Gromphas inermis Harold 1869
Creators: name: Cupello, Mario
name: Vaz-de-Mello, Fernando Z.
Publisher: name: Zenodo
Year: 2015
Subjects: Biodiversity
Taxonomy
Animalia
Arthropoda
Insecta
Coleoptera
Scarabaeidae
Gromphas
Gromphas inermis

description: Gromphas inermis Harold, 1869
(Figures 5, 6, 8A)
New geographical records
BOLIVIA: Tarija: Gran Chaco (Yacuiba). PARAGUAY: Paraguarí: Sapucaí. ARGENTINA: Jujuy. Tucumán. Córdoba: Leones. Santa Fe: General Obligado (Villa Ana), Rosario, Santa Fe. Misiones: San Ignacio, Puerto Iguazú. Corrientes: San Roque. Entre Ríos: Villa Paranacito. Buenos Aires: Isla Martín García, Pergamino, San Pedro. Mendoza. URUGUAY: Colonia: Riachuelo. Canelones: Atlántida.
Comments
In Cupello and Vaz-de-Mello (2013), we cited the occurrence of G. inermis in the Bolivian department of Beni based on the report of this species (cited as ‘ G. lacordairei Brullé ’) by Hamel-Leigue et al. (2009). Nonetheless, we know now that the specimens examined by them from Beni are, in fact, G. jardim, and so Beni and the biogeographic province of Rondônia (former Pantanal province, as cited in Cupello and Vaz-de-Mello 2013) should be disregarded as an area of occurrence of G. inermis. On the other hand, localities of the Chacoan province in the departments of Tarija and Santa Cruz, also cited by Hamel- Leigue et al. (2009), are indeed places where G. inermis is present. The occurrence of this species in the Argentine province of Mendoza, as first reported here, is the most western record known for G. inermis (Figure 5).
During our examination of specimens for the revision of Gromphas, we found a female from Artigas, Uruguay, that is very interesting by being matte black and having the pronotal surface completely irregular; nonetheless, taking into account all the other characteristics, it fits in G. inermis, and so we identified that specimen with this name in Cupello and Vaz-de-Mello (2013). Since then, we examined the Hermann Burmeister collection, housed in MACN, and there we found two other Uruguayan females (from ‘ Banda Orient. ’) with a very similar colour and irregular pronotum that were identified by Burmeister with the unavailable name ‘ Gromphas rugicollis Nob. ’. For now, we consider these differences as intraspecific variations of G. inermis (possibly teratological specimens); we observed black specimens of G. inermis from other regions and, in fact, black and brown colorations seems to be related to teneral specimens, which would also explain the irregular surface of pronotum. All the other Uruguayan specimens examined by us are typical G. inermis.
Additional material examined
ARGENTINA: 1904, O. W. Thomas col. – 1 male and 1 female (BMNH); Río Bermejo, without date, H. Richter col. – 1 male and 1 female (MLPA); Río Salado, no more data – 2 males and 2 females (BMNH). BUENOS AIRES: no more data – 2 males (BMNH), 1 female (MACN); without date, H. Richter col. – 2 males and 3 females (MLPA); without date, J. Bosq col. – 1 male and 1 female (MLPA); October 1898, C. Bruch col. – 1 female (MLPA); 10 September 1903, Carlos Bruch col. – 1 male (MACN – Carlos Bruch coll.); 2 March 1904, A. Zotta col. – 1 male (MACN); without locality, Deceber 1921, without collector – 1 male and 1 female (MACN); without locality and date, J. Boso col. – 1 male and 1 female (MACN); 17 km south of Buenos Aires, 8 January 1980, C. and M. Vardy cols. – 1 female (BMNH); Isla Martín Garcia, April 1937, M. J. Viana col. – 1 male (MACN); La Plata, no more data – 2 males (BMNH) and 1 male (MACN); La Plata, without date, A. R. Bezzi col. – 1 male and 1 female (MLPA); Pergamino, February 1949, without collector – 1 male (MLPA); San Isidro, Martínez, 16 February 1924, M. Sires col. – 1 female (MACN); San Pedro, without date, A. G. Frears – 1 male (MACN). CHACO: no more data – 2 males and 1 female (MACN); December 1895, Carlos Bruch col. – 1 male (MACN – Carlos Bruch coll.). CÓRDOBA: no more data – 1 male (BMNH); without date, H. Richter col. – 1 male and 1 female (MLPA); Leones, 30 January 1946, W.N.P. col. – 1 female (MACN).
CORRIENTES: no more data – 1 male and 2 females (MACN), 1 male (MACN – Carlos Bruch coll.), and 2 males and 5 females (MLPA); San Roque, February 1920, Bosq col. – 1 male (MLPA); Santo Tomé, no more data – 4 males and 6 females (MACN); Santo Tomé, October 1925, without collector – 4 males and 1 female (MACN); Santo Tomé, September 1926, without collector – 1 male (MACN). ENTRE RÍOS: no more data – H. Richter col. – 1 male and 1 female (MLPA); Villa Paranacito, no more data – 1 male (MACN). JUJUY: no more data – 1 male and 1 female (MACN) and 2 males and 1 female (MLPA). MENDOZA: no more data – 1 male and 2 females (BMNH). MISIONES: no more data – 8 males and 3 females (MACN); without date, illegible collector – 1 female (MLPA); without date, C. Bruch col. – 1 female (MLPA); without date, H. Richter col. – 1 male and 1 female (MLPA); Alto Paraná, 1 – 18 December 1933, K. J. Hayward col. – 1 female (BMNH); San Ignacio, 1928 – 1929, Quiroga col. – 2 males (MACN); San Ignacio, 21 October 1929, without collector – 1 male (MLPA); Puerto Iguazu, October 1927, without collector – 1 female (MACN). SALTA: without date, H. Richter col. – 1 male (MLPA). SANTA FÉ: Chaco, without date, H. Richter col. – 7 males and 4 females (MLPA); Estancia La Noria, Rio San Javier, 8 – 20 December 1911, G. E. Bryant col. – 8 males and 9 females (BMNH); General Obligado, Villa Ana, FCSF, November 1924, K. J. Hayward col. – 1 male (BMNH); Rosario, without date, A. Stévenin col. – 1 male (MACN); Santa Fé, no more data – 1 male (MLPA). SANTIAGO DEL ESTERO: Río Salado, without date, Wagner col. – 2 females (MLPA). TUCUMÁN: no more data – 1 male and 1 female (BMNH); without date, H. Richter col. – 3 males and 3 females (MLPA). BOLÍVIA: SANTA CRUZ: Chiquitos, Santiago, 18°20 ʹ 17 ” S, 59°35 ʹ 37 ” W, November 1959, without collector – 1 male (CMNC; examined by photo). TARIJA: Gran Chaco, between Yaguacua-Caiza, 21°50 ʹ 52 ” S, 63º36 ʹ 26 ” W, 620 m, 3 January 2005, Mann, Hamel and Herzog cols. – 3 males and 1 female (BMNH) and 35 males and 43 females (OUMNH); Gran Chaco, Yacuiba, 622 m, 21°54 ʹ 03 ” S, 63°37 ʹ 54 ” W, 3 January 2005, Mann, Hamel and Herzog cols. – 1 female (BMNH). BRAZIL: no more data – 1 female (OUMNH – Hope-Westwood coll.). MATO GROSSO: without date, Koslomosky (?) col. – 3 males (MLPA); Poconé, Rodovia Transpantaneira, 8 February 2015, Mario Cupello col. – 1 male (MNRJ). MATO GROSSO DO SUL: Corumbá, Alto Paraguai, without date, H. Richter col. – 1 male (MLPA). RIO GRANDE DO SUL: no more data – 4 males and 1 female (BMNH); 7 November 1959, C. Biezanko col. – 1 female (BMNH); 20 October 1961, C. Biezanko col. – 1 male (BMNH); January 1995, M. A. Fernando (?) col. – 1 male (MACN); Pelotas, 10 November 1953, C. M. Biezanko col. – 1 female (BMNH). SANTA CATARINA: no more data – 3 females (BMNH); March 1820 – 1 female (OUMNH – Hope-Westwood coll.). PARAGUAY: no more data – 1 male (BMNH) and 1 male (MACN); without date, H. Richter col. – 1 male (MLPA); 1908, F. O. Lucas col. – 1 male and 1 female (MLPA). DISTRITO CAPITAL: Asunción, September 1922 to April 1923, E. G. Kent col. – 1 female (BMNH). GUAIRÁ: Villarrica, without date, H. Richter col. – 1 male and 2 females (MLPA). PARAGUARÍ: Sapucai, 1903, W. Foster col. – 2 females (BMNH). URUGUAY: no more data – 2 females (BMNH), 2 males and 2 females (MACN – Hermann Burmeister coll.). CANELONES: Atlántida, no more data – 1 male (MACN). COLONIA: no more data – 1 male (MACN); Riachuelo, without date, A. Stévenin col. – 1 male (MACN). MONTEVIDEO: no more data – 1 male (BMNH); Carrasco, no more data – 1 female (MACN); Peñarol, 20 December 1929, without collector – 1 female (MLPA); Peñarol, 10 October 1933, without collector – 1 female (MLPA). Ambiguous data: ‘ Fives Lille, Bruch-Waiser ’ – 2 males (MACN – Carlos Bruch coll.); ‘ Parana. Nov. ’ (Argentina or Brazil?) – 1 male (MACN – Hermann Burmeister coll.). Specimens surely mislabeled: COLOMBIA: no more data – 1 female (BMNH – Frey coll.). No data: 1 male (MACN – Carlos Bruch coll.), 1 male and 1 female (MACN – Hermann Burmeister coll.), 1 male and 4 females (OUMNH – Hope- Westwood coll.), and 1 female (OUMNH – Gory coll.).
Phylogenetic analysis
The phylogenetic analysis performed here had three main goals: to test the monophyly of Gromphas, to know the phylogenetic relationship of its species, and, therewith, to raise hypotheses about the transformation of their characters through the evolutionary process. In recent works (Philips et al. 2004; Cupello and Vaz-de- Mello 2013), it was well demonstrated that Gromphas is a member of the tribe Phanaeini and closely related to Oruscatus; together, these two genera form the monophyletic subtribe Gromphadina. The monotypic genus Bolbites Harold, 1868, previously considered to be related to this clade, was transferred to Phanaeina by us (Cupello and Vaz-de-Mello 2013) based primarily on the results of the phylogenetic analysis of Philips et al. (2004; morphological data) and of Ocampo and Hawks (2006; molecular data), besides other published information about the nesting behaviour of these three genera (e.g. Cabrera-Walsh and Gandolfo 1996; Halffter and Edmonds 1982; Sánchez and Genise 2008). In Phanaeina, Bolbites is sister of the lineage comprising the remaining genera of the subtribe (Philips et al. 2004; Ocampo and Hawks 2006). Taking these information into account, we selected as outgroups one of the two species of the undoubtedly monophyletic Oruscatus, Oruscatus davus (Erichson, 1847), and one Phanaeina, Bolbites onitoides Harold, 1868, the latter used to root the tree and selected among the Phanaeina by its close morphological similarity with Gromphadina.
Based on 31 informative morphological characters (see below and Table 1), an exhaustive search (implicit enumeration) was conducted using the program TNT (Goloboff et al. 2008) with Fitch parsimony and equally weighted characters, which resulted in a single tree (Figure 6) of length 46, consistency index 78 and retention index 77, both indices calculated in WinClada (Nixon 1999 – 2002). Supports of clades were calculated in TNT using both Bootstrap and decay index (Bremmer support) values, this last index based on a search of the 88 suboptimal trees with up to 10 steps longer than the optimal tree. The most parsimonious tree was edited in WinClada, where unambiguous characters were plotted. The ambiguous characters, on the other hand, were individually optimized based on scenarios considered more likely by us and discussed throughout the text below.
Character statements
The character statements, i.e. the characters (including locators, variables and variable qualifiers) and their states, were presented following Sereno ’ s (2007) proposals. As a result, 31
informative morphological characters were found by us, of which 26 are binary and five multistate.
Head
1. Clypeus, apical margin, form: straight or only slightly upturned (0); clearly bent upward (1).
2. Clypeus, apical margin, shape: with two lobes (0) (Figure 1F); truncate (1) ({fig. 26}).
3. Clypeus, lateral margin, shape: rounded (0) ({figs 24 – 26}); lobate (1) (Figure 1F).
4. Genae, tegument, sculpture adjacent to eyes: granulose (0) (Figure 1F); smooth (1) ({figs 24, 25}).
5. Cephalic projection, shape: wide carina (0); carina with base wider than apex (1) (Figure 1G); horn flattened anteroposteriorly (2) ({figs 29,30}).
6. Cephalic projection, carina with base wider than apex, apex, shape: truncate (0) ({fig. 33); emarginate (1) (Figure 1G).
Thorax
7. Pronotum, centre, mid-longitudinal line of smooth and glossy tegument: absent (0); present (1).
8. Pronotum, posterior fossae: present (0); absent (1).
9. Pronotum, pronotal prominence: absent (0) (Figures 1, 3, 4); present (1) ({figs 1 – 11}).
10. Pronotum, form: irregular surface with single transverse depression or pair of depressions in its anterior region (0) ({figs 1 – 11}); entirely convex and without any king of depression (1) (Figure 1, 3, 4).
11. Mesepimeron, metepisternum and outer sides of metasternum, pilosity: with long and abundant setae (0) (Figure 7B,C); entirely glabrous (1) (Figure 1B, 7A).
12. Metepisternum, metepisternal tab: present (0) (Figure 7B,C); absent (1) (Figure 7A).
13. Metasternum, sides of anteromedian angle, tegument, sculpture: smooth (0); granulose (1) ({figs 49 – 52}).
14. Metasternum, apex and region in front of anteromedian angle, pilosity: with evident pilosity, short or long (0); entirely glabrous (1).
15. Metasternum, centre, tegument, sculpture: irregular (0); densely punctate (1); with fine and sparse punctation (2).
Protibia
16. Ventral longitudinal carina: ornamented with tubercles and/or teeth in males and simple in female (0) ({figs 20d, 23b}); simple in both sexes (1) ({fig. 22}).
17. Ventral longitudinal carina, ornamentation, form: large tooth and small irregular teeth on the middle (0) (Figure 8C); a single large tooth (1) (Figure 8B); a row of tubercles on the basal half (2) (Figure 8A, {figs 20d, 23b}).
18. Protibial spur (articulated spur), apex, shape: only slightly curved (0) ({fig. 22}); strongly expanded (1) ({fig. 23}).
19. Apical tuft of setae, sexual dimorphism: denser and longer in males than in females (0) ({fig. 23}); with same density and length in both sexes (1) ({fig. 22}).
20. Overall shape, sexual dimorphism: narrower in males than in females (0) ({fig. 23}); very broad in both sexes (1) ({fig. 22}).
21. Inner apical angle, tubercle: absent (0); present (1) ({fig. 23b}).
22. Inner apical angle, tubercle, form: tiny and almost imperceptible (0) ({fig. 23b}); developed into a strong spur clearly visible to the naked eye (1) (Figure 2A,B; {fig. 21b}).
23. Apical protarsomere, apex: tapered and only slightly elongate at apex (0) ({figs 22, 46}); with a long spiniform projection (1) ({fig. 45}).
Elytra
24. Elytral striae, basal fossae: present (0); absent (1).
25. Elytral striae, sculpture: very fine and simple, not carinulate (0); especially those more internal, carinulate from base to at least mid-length of elytra (1) ({figs 37, 38}).
26. Sutural margin, tegument, sculpture: densely punctate (0); with fine and sparse punctation (1).
27. Sutural margin, tegument: sheen and punctation limited to sutural margin (0) ({figs 1 – 11}); in basal third or basal half, sheen and punctuation of sutural margin extend onto first or second interstriae (1) (Figures 1A,E, 4); {figs 13 – 15}).
28. Epipleura, shape: entirely horizontal and narrow or curved only at base (0); strongly curved and wide from base of elytron to metacoxa, remainder length horizontal and narrowed (1).
Abdomen
29. Pygidium, basal margin: complete (0) ({fig. 35}); present, but usually interrupted in the middle by the groove of propygidium (1); absent (2) ({fig. 36}).
Aedeagus
30. Genital capsule, phallobase, ventrobasal margin, shape: entirely (0); with median incision (1) ({figs 53 – 56}).
31. Internal sac, medial sclerite, form: wider and strongly curved (0) ({figs 57 – 58}); wider and only slightly curved (1) ({figs 59 – 60}); very fine and strongly curved (2) ({fig. 61}).
The monophyly of Gromphas
In our analysis, the monophyly of Gromphas was strongly supported by eight uncontroverted synapomorphies: outer sides of pterothorax (mesepisternum, metepisternum and sides of metasternum) entirely glabrous (char. 11 – 1; Figures 1B, 7A), metepisternal tab absent (12-1; Figure 7A), sides of anteromedian angle of metasternum with granulose tegument (13-1); {figs 49 – 52}), centre of metasternum densely punctate (15-1), inner apical angle of male protibiae with a tiny tubercle (21-1; {fig. 23b}), elytral striae without basal fossae (24-1), epipleura strongly curved and wide from base of elytron to metacoxa (28-1), and ventrobasal margin of phallobase with median incision (30-1; {figs 53 – 56}). The high support values (bootstrap 99, decay index 7) also give us great confidence in the monophyly of Gromphas.
Edmonds (1972) and Philips et al. (2004) stated that the metepisternal tab was absent in Gromphas and Oruscatus; the first author considered the presence the metepisternal tab as one of the defining characteristics of the phanaeines when these two genera are excluded. However, as we observed in Cupello and Vaz-de-Mello (2013), the two species of Oruscatus have, in fact, a short tab in their metepisterna covering the margin of the elytral epipleura, which has an evident depression at this point to receive the tab, in the same way as in Phanaeina (Figure 7B). We observed this same short metepisternal tab and the respective epipleural depression in a series of other dung beetle genera, including species of Copris Geoffroy, 1762, Dichotomius Hope, 1838 (Figure 7D), Chalcocopris Burmeister, 1846, Homocopris Burmeister, 1846, Ontherus Erichson, 1847, Canthidium Erichson, 1847, and Isocopris Pereira & Martínez, 1960, in the tribe Coprini, Helictopleurus d ’ Orbigny, 1915, Liatongus Reitter, 1893 and Euoniticellus Janssens, 1953, in Oniticellini, and Bubas Mulsant, 1842, in Onitini; in Eucraniini, the putative sister tribe of Phanaeini (Philips et al. 2004; Tarasov and Génier 2015), we have not seen this structure. Nonetheless, the metepisternal tab seen in Phanaeina is unique among the dung beetles by its great development, being much more curved and longer than in any other group observed by us (Figure 7C). Therefore, we consider that this unique form, rather than its mere presence, is one of the defining synapomorphies of Phanaeina. In its turn, Gromphas is exclusive among the Phanaeini in that it has no trace of a metepisternal tab (Figure 7A). The epipleura, however, has a perceptible vestigial depression at the same point as in Oruscatus and the other Phanaeini, indicating again that a metepisternal tab could have been present in the ancestors of the Gromphas. Edmonds (1972, pp. 814 – 815) hypothesized that the metepisternal tab anchors the elytra, maintaining ‘ close elytral appression along the elytral suture by restricting lateral slippage of the elytra ’. Giving assistance during digging, probably this is the same role that the metepisternal tab has in those other dung beetles, which are fossorial and paracoprid.
The presence of only four protarsomeres, rather than five, is also unique to Gromphas, at least among the Phanaeini. In this tribe, protarsi, if present, are found only in females, but ‘ are always reduced in size and clawless ’ (Edmonds 1972, p. 770). In some groups, protarsi are completely absent. Bolbites and Oruscatus are included in this latter case and, in consequence, it is difficult to say if the condition seen in Gromphas (i.e. protarsi with four tarsomeres) was the ancestral condition of Gromphadina and then Oruscatus took a step further and lost completely the protarsi, or if the condition in the last common ancestor was the five-articulated protarsi and then the reduction occurred in Oruscatus and Gromphas independently. So, in the first case, protarsi with four tarsomeres would be a synapomorphy of Gromphadina, whereas in the latter case it would be a synapomorphy of Gromphas. Given these difficulties in the ambiguity of this character, we chose not to include it in the analysis.
The phylogenetic relationship of the species of Gromphas
The six species of Gromphas are divided into two main clades, one including G. aeruginosa and G. lemoinei (clade A in Figure 6), and other including the topology (G. dichroa (G. inermis (G. amazonica + G. jardim ))) (clade B). The first clade is supported by 10 synapomorphies (four uncontroverted, two controverted by homoplasies, and four ambiguous optimized manually): genae smooth adjacent to the eyes (char. 4 – 1; ambiguous and homoplastic with Oruscatus; {figs 24, 25}), cephalic projection developed as a horn flattened anteroposteriorly (5-2; ambiguous; {figs 29, 30}), centre of pronotum with a mid-longitudinal line of smooth and glossy tegument (7-1), presence of pronotal prominence (9-1; {figs 1 – 11}), ventral carina of protibiae simple in both sexes (16-1; {fig. 22}), protibiae with apical tuft of setae without any sexual dimorphism (19-1), protibiae very broad in both sexes (20-1), elytral striae carinulate (25-1; homoplastic with clade D; {fig. 37}), pygidium without basal margin (29-2; ambiguous and homoplastic with clade C; {fig. 36}), and medial sclerite of internal sac wider and strongly curved (30-0; ambiguous; {figs 57, 58}). The values of support are high (bootstrap 99, decay index 6) and give confidence to our hypothesis that these two species are closely related (Cupello and Vaz-de-Mello 2013).
One of the most interesting features of this clade is the reduced sexual dimorphism. In G. aeruginosa and G. lemoinei, the ventral carina of protibiae is simple in both sexes ({fig. 22}), whereas it is ornamented with tubercles or teeth in Oruscatus (Figure 8B), Bolbites (Figure 8C) and in three of the other four Gromphas (G. jardim is the exception) (Figure 8A). In the other Phanaeina, this carina is also simple in both sexes. Other reductions in sexual dimorphism are the protibiae very broad and the protibial tuft of setae of same length in both sexes. In the other Gromphas (and Oruscatus and Bolbites), males have narrower protibiae and the tuft of setae is much longer and denser in males than in females (Figure 2, {fig. 23}). The presence of a pronotal prominence is also a remarkable characteristic of this clade, being absent in the other Gromphadina; nonetheless, as is typical for these two species, there is no sexual difference in this feature. In Phanaeina, in general, males have very elaborate ornamentation on head and pronotum, and it has been known since Darwin (1859, 1871) that these structures play a key role in the sexual access to females by males and, therefore, are under constant pressure from sexual selection (see, for example, Otronen 1988; Rasmussen 1994; Escobar 2003; Emlen and Philips 2006; Rowland and Emlen 2009). But what would be the reason for these structures being as developed in females as in males in this clade? A few other groups of Phanaeini also have females with ornamentation greatly developed, as in males, including those of the group lancifer of subgenus Megaphanaeus d ’ Olsoufieff, 1924, of Coprophanaeus d ’ Olsoufieff, 1924, and, to a lesser extent, the group faunus of Sulcophanaeus d ’ Olsoufieff, 1924, groups that include some of the largest dung beetles of the New World (Edmonds 2000; Edmonds and Zidek 2010). Otronen (1988) supposed that females of Coprophanaeus (M.) ensifer (Germar, 1821) need a developed armature to face combat against other females and so obtain enough food for their large larvae; larvae of smaller dung beetles, on the other hand, do not need large amounts of food and therefore females of these species do not need to face such fierce disputes. Not having such a large size, females of G. aeruginosa and G. lemoinei are unique in possessing well-developed ornamentation. Only with a greater knowledge of their biology will we be able to answer this question more firmly, but it is possible that some idiosyncrasy in their behaviour leads females to fight battles and so be in need of such armament.
The second main lineage within Gromphas, clade B, is supported by five synapomorphies (three uncontroverted, two ambiguous): cephalic projection as a carina with base wider than apex (char. 5 – 1; ambiguous; {figs 31 – 33}), pronotum globular (10-1), ventral carina of male protibiae with a row of tubercles on basal half (17-2; ambiguous; {fig. 23b}), protibial spur strongly expanded at apex (18-1; {fig. 23}), and, on basal third or basal half, sheen and punctation of sutural margin of elytra extend onto first or second interstriae (27-1; {figs 13 – 15}). The values of support for this clade, however, are the lowest in our analysis (bootstrap 55, decay index 2). One interesting synapomorphy of this lineage is the form of the ornamentation of the ventral carina of male protibiae. In Bolbites, this carina has few tiny, irregular teeth and one large central tooth (Figure 8C); in Oruscatus, this ornamentation is modified into a single central tooth without any accessory teeth or tubercles (Figure 8B). In G. dichroa, G. inermis and G. amazonica, the carina has a row of tiny, regular tubercles, with no apparent difference between these species ({fig. 23b}); in G. jardim, as a controverted autapomorphy (char. 16 – 1, homoplastic with clade A), this ornamentation is lost and the carina is simple and continuous (Figure 2A).
The next clade, clade C, is supported by five synapomorphies (two uncontroverted, three ambiguous): apical margin of clypeus evidently upturned (1-1), lateral margin of clypeus lobate (3-1; Figure 1F), cephalic carina emarginate apically (6-1; ambiguous; Figure 7), pygidium without basal margin (29-1; ambiguous and homoplastic with clade A; {fig. 35}), and medial sclerite of internal sac wider and only slightly curved (31-1; ambiguous) ({figs 59, 60}). The support values give us confidence in this hypothesis (bootstrap 76, decay index 2). This lineage shares with G. aeruginosa and G. lemoinei one important condition, the basal margin of pygidium completely absent ({fig. 36}). Gromphas dichroa, in its turn, possesses the basal margin complete as Bolbites and the other Phanaeina ({fig. 35}). The two species of Oruscatus apparently have an intermediate condition: the basal margin is present, but in the majority of specimens it is interrupted in the middle by the sulcus of propygidium. So, albeit complete in G. dichroa, we believe that there is a general tendency in Gromphadina for the loss of this basal margin, perhaps linked to the great development of the propygidium (which has the length of the pygidium in Gromphadina, and is shorter than the pygidium in Phanaeina), and, therefore, we judge that the most likely scenario was the parallel and independent loss in both lineages rather than a unique loss in the ancestral Gromphas and a new origin in G. dichroa. The form of the medial sclerite of the internal sac of this lineage is very different to that of clade A and G. dichroa and, at same time, homogeneous between its species ({figs 59, 60}). As this sclerite is absent both in Bolbites and Oruscatus, it was not possible to properly polarize this character and, given the topology of the tree, it remained ambiguous in our analysis.
The last clade includes G. amazonica and G. jardim, sharing four apomorphies (two uncontroverted and two controverted): centre of metasternum with sparse punctation (15-2; homoplastic with G. aeruginosa), tubercle of apical inner angle of protibiae modified in a strong spur (22-1; Figure 2, {fig. 21b}), apical protarsomere with spiniform projection at apex (23-1; {fig. 45}), and elytral striae carinulate (25-1; homoplastic with clade G. aeruginosa + G. lemoinei;{fig. 38}). The support values are also robust (bootstrap 78, decay index 3). The most remarkable synapomorphy of this lineage is the protibial tubercle developed into a strong spur, which has no parallel within the genus; the great differences between the two species regarding the form of this spur are discussed in the description of G. jardim above.
Phylogenetic conclusion
Through this phylogenetic analysis, we observed that features related to tegument [e.g. punctation (chars. 17 and 26) or carinulae of elytral striae (char. 25)], which are of a great importance for species identification, were the most error-prone characters for the construction of primary homologies and, so, led to more homoplasies (see Nixon and Carpenter 2012 on homoplasy as error). The differences in pronotal granulation were also very difficult to codify and to include in our analysis because of their gradual variation between species. In fact, there is no pair of species of Gromphas with the same pattern of pronotal granulation. For the same reason, codifying the differences in the form of the anteromedian angle of metasternum was virtually impossible. Nonetheless, in this latter case, there is a clear homogeneity among the forms founded in G. amazonica, G. jardim and G. inermis ({figs 50, 51}), on one side, and in G. aeruginosa and G. lemoinei ({fig. 52}), on the other. The form seen in G. dichroa, which is high, narrow and truncate apically, is unique in the genus ({fig. 49}). Finally, the usual apomorphic absence of posterior pronotal fossae in G. inermis and G. amazonica appeared ambiguous in our analysis, with two possible scenarios: the loss of the fossae in the ancestral of clade C and its subsequent reappearance in G. jardim, or independent losses in G. inermis and G. amazonica. In this case, we have no opinion on which scenario would be more likely and therefore we have not plotted this character on the tree.
We consider that the results of this phylogenetic analysis are important not only because they allows us to reconstruct the evolution of Gromphas, but, on a larger scale, because they represent a further contribution to the understanding of the evolution of the dung beetle fauna of the New World. Other American genera with published cladistic analyses of their species are Ateuchus Weber, 1801 (Kohlman 1984; only North American species), Ontherus Erichson, 1847 (Génier 1996), Bdelyrus Harold, 1869 (Cook 1998, 2000), Cryptocanthon Balthasar, 1942 (Cook 2002), Scatimus Erichson, 1847 and Scatrichus Génier and Kohlmann, 2003 (Génier and Kohlmann 2003), Phanaeus MacLeay, 1819 (Price 2007, 2009) and Zonocopris Arrow, 1932 (Vaz-de-Mello 2007).
description: Published as part of Cupello, Mario & Vaz-de-Mello, Fernando Z., 2015, A new species and the phylogeny of the South American genus Gromphas Brullé, 1837 (Coleoptera: Scarabaeidae: Scarabaeinae: Phanaeini), pp. 943-969 in Journal of Natural History 50 on pages 955-966, DOI: 10.1080/00222933.2015.1091099, http://zenodo.org/record/3990441