Onthophagus chevrolati, Harold, 1869

Onthophagus chevrolati View in CoL species group.

This group is diagnosed by the male having no clypeal horn ( Figs. 5.17 View FIG –18); male clypeus transverse, with clypeal keel reduced or absent and long frontal keel; female clypeus less transverse with strong and forward-arched clypeal keel; male protibia apex having short setae ( Figs. 1.45 View FIG –55), male pronotum unarmed forming a large gibbosity ( Figs. 5.17 View FIG –18), and well-developed males presenting small head horns ( Figs. 5.17 View FIG –18). Zunino & Halffter (1988: 23) characterized this species group based on the male and female genitalia.

Zunino & Halffter (1988) established the O. chevrolati species group by joining the Boucomont (1932) “1 er Groupe” and “9 e Groupe” and based on proposals and species relationships previously suggested by Boucomont (1932), Howden et al. (1956), Howden & Cartwright (1963), and ( Howden (1973). Palestrini & Zunino (1986) considered this group a vicariant from elements distributed at present in the Chinese Transition Zone ( Stegmann 1930; Müller 1977; Palestrini et al. 1985). The O. chevrolati species group was later subdivided into several species lines and complexes by Halffter et al. (2019). It comprises 59 species (Appendix 1), of which four are included in this analysis, representing the most speciose Western Hemispheric group. It is noteworthy how this group has undergone rapid speciation, primarily associated with the Mexican mountains.

Our mtDNA barcode analysis has recovered the O. chevrolati species group ( Figs. 1–2 View FIG View FIG ). Halffter et al. (2019) proposed the O. cyanellus species complex within this species group, which is recovered in our barcode tree ( Figs. 1–2 View FIG View FIG ). The existence of the O. cyanellus species complex is supported by the unique long and slender metafemur present in O. cyanellus Bates ( Fig. 1.46 View FIG ). Although the present analysis is not all-encompassing, the tree recovers the existence of three of the 10 species complexes proposed by Halffter et al. (2019); the O. brevifrons species complex ( O. brevifrons Horn and O. subtropicus Howden & Cartwright ), the O. chevrolati species complex ( O. cochisus Brown ), and the O. cyanellus species complex ( O. cyanellus Bates ). In their phylogenetic analysis, Emlen et al. (2005) recovered the O. chevrolati species group represented by O. cochisus . This species group is also strongly supported by the other gene trees presented in this study, where the bootstrap study ( Fig. 8 View FIG ) registers a bootstrap value of 91. A more comprehensive analysis might later recover more species complexes. All cave-dwelling and nest-dwelling species have a strongly bent male protibial apical spur; all other species have the typical straight apical spur ( Figs. 1.45 View FIG –55). The O. chevrolati species group is distributed from southern United States of America to Panama.