ W, y- 17.170454’ N. Bosque de Encino, 2151 m. Arriaga, J.A., Col. ” (3 specimens, IEXA); “ México . Oaxaca: Reserva Comunitaria San Pablo Etla. 20-IX-2016. Coprotrampa. x- 96.733014’ W, y- 17.170797’ N. Bosque de Encino, 2133 m. Arriaga, J.A., Col. ” (1 specimen, IEXA); “ México . Oaxaca: Reserva Comunitaria San Pablo Etla. 20-IX-2016. Coprotrampa. 23-IX-16, x- 96.725987’ W, y- 17.174158’ N. Bosque de Encino, 2271 m. Arriaga, J.A., Col. ” (2 specimens, IEXA).

Geographical distribution. The species is so far only known from Etla in the Sierra Norte in Oaxaca ( Fig. 3A ), along the internal dry slope facing the Oaxaca Valley. The dry deciduous oak forest where Canthidium quercetorum was found is characterized by trees between 5–10 m in height, and with around 12 cm diameter at breast height ( Figs. 3B–C ). Abundant oak species limited to this vegetation type are Quercus laeta Liebm. and Q. laurina Humb. & Bonpl. (Fagaceae) , which in this region is distributed principally between 1800–2400 m. Other species dominating this forest in the sampling site are Q. glaucoides Mart. & Gal. , Q. liebmannii Oersted. , Q. rugosa Née , and Q. castanea Née , which are also found at higher or lower altitudes (John Williams, Centro Interdisciplinario de Investigación para el Desarrollo Integral Regional, Oaxaca, personal communication; Valencia-Ávalos & Nixon 2004). This dry deciduous oak forest shows a strong seasonality, where most trees lose their leaves for around four to five months between December and May ( Figs. 3B–C ). As can be seen ( Fig. 3D ), the inferred area of distribution of this new species is adjacent to the Oaxaca Metropolitan Area. Thankfully, the area is under protection as the San Pablo Community Reserve.

This species has been collected in the forest in association with Canthon humectus (Say) , Copris klugi Harold , Deltochilum mexicanum Burmeister , Dichotomius colonicus (Say) , Onthophagus anthracinus Harold (or near), O. aureofuscus Bates , O. chevrolati retusus Harold , O. mexicanus Bates , O. zapotecus Zunino & Halffter , and Phanaeus damocles Harold.

Chorological affinities. The known collection locality of C. quercetorum is widely separated from that of a similar species, C. delgadoi Kohlmann & Solís , which is distributed in cloud forests on the Pacific slope of the Sierra Madre del Sur from Western Guerrero to Jalisco, Mexico, from 1350–2200 m.

Taxonomic relationships. Canthidium quercetorum is postulated to be the sister species of C. delgadoi . They are both sub-globose in body shape; they also have a swollen frons, narrow eyes, punctate pronotum, shagreen elytra, and shagreen and lightly punctate pygidium.

The two species are very similiar, but C. quercetorum can be easily separated from C. delgadoi using these characteristics: antennal lamellae black (versus pale yellow); pronotum is lightly shagreen; punctures of the elytral striae well defined; aedeagus with a fine, transparent keel running smoothly without forming a step along the dorsal, central midline of the parameres (keel absent in C. delgadoi ); larger than average size (3.9–5.4 mm versus 3.5–4.4 mm); and inhabits a dry oak forest and not a cloud-forest.

Etymology. The name quercetorum is a latin word in genitive plural, meaning “of the oak woods”.

Figures

FIGURE 1.Illustration of the dorsal habitus of a female Canthidium quercetorum new species.

FIGURE 2. Canthidium quercetorum new species. A, the dorsal habitus; B, ventral habitus; C, lateral habitus; D, male protibia; E, female protibia;F, pygidium;and G, aedeagus.

FIGURE 3. Sampling site, A, (grey point) of Canthidium quercetorum new species in Oaxaca (grey area), Mexico (white area). Satelliteimages ofCanthidium quercetorumsampling sites inadeciduous oakforest B,at the dry season (left)andC,at the endof the rainy season (right) (March 2017, November 2014). Bright colours on the left image indicate a forest with trees that have lost their leaves;whereas green vegetationon the same image shows pine-oakforest at higher altitudes,where Canthidium quercetorumhas not been collected.On the right image,oak forest appears withnearly maximum leafdensity at the endof the rainy season.Distributionof D, dry oak forest (dark brown area), situated between approximately 1800 and 2400 m. Sampling site of Canthidium quercetorum is represented by the white rectangle.On the left lower sideof the imagethe urbanarea of the Oaxaca Metropolitan Region can be seen. The dark green area on the right upper side of the image represents pine-oak and pine forest (highest elevation is around 3100 m). Satellite image was provided by GoogleEarth, and oak forest distribution by the Instituto Nacional de Estadística, Geografía e Informática.