Axina spina Opitz, 2020

Opitz, Weston, 2020, Taxonomic revision of the Western Hemisphere checkered beetle genus Axina Kirby (Coleoptera: Cleridae: Clerinae), Insecta Mundi 2020 (793), pp. 1-70 : 40-41

Axina spina Opitz , new species

Figures 36 , 73 , 124 .

Type material. Holotype. Male. Type locality: RÉPUBL. ARGENTINE, HAUTE PARANA, TIJU-CUARE PRÈS SAN IGNACIO, E. R. WAGNER ( MNHN) . Paratype. One specimen. Brazil: Estado do Bahia, Encruzilhada,?- XI-1975, M. Alvarenga ( WOPC).

Diagnosis. The members of this species are superficially similar to those of A. basalis , but, in A. spina specimens the midelytral fascia is linear. The fascia is triangular in specimens of A. basalis .

Description. Size. Length 8.0 mm; width 2.0 mm. Form. As in Fig. 124 . Color. Cranium black; antenna testaceous; thorax, legs, and abdomen testaceous; elytra bicolorous, mostly testaceous, humeral angle broadly black, disc with two transverse brown fasciae, one narrow fascia at middle, second fascia broad, in front of elytral apex. Head. Cranium finely punctate, frons slightly wider than length of antennal pedicel; EW/FW 40/15. Thorax. Pronotum finely punctate, with 2 tumescences, concave at middle; PW/PL 80/110; elytra, asetiferous punctures subseriate, punctures extend to elytral ½, interstitial spaces wide; EL/EW 340/60. Abdomen. Aedeagus ( Fig. 36 ), phallobase with spine near lobes; phallobasic lobes very short, nearly contiguous; edges of phallic plates minutely serrate; phallobasic apodeme abbreviated.

Natural history. The paratype was collected in November.

Distribution (for map see Fig. 73 ). This species is known from Brazil.

Etymology. The specific epithet, spina , is a Latin noun with a meaning of “spine”. I refer to the spine on the phallobase.

Evolutionary Considerations

There is comparatively little morphological diversity among the species of Axina , with the obvious result that few characteristics are available for hypothesis of species level evolution. Structures of the antennae, mouthparts, thorax, and legs offer very little information for polarizing character states. The little structural diversity that can be gleaned from adult morphology involves the maxillary palpomeres, characteristics of the elytral disc, visible abdominal sternites, male and female pygidia, and attributes of the aedeagus. Nevertheless, a hypothesis of evolution of the Axina species groups is proposed to serve as a beginning of our understanding of Axina intrageneric relationships. It is hoped that this information will be augmented when additional taxonomically valuable characteristics become available.

Zoogeographic Considerations

I have hypothesized that now there are 51 known species of Axina ; which implies a significant amount of geologic time for the proliferation of species. Therefore, it is puzzling that except for Axina heveli (two specimens from Panama) no other species of Axina apparently traversed the Isthmus of Panama after the closure of the Panamanian portal during the middle Miocene, some 13–15 million years ago ( Montes et al. 2015: 228). Moreover, during this same time interval the Colombian Andes had attained only 40% of their present height (Gregory- Wodzicki 2000: 1303). No northern migrations seem to have taken place during an interval of time when the Colombian Andes were partially formed, some 2.7 million years ago; this despite a considerable window of time for these checkered beetles to enter Middle America considering the formation of the Isthmus of Panama and, at about the same time, establishment of low mountain terrain during the Colombian orogeny.

Most Axina species are found in latitudes proximal to the equator, thus showing an affinity for warm humid forests. Also, there is no evidence that the members of Axina are associated with any particular species of trees. Therefore, it is possible that terrain with cooler climates, generated by rising land masses in northwestern Colombia, may have been an early deterrent for more northern Axina migrations.

Phylogenetic Interpretations

The WINCLADA computer program, in concert with NONA, analyzed 12 apotypic character states and produced one parsimonious tree of a species group phylogeny ( Fig. 68 ). I posit that the Axina ancestor originated in South America, somewhere on the woodland terrains of Brazil, the center of Axina modern species diversity. It is hypothesized that this ancestor (A) diverged to produce ancestral species B and C. Ancestor B generated the progenitor of the bahia species group, characterized by brown elytra, and ancestor C, which evolved the progenitor of the bella species group; in which the elytral asetiferous punctures were reduced in numbers. Ancestor C also produced ancestor D. The latter evolved the ancestor of the basalis species group, which led to species characterized by a female pygidium that is produced at the middle of the posterior margin. Ancestor D promulgated progenitor E, which in one lineage produced the fasciata species group and ancestor F in another lineage. Progenitor F generated the ancestor of the analis species group whose species developed a trilobed condition of the female pygidium. Ancestor F also generated progenitor G which in one lineage produced the analis species group and the fortipes species group in another lineage. These conjectures of relationships are based on few characters. Perhaps the phylogenetic tree will become more comprehensive in character state containment when additional new species taxa are collected and made available.

Figures

Figure 68. Phylogenetic hypothesis (prepared via WINCLADA/NONA).

Figure 73. Distribution map for Axina species: A. chiasta, A. piperata, A. acutipennis, A. spina.

Figures 33–36. Aedeagi. 33) Axina polycaula. 34) A. ochra. 35) A. rio. 36) A. spina.

Figures 122–124. Habitus of Axina species. 122) Axina megaspina. 123) A. sexmaculata. 124) A. spina.