Elevating Omophoita octoguttata elytralis Bechyné, 1956 (Coleoptera: Chrysomelidae: Galerucinae: Alticini) to species

Abstract An updated morphological description for Omophoita elytralis (Bechyné, 1956), stat. nov., is presented, including the first account of the genitalia for this species. The separation Omophoita elytralis from O. octoguttata (Fabricius, 1775) is supported by differences found in the median lobe of males, elytral tegument uniform in color (not patterned), and their allopatric geographical distribution.


INTRODUCTION
Neotropical beetles in the subtribe Oedionychina Chapuis 1875 display as their most noticeable feature a great variation in their colorful elytral patterns, the main characteristics separating Oedionychina from related groups being the inflated posterior tarsal segment in combination with confused elytral punctuation (Konstantinov et al., 2022). An example of such dubious utility for elytral patterns is the genus Omophoita Chevrolat, 1836, in which the color patterns have shown to be somewhat constant among some species and useful for delimitations and identification, while varying within populations in other species (Bechyné, 1955).
Omophoita (Chrysomelidae: Galerucinae: Alticini: Oedionychina) is a diverse genus of the Neotropical coleopteran fauna, currently including 89 species, 83 of which are recorded for Brazil (Bechyné, 1955;Bechyné, 1959;Sekerka et al., 2020). Individuals of this genus are often sampled in biodiversity studies (Linzmeier et al., 2006;Rech & Linzmeier, 2019). The main distinctive characters of Omophoita are the pale-yellow macula observed in the vertex, the presence of three or more pairs of irregularly distributed bristles on the labrum, and the first metatarsomere longer than the adjacent tarsomeres (Bechyné, 1955). Most species of Omophoita have yet to be revised, and the existing literature dealing with description usually focus on external characters like coloration, lack illustrations, and only rarely detail the genitalia morphology. However, whenever taxonomic conundrums of similar species are encountered, the specific morphology of genitalia has proven to be reliable on delimiting species (e.g., Konstantinov, 1998;Richmond et al., 2016). This appears to be the case for the species O. octoguttata (Fabricius, 1775), particularly referring to O. octoguttata elytralis Bechyné, 1956, its only subspecies, whose entire taxonomic history consists of a brief initial description note, that does not allow for an unambiguous separation. Omophoita octoguttata elytralis' distribution also does not overlap with O. octoguttata stricto sensu's, with the former being only known in literature from a single publication, i.e., its original description, for the central state of Goiás, in the Brazilian Cerrado (Bechyné, 1956), while the later has a broader distribution from Bahia to Rio Grande do Sul, within moist ombrophilous forests (Begha et al., 2021). Aiming to clarify such taxonomic issues, we present an updated description of the morphology and discuss its delimiting

MATERIAL AND METHODS
The morphological studies of O. elytralis were based on holotype and ten paratypes housed in the Museu de Zoologia da Universidade de São Paulo, São Paulo, Brazil (MZSP). Genitalia were dissected following protocols described by Smith (1979). The dissected structures were preserved in glycerin, stored in a microtube placed alongside the original individuals (which were fixed in ethanol 70% after dissection). Only the tignum, vaginal palpi, spermatheca (for females), and median lobe (for males) were analyzed, as the other components of the genitalia were much less sclerotized and often lost during the dissection process.

RESULTS
A description of internal and external morphology of O. elytralis follows. We believe the morphological details present in O. elytralis are enough to classify it as a separate species of its own, and not as a subpopulation of O. octoguttata.
Head: Rounded, black. Vertex at the same level of tegument, with sparse punctation. Inconspicuous supraorbital suture, smooth integument. Supraorbital pore with long and erect seta. Eight to ten setae at lateral margin of head macula, near eyes. Twelve setae scattered between antennal insertions. Gena with nearly same width as the eye, bearing several setae. Antennae black, filiform, with eleven antennomeres; scape subcylindrical, antennomere II shorter than III, antennomere III-X subequal in length, subconical, longer than antennomere XI, which is also subcylindrical, albeit with a narrower, acute apex; antennal insertions ovoid, smaller than the diameter of the eye, interantennal space approximately same size of antennal insertions. Antennae comparatively longer in males. Frontoclypeus subtrapezoid. Labrum with rounded distal margins, central portion emarginated, with ten long setae disposed horizontally.
Thorax: Pronotum transverse, width twice the length, lateral margins and angles rounded, with a long seta at each angle; anterior angles extending beyond the head insertion; hypomeral lobe inflated, laterally and ventrally distinct; disk lacking any setae or impression, dark orange. Prosternum with the same color as the pronotum; prosternal process relatively narrow, widening apically, rounded at apex. Scutellum black, triangular with rounded posterior vertex; procoxal cavities open. Elytral integument yellow, lacking visible maculae region, edges of the elytral black. Epipleura visible laterally in the humeral region. Mesosternum and metasternum black, surface densely covered with fine pale hairs; metasternum elongated, rectangular; outer margins of the thorax with a higher density of hairs.
Legs: Fore and median legs similar, with coxae subcylindrical, slender femur and tibiae; middle legs slightly longer. Surface densely covered with fine pale hairs, pilosity on the metafemur concentrated in the outer margin. Metafemora thickened due to the internal metafemoral spring; fusiform shape. Tarsi pseudotetramerous, claws appendiculate; metatarsomere V enlarged, fusiform.
Abdomen: Black, with five ventrites densely covered with fine pale hairs: ventrites I-IV subequal in length, pygidium slightly longer than the other ventrites and rounded.
Male genitalia: Median lobe ( Fig. 2A) with apical hood (APH) acuminated. Ventral sclerite (VNS) visible in dorsal view; longer than the sides of the median lobe, apex acuminated. Dorsal median process (DMP) visible; proximal portion of the dorsal median process and apex with subequal width; with two wide divergent projections at the apex (PDM), triangular-shaped. Two lateral dorsal sclerites (LDS) visible, triangular, forming a straight angle. Oblique dorsal process (ODP) ventrally curved.
Female genitalia: Membranous bursa copulatrix. Tignum (Fig. 2B) with base (BPT) three times wider than the apex; hood-like structure (HDL) in the median portion present; median portion opaque; distal portion slender; apical margins divergent. Spermatheca simple, with reniform and well-sclerotized receptacle; spermathecal duct long, curled. Vaginal palpi elongated with sigmoid shape, with a thin base, slightly wider and more sclerotized at the apex, ten setae at the apex.

DISCUSSION
The most noticeable difference between O. octoguttata and O. elytralis is that the latter presents no black markings dividing the yellow coloration of the elytra, thus it does not have distinct maculae. Most specific patterns among Omophoita can be considered and useful for identification. Even in species with intraspecific variations, elytral coloration tends to form a "gradient of patterns" as can be observed with O. sericella in Bechyné (1955). This species is remarkable compared to the other Brazilian Omophoita due to its homogeneously colored elytra that lack any visible macula patterns. (Bechyné, 1956). General structure of the genitalia. (A) General structure of the male median lobe. (B) General structure of the female tignum and vaginal palpus. Abbreviations: apical hood (APH); basal portion of the tignum (BPT); distal portion of the tignum (DPT); dorsal median process (DMP); hood-like structure (HDL); lateral dorsal sclerite (LDS); oblique dorsal process (ODP); projections of the dorsal median process (PDM); ventral sclerite (VNS). Pap. Avulsos Zool., 2023;v.63: e202363016 3/5 Morphological dissimilarity between male and female genitalia was also observed. The most noticeable and easily identifiable differences are in the male median lobe, the apical region is slightly different between O. octoguttata and O. elytralis: the apical hood in O. elytralis is acuminated and narrower at the apex, while O. octoguttata is broader and angulated; the dorsal median process of O. elytralis is broader in the median section; the shape of the dorsal lateral sclerite also differs, while both are triangular, O. elytralis' has a straight angle, and O. octoguttata's points outwards (Fig. 3). As for female genitalia, the tignum of O. octoguttata has a goblet shape with the base a little more than two times the width of the apex (Begha et al., 2021), while the base of the tignum of O. elytralis is much wider, with three times wider than the apex. The spermatheca and vaginal palpi of O. elytralis has identical morphology to that described in Begha et al. (2021, Figs. 14-15) for O. octoguttata. Morphology of the interlocking genitalia is often used to separate species through reproductive incompatibility (Fossen et al., 2016), and relatively small differences must not be overlooked.

Figure 2. Omophoita elytralis
Another information that suggests the separation of species is the allopatric geographic distribution area. While specimens of O. elytralis do not present many records in literature, they have only ever collected in the state of Goiás, deep into the Cerrado biome, while O. octoguttata have shown a much wider distribution, collected in the Atlantic Forest or Mixed Rain Forest, and even when collected in other biomes, these collection sites are not far from a rainforest area. Even though there is enough distinction to separate these beetles into different species, both O. octoguttata and O. elytralis share many morphological traits, such as the patterns of the head maculae, labrum setae and overall genitalia structure (Bechyné, 1956;Begha et al., 2021).
This study highlights how overlooked characteristics on older taxa can reveal new taxonomical insights, and that internal morphology should not be ignored. Based on geographical isolation and morphological differences, we here elevate O. octoguttata elytralis to species level, as O. elytralis. Further studies should be developed on Omophoita, and other close genera lacking detailed taxonomic resolution, especially those with complex elytral patterns prone to misidentification. Our study adds to the scarce knowledge of Oedionychina, in the hopes to better clarify the species delimitations and the true diversity of the neotropical fauna.    (MZUSP), and the curator of Coleoptera Dr. Sônia Casari, for loaning the studied material; UEPG (Universidade Estadual de Ponta Grossa); LabGEv (Laboratório de Genética e Evolução) and PPG-BioEvol (Programa de Pós-Graduação em Biologia Evolutiva) for providing the work infrastructure.