Ateralphus Restello, Iannuzzi & Marinoni, 2001 is a Neotropical genus of longhorn beetles composed of nine species. This genus was proposed from splitting Alphus White, 1855 into other two genera: Ateralphus and Exalphus Restello, Iannuzzi & Marinoni, 2001. Even though Ateralphus (nine species), Alphus (four) and Exalphus (18) were recently revised, their validity has not been tested using phylogenetic methods. In this study, we carried out a cladistic analysis of Ateralphus and its related genera, Alphus and Exalphus, based on 44 morphological characters of the adults, to test their monophyly and infer the relationships between their species. Our results support the monophyly of the three genera and recovered two clades that corroborate the species-groups previously recognized in Ateralphus. A new genus, Grandateralphus gen. n., is proposed for one of these clades, which is supported by three synapomorphies: width of upper ocular lobes less than width between the lobe and the coronal suture (character state 6: 0), genae parallel in frontal view (8: 1) and scape gradually expanded toward apex, reaching widest diameter just near apex (9: 2). Grandateralphus gen. n. includes three new combinations: G. lacteus (Galileo & Martins, 2006), comb. n.; G. tumidus (Souza & Monné, 2013), comb. n.; and G. variegatus (Mendes, 1938), comb. n. Notes on the distribution of G. variegatus comb. n. and a new record of E. cicatricornis Schmid, 2014 for Bolivia (Santa Cruz) are provided.

Acanthoderini , cladistics, distribution, new combination, taxonomy

Ateralphus Restello, Iannuzzi & Marinoni, 2001 is a Neotropical genus of longhorn beetles belonging to Acanthoderini, a tribe of Lamiinae described by Thomson (1860). The tribe Acanthoderini includes 553 species classified into 67 genera, according to Tavakilian and Chevillotte (2016), and is characterized mainly by the piriform scape, shorter than antennomere III, and by the spines or lateral tubercles of the prothorax. Originally, Ateralphus species were classified in Alphus, a genus described by White (1855) for five species, including Alphus subsellatus White, 1855 (subsequently designated as type-species of Ateralphus by Restello et al. (2001)). Restello et al. (2001) proposed two additional genera for species previously included in Alphus White, 1855: Ateralphus and Exalphus; and summarized, in a table, the main characteristics to differentiate the three genera from one another. As part of that contribution, 15 species were included in Exalphus (13 new combinations and two new species), six new combinations were proposed for Ateralphus, and only three species were kept in Alphus.

All species of Alphus and Ateralphus are distributed in South America. Most of them occur in dense forests, such as the Atlantic and the Amazon forests. There are only a few records from open biomes such as the Cerrado and Chaco for Ateralphus subsellatus (White, 1855) and Ateralphus dejeani (Lane, 1973). Exalphus, in contrast, has a broader distribution, from Guatemala to south of South America, with only one species occurring in Central America (Exalphus cavifrons (Bates, 1872)).

Recently, Alphus (four species) and Exalphus (18) were studied by Souza and Monné (2013a) and Souza and Monné (2014), respectively, who updated the distribution data and provided an identification key for their species. After Souza and Monné (2014), two new species were described in Exalphus: E. docquini Tavakilian & Néouze, 2013 and E. cicatricornis Schmid, 2014. Ateralphus (nine species) was revised by Souza and Monné (2013b). They recognized two groups of species in the genus, but failed to name them. In the first group, characterized mainly by the upper ocular lobes separated by three or more times their width, lower ocular lobes narrow and rectangular-shaped, genae parallel to divergent and tibiae with one ring or spot of dark brown setae on sub-apical region, they included A. lacteus Galileo & Martins, 2006, A. tumidus Souza & Monné, 2013 and A. variegatus (Mendes, 1938). In the second group, characterized by the upper ocular lobes separated by less than or equal to twice their width, lower ocular lobes large and rounded, genae convergent and tibiae with dense ring of dark brown setae on apical region, they included the other species of the genus.

In Cerambycidae, new taxa are frequently proposed based only on descriptive taxonomy. In this contribution, we evaluate whether the split of Ateralphus and Exalphus from Alphus, proposed by Restello et al. (2001), can be corroborated through cladistic methods. Our specific goals are: (1) to test the monophyly of Ateralphus and its related genera (Alphus and Exalphus) through phylogenetic analysis based on morphological characters; and (2) to evaluate whether the species groups mentioned by Souza and Monné (2013b) for Ateralphus may be corroborated and formalized as autonomous genera. Additionally, notes on the taxonomy and distribution of some species are provided.

The cladistic analysis resulted in two most parsimonious cladograms (L = 111, CI = 55 and RI = 86). The cladogram selected (showing unambiguous characters only) to represent the relationships among the taxa is presented in Fig. 16 and a summarized tree with the character states optimized under ACCTRAN optimization is presented in Fig. 17. The monophyly of Ateralphus, Alphus and Exalphus were corroborated in our analysis, with strong branch support values, supporting Restello et al.’s (2001) hypotheses.

The monophyly of Alphus was strongly supported in our results by four unambiguous synapomorphies. Three of them are non-homoplastic (Fig. 16), as follows: prothorax with distinct stains of denser setae near the lateral tubercle (character 15: 2); absence of glabrous tubercle or elevation at midline of the pronotum (17: 0); and punctures on basal third of the elytra arranged in longitudinal rows (26: 1; Fig. 15). In addition, one homoplastic character also supports this group: the globose region of the femora, mainly covered with sparse white setae, with denser areas forming irregular maculae (32: 1). This state is also present in some apical lineages of Exalphus, including E. calvifrons, E. cicatricornis, E. gounellei, E. guaraniticus, E. leuconotus, E. lichenophorus and E. malleri. Additionally, one ambiguous, non-homoplastic synapomorphy also corroborates the monophyly of Alphus under fast optimization (Fig. 17): basal apophysis with a diagonal line more sclerotized near apex (44: 1).

Figures 13–15. 

Punctures on basal third of the elytra (character 20) observed among the species included in the cladistic analysis. 13–14, Punctures irregularly distributed, represented by Ateralphus subsellatus and Exalphus leuconotus, respectively; 15, punctures arranged in longitudinal rows, represented by Alphus tuberosus.

Figure 16. 

Tree obtained from the cladistics analysis of Ateralphus and related genera, Alphus and Exalphus. Only unambiguous transformations are shown. A and B show the differences between the two most parsimonious topologies. Bootstrap (gray box) and Bremer support (white box) are indicated below each node. Clades are illustrated by the following species: Alphus similis Martins, 1985; Grandateralphus variegatus comb. n.; Ateralphus subsellatus; and Exalphus leuconotus.

Figure 17. 

Summarized topology obtained from the cladistics analysis of Ateralphus and related genera Alphus and Exalphus, showing all character state transformations under ACCTRAN optimization. CLADE 1: Grandateralphus gen. n.; CLADE 2: Current Ateralphus.

Exalphus is monophyletic, supported by the following unambiguous synapomorphies (Figs 16, 17): posterior margin of head triangular (1: 1; Fig. 1); presence of coarse punctation between upper ocular lobes (4: 1); prothorax with denser line of white setae at median region (15: 1); males with sexual setae on ventral surface of the meso- and metasternum (24: 1); globose region of femora mainly covered with sparse white setae, with denser areas forming transverse bands (32: 2); meso- and metatibiae with stain of dark brown setae on basal half (35:1); tarsomere V bicolored, with dark brown setae at base and basal third (37: 1); tarsomere V bicolored, with dark brown setae at base and apical third (38: 1); ventral lobe larger than dorsal lobe (42: 2). The character states 24: 1, 32: 2, 37:1 and 38: 1 were first mentioned by Restello et al. (2001) to diagnose Exalphus and are confirmed here as synapomorphies for the genus.

Finally, the monophyly of Ateralphus was corroborated by three unambiguous, homoplastic synapomorphies (Fig. 16): coronal suture reaching posterior margin of head (2: 1; Fig. 1B); region between basal-crests covered with dark brown setae (28: 1); and tarsomere V with dark brown setae on apical third (38: 1). Additionally, the following three synapomorphies also support the monophyly of Ateralphus under fast optimization (Fig. 17): antennomere III subequal to antennomere IV in length (11: 1); pronotum straight near the anterior margin (16: 0); and sternite V with longitudinal sulcus at basal region of the females (40: 1).

Two main clades were obtained in Ateralphus, corroborating the species-groups recognized by Souza and Monné (2013b). Clade 1, which includes A. lacteus, A. tumidus and A. variegatus, was supported by the following homoplastic synapomorphies: width of upper ocular lobes less than width between the lobe and the coronal suture (6: 0); genae parallel in frontal view (8: 1; Fig. 8); and scape gradually expanded toward apex, reaching widest diameter just near apex (9: 2; Fig. 12). Clade 2 includes A. auritarsus Souza & Monné, 2013, A. dejeani, A. javariensis (Lane, 1965), A. lucianeae Souza & Monné, 2013, A. senilis Bates, 1862 and A. subsellatus. This clade was supported by the following character states: post-lateral to median tubercles on the pronotum distinctly raised, appearing as a pair of tubercles (18: 2) and color pattern of the lateral margin of the elytra similar to the rest of the elytra. (30: 1). An additional synapomorphy was obtained under fast optimization for clades 1 and 2, respectively: parameres with setae on apex and inner margin (43: 1); and presence of dark brown setae at apical third (36: 1).

Among the genera studied, Alphus may be easily recognized by the punctures on the elytra. Restello et al. (2001) cited the arrangement of the punctures on the elytra as one of the most remarkable characteristics that enable the differentiation of Alphus from Ateralphus and Exalphus. In Alphus, the elytral punctation is present only on the basal half, arranged in longitudinal rows (Fig. 15), a autapomorphy of the genus in our results. By contrast, in Ateralphus and Exalphus the elytral punctation is irregularly distributed on the elytra (character 26; Figs 13, 14).

Although the monophyly of Ateralphus has been corroborated in this study, we consider that clades 1 and 2 are robust enough (synapomorphic characters, bootstrap and Bremer supports; Fig. 16) to be treated as independent genera. Most character states supporting clade 1 are homoplastic (6: 0; 8: 1 and 9: 2), since they are also observed in Acanthoderes albitarsis and in several lineages of Exalphus. However, we consider that these character states are important enough to establish the separation of clade 1 from the remaining species of Ateralphus. Particularly, we highlight the relevance of characters 6 and 8, which were first used by Souza and Monné (2013b) as key characters to differentiate between the two species groups of Ateralphus.

Under ACCTRAN optimization, character state 6: 0 appeared as a plesiomorphic condition, being interpreted here as a reversion in clade 1 (Fig. 17). The transformations of character 8 resulted in a homoplastic synapomorphy for clade 1, with all states widely distributed throughout the topology. The ancestral condition of this character is represented by character state 8: 0 (genae divergent toward apex), whereas character state 8: 1 is an apomorphic condition that appeared independently in several lineages of Exalphus and in the representatives of clade 1. As with character 8, character state 9: 2 can also be interpreted as a case of parallelism or convergence since it has two independent origins in our chosen topology. It is a synapomorphy for clade 1 and for the most apical clade of Exalphus, which includes E. lichenophorus, E. malleri, E. cicatricornis and E. calvifrons (Fig. 16).

In addition to those synapomorphies mentioned above, other characteristics also mentioned by Souza and Monné (2013b) (e.g., shape of the lower ocular lobe, length of antennae and length of the sternite V relative to sternites II, III and IV), are taxonomically important to separate the species of clade 1 from other Ateralphus. Thus, considering the taxonomic significance of the characters supporting the clades 1 and 2, we propose splitting Ateralphus in two genera: Ateralphus (represented by the clade 2), with six species (A. subsellatus (type-species of Ateralphus), A. auritarsus, A. javariensis, A. senilis, A. lucianeae and A. dejeani); and Grandateralphus gen. n., allocating the species previously grouped in clade 1 (A. tumidus, A. lacteus and A. variegatus). All systematic changes proposed in this study are summarized in the ‘TAXONOMY’ section below.

Although the monophyly of Ateralphus, Alphus and Exalphus is strongly supported in our analysis, the phylogenetic relationships between them are not well resolved. A single intergeneric clade with bootstrap over 50% (i.e., Nesozineus alphoides + Alphus) was recovered. It is supported by the following synapomorphies: absence of stain of dark brown setae at apex of antennomeres III to XI (14: 0); mesosternal process slightly convex (22: 0); and, additionally under fast optimization, absence of a stain of dark brown setae on apex of meso- and metatibiae (36: 0).

Despite the low support values, the distribution of the characters on the topology strongly suggests that Ateralphus is the sister group of the lineage (Cotyzineus bruchi + ((Nesozineus alphoides + Alphus) + (Exalphus)). Supporting this relationship are the following synapomorphies: posterior margin of head triangular (1: 0; Fig. 1B); presence of a row of erect setae reaching basal half of antennal tubercles (5: 1); genae convergent in frontal view (8: 2); mesosternal process 45° angulated at apical third relative to mesosternum (23: 1); and absence of a stain of dark brown setae on half basal region of the meso- and metatibiae (35: 0)). Myoxinus pictus has many morphological resemblances with the representatives of Exalphus (which is also expressed by the high number of homoplastic characters exclusively shared between M. pictus and the Exalphus species, i.e., 13: 1; 15: 1; 27: 1 and 29: 1). However, these genera were not recovered as sister groups. Instead, M. pictus resulted as a basal lineage (resulting as sister group of all other species included in the analysis), while Exalphus was corroborated as sister group of (Nesozineus alphoides + Alphus), supported by two synapomorphies: lower ocular lobe larger than gena (7: 2); and absence of elevation post-lateral to the median tubercles of the pronotum (19: 1).

After the description of Alphus, Ateralphus and Exalphus by Restello et al. (2001), no other study has treated the relationships among them or between other genera of Acanthoderini. One exception is the discussion of some characters of these genera by Souza and Monné (2013b). Bates (1862) thought that Alphus (which at that date also comprised species currently placed in Ateralphus and Exalphus) was close to Myoxinus, comparing and differentiating them from Acanthoderes by the shape of the scape, width of the head (measured through the vertex) and shape of the malar area. In our analysis, such characteristics were adapted and codded in characters 9, 6 and 8, respectively.

Except for Acanthoderes, all other species included in our analysis have scape not piriform, slightly shorter than antennomere III (characteristic atypical among the representatives of Acanthoderini). Based mainly on that character, Bates (1862) suggested that Alphus was the lineage link between the tribes Acanthoderini and Acanthocinini, the length of the scape being the key character that keeps it within the Acanthoderini, since in Acanthocinini the length of the scape exceeds that of antennomere III. Apart from the shape of the scape, Bates (1862) also pointed out other characteristics that highlight Alphus among the Acanthoderini, such as mesosternum narrower toward anterior region, base of coxa angled outward and anterior tarsi of males not dilated.

Considering the insights mentioned by Bates (1862) on the evolution of Acanthoderini and the great number of homoplastic characters in our results due to the morphological plasticity observed among the representatives of the subfamily, we suggest that a more comprehensive phylogenetic study including more representatives of Acanthoderini should be conducted, not only to further explore the relationship between these genera, but also to understand the relationships among the genera of Acanthoderini and to evaluate their tribal classification.

We are grateful to James E. Wappes for the loan of specimens for examination; to Tatiana A. Sepúlveda Villa for the valuable considerations to the manuscript; and to Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES) for the first author’s, PhD scholarship. LM and MLM are fellows of the Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq) under the following process numbers, respectively: 307732/2015-0 and 304718/2014-9.