Onthophagus mexicanus, Bates, 1887

Kohlmann, Bert & Solís, Ángel, 2025, A review of the species groups of the Western Hemisphere Onthophagus Latreille (Coleoptera: Scarabaeidae: Scarabaeinae) using COI barcoding and gene trees, Zootaxa 5604 (4), pp. 401-447 : 428-429

Onthophagus mexicanus species group.

The males of this group have a slightly emarginate clypeus ( O. mexicanus ), or a small clypeal projection ( O. championi ), or a distinct vertical clypeal horn protrusion present in O. guatemalensis and O. pseudoguatemalensis ( Fig. 5.11 ); slender male protibiae ( Figs. 1.26 –28); apical and internal male protibial margin acuminate ( Figs. 1.26 –28); male protibial apex with some short setae ( Figs. 1.26 –28); male pronotum with a plate-like projection, distally more-or-less distinctly emarginated at middle ( Fig. 5.11 ).

Zunino & Halffter (1988) established this species group based on the Boucomont (1932) “7 e Groupe”. Zunino & Halffter (1997) later defined this group, giving a detailed morphological characterization. Interestingly and opposed to this study, they considered that contrary to groups such as O. clypeatus and O. landolti , this group had a robust internal homogeneity that did not allow for the separation of species groups. Bates (1887) described in the Biologia Centrali-Americana for the first time an O. mexicanus species group comprised of O. championi Bates , O. eulophus Bates , O. guatemalensis Bates , and O. mexicanus Bate s. Moctezuma & Halffter (2021) considered that the group included at least 18 species. We consider the existence of only four species in this group (Appendix 1). The present analysis proposes the idea that at least three new species groups previously considered to form part of the O. mexicanus species group exist within: O. eulophus , O. hecate , and O. velutinus ( Figs. 1–2 ). The present barcode and gene tree analyses ( Figs. 1–2 , 8–9 ) suggest a very close relationship between the O. mexicanus and O. velutinus species groups with a bootstrap support of 93, while the O. hecate species group is distantly related. The O. mexicanus species group is distributed in the mountains from northwestern Mexico to Costa Rica.

Figures

FIG. 5. Onthophagus important characters marked with arrows (details discussed in the text). 1, O. atriglabrus; 2, O. orphnoides; 3, O. propraecellens; 4, O. genuinus; 5, O. andersoni; 6, O. crinitus; 7, O. gazellinus; 8, O. onthochromus; 9. O. landolti; 10, O. anthracinus; 11, O. championi; 12, O. cynomysi; 13, O. orpheus orpheus; 14, O. hoepfneri; 15, O. acuminatus; 16, O. incensus; 17, O. cyanellus; 18, O. sanpabloetlorum; 19, O. cartwrighti; 20, O. velutinus. See Table 7 for the author names of the species listed.

FIG. 1. Neighbor-joining tree for the Western Hemisphere Onthophagus species, based on K2P genetic distances comparisons between COI-5P mitochondrial barcoding sequences. Figs. 23–25 belong to the O. eulophus species group. Figs. 44 and 63 are not assigned to any species group. The male protibiae of the following species are depicted: 1, O. acuminatus; 2, O. batesi; 3, O. incensus; 4, O. nitidor; 5, O. stockwelli; 6, O. striatulus striatulus; 7, O. tristis; 8, O. basicarinatus; 9, O. hircus; 10, O. marginicollis; 11, O. nyctopus; 12, O. onorei; 13, O. osculati; 14, O. ptox; 15, O. ranunculus; 16, O. atriglabrus; 17, O. genuinus; 18, O. rostratus; 19, O. sharpi; 20, O. tapirus; 21, O. villanuevai; 22, O. violetae; 23, O. anewtoni; 24, O. arnetti; 25, O. browni; 26, O. championi; 27, O. guatemalensis; 28, O. mexicanus; 29, O. cartwrighti; 30, O. velutinus; 31, O. alluvius; 32, O. altivagans; 33, O. anthracinus; 34, O. brachypterus; 35, O. chryses; 36, O. landolti; 37, O. lecontei; 38, O. schaefferi; 39, O. concinnus; 40, O. cynomysi; 41, O. hecate hecate; 42, O. medorensis; 43, O. orpheus orpheus; 44, O. polyphemi sparsisetosus; 45, O. chevrolati; 46, O. cyanellus, 47, O. hippopotamus; 48, O. oaxacanus; 49, O. reyesi; 50, O. salvadorensis; 51, O. sanpabloetlorum; 52, O. skelleyi; 53, O. subtropicus; 54, O. totonicapanus; 55, O. vespertilio; 56, O. crinitus; 57, O. gazellinus; 58, O. onthochromus; 59, O. aciculatulus; 60, O. coscineus; 61, O. hoepfneri; 62, O. igualensis; 63, O. lebasi; 64, O. pennsylvanicus; 65, O. subanaeus; 66, tuberculifrons; 67, O. barreti; 68, O.breviconus; 69, O. contrapositus; 70, O. dicranius; 71, O. dorsipilulus; 72, O. humboldti; 73, O. kohlmanni; 74, O. micropterus; 75, O. neomirabilis; 76, O. orphnoides; 77, O. petenensis; 78, O. subcancer; 79, O. andersoni; 80, O. belorhinus; 81, O. grataehelenae; 82, O. limonensis; 83, O. maya; 84, O. praecellens; 85, O. propraecellens; 86, O. rhinolophus; 87, O. rhinophyllus; 88, undescribed species of Onthophagus; 89, O. viridivinosus; 90, O. xanthomerus. See Table 2 for an explanation of the specimen codes. See Table 7 for the author names of the species listed.

FIG. 8. Maximum-likelihood gene tree for the Western Hemisphere Onthophagus species. Bootstrap values were calculated using the rapid bootstrap algorithm of RaxML under the GTRCAT model with 10,000 replicates and run on the CIPRES portal. See Table 2 for an explanation of the specimen codes.

FIG. 9. Maximum-likelihood gene tree for the Western Hemisphere Onthophagus species, partitioned by codon. An IQ-TREE analysis was performed using default parameters for the Invertebrate Mitochondrial Code. See Table 2 for an explanation of the specimen codes.