Recognition of species groups of Naupactus Dejean (Coleoptera: Curculionidae) from Argentina and neighboring countries

Naupactus Dejean is the most diverse genus of the tribe Naupactini (Curculionidae: Entiminae), with more than 200 species occurring in South America, of which about 40 range in Argentina and neighboring countries. The Argentinean species treated herein were classified into nine groups having different biogeographic patterns: (1) the groups of Naupactus xanthographus, N. delicatulus and N. auricinctus mainly occur in northeastern Argentina (Misiones province) and reach the highest species diversity in the Atlantic and Parana forests of Brazil; (2) the groups of N. hirtellus, N. cinereidorsum, N. rivulosus and N. tarsalis show the highest species diversity in the Chacoan biogeographic province and also occur in the Yungas, Espinal, Monte, Parana forest (Argentina) and Cerrado (Brazil); (3) the groups of N. leucoloma and N. purpureoviolaceus have the highest species diversity in the Pampean biogeographic province, being also present in adjoining areas, mainly Chaco, Espinal, Monte and Parana forest. We provide descriptions, a dichotomous key, habitus photographs and line drawings of genitalia for the identification of the nine species groups, and a list of the Argentinean species from each group, together with their abbreviated synonymies, updated geographic distributions (including six new country records and several state/province records) and host plant associations. We discuss the characters that allow the separation of the species groups in a geographic distribution context, and provide information on species reassigned to genera other than Naupactus; among these, we transferred N. cephalotes (Hustache) to the tribe Tanymecini, genus Eurymetopellus, establishing the new combination Eurymetopellus cephalotes.


INTRODUCTION
Naupactus Dejean is the most diverse genus of the tribe Naupactini (Curculionidae: Entiminae), with ca. 200 species occurring in South America (Wibmer & O'Brien, 1986;Bordón, 1997) and five in Central America, which were previously classified in Alceis Billberg by O' Brien & Wibmer (1982). However, the precise number is still uncertain because new species remain to be described while others should probably be synonymized (Lanteri & del Río, 2017a).  published the only comprehensive taxonomic work on Naupactus from Argentina and neighboring countries, which included a dichotomous key, descriptions of several species and new geographic records for taxa previously described by Boheman (1833) and Schoenherr (1840) and by himself (Hustache, 1923(Hustache, , 1926(Hustache, , 1938. Nonetheless, these contributions lack illustrations of habitus or external features of taxonomic value, descriptions of genital characters, information on host plant associations and provide limited geographic data. The checklist of Wibmer & O'Brien (1986) included new synonymies proposed by Kuschel and updated country records for several species. They reported 45 Argentinean species, but this number was increased to 57 by Morrone (1999) as a result of transferring most of the South American taxa previously classified in Pantomorus Schoenherr to Naupactus.
The earliest classification of the South American Naupactus into species groups was made by Lanteri & Marvaldi (1995) and Lanteri & del Río (2017a). They described and revised the N. leucoloma Boheman and N. xanthographus (Germar) species groups, which include some species of great economic importance due to the damage they cause to agriculture in Argentina and other countries worldwide (Buchanan, 1939;Elgueta, 1993;Guzmán, Lanteri & Confalonieri, 2012;Lanteri et al., 2013). Moreover, they analyzed the phylogenetic placement of Naupactus within the tribe Naupactini (Lanteri & del Río, 2017b; and proposed new synonymies for some species showing color variation, morphotypes and/or sexual dimorphism .
The main objectives of this paper are to recognize and describe the species groups of Naupactus distributed in Argentina and neighboring countries; to provide a dichotomous key for their identification; to illustrate the diagnostic features of these groups by habitus photographs and line drawings of genitalia; and to provide updated information on the synonymies, host plant associations and geographic distributions for all the Argentinean species included in these groups. The recognition of species groups is very useful to identify species belonging to highly diverse genera and helps to understand their evolution in a historical biogeographic context (del Río, Morrone & Lanteri, 2015;.

MATERIALS AND METHODS
This study is based on the examination of about 5,000 specimens deposited in the following entomological collections: American Museum of Natural History 5. Integument slightly sclerotized, covered with iridescent green, purple or copper colored scales; elytral setae usually long and erect. Antennae slender, usually reddish; scape reaching to slightly exceeding hind margin of eye. Pronotum subcylindrical, punctuate or rugose, usually very convex in males. Disc of elytra flat to slightly convex, lower than pronotum in lateral view.  (2018). This species number is the result of the following taxonomic and nomenclatural decisions: 1. Lanteri & Marvaldi (1995) synonymized Graphognathus Buchanan with Naupactus, and consequently the three species of "white-fringed beetles" assigned to Graphognathus in Wibmer & O'Brien (1986) were named N. leucoloma Boheman, N. minor (Buchanan) and N. peregrinus (Buchanan).
Male genitalia: apex of median lobe subacute with small prominence at the tip (Fig. 7A), slightly recurved; apodemes about as long as, to slightly shorter than median lobe (see Fig. 7F). Endophallus without sclerites.

Species included:
12-Naupactus delicatulus   Description. Species medium-sized to large (females 9-17 mm; males 8.5-12 mm) (Figs. 1H and 1I). Integument slightly sclerotized; antennae, tibiae and meso and metafemora often reddish. Scaly vestiture usually iridescent green, pinkish, copper-colored or grayish, in some species with lighter stripes along sides of pronotum and elytra; scales round, slightly overlapped; elytral setae fine, dark, erect, medium to very long. Rostrum directed forward, 1-1.30X as long as wide at apex; lateral carinae subparallel, usually sharp. Forehead 1.25-1.45X as long as rostrum at apex. Eyes usually convex. Antennae very slender, long; scape clavate to slightly capitate, usually exceeding hind margin of eye (except in N. versatilis); funicular article 2, 2.3-3.4X as long as article 1; remaining articles 3.35-4.7X as long as wide; club 3-3.5X as long as wide. Pronotum subcylindrical, often with remarkable sexual dimorphism, 1.20-1.35X as wide as long in females, 1.05-1.20X in males; disc slightly convex in females and strongly convex in males of some species, granulose to strigose; base usually straight, not beveled. Scutellum setose. Elytra 1.6-1.8X as long as wide, disc slightly higher than pronotum (females) or completely flat (males); humeri broad to slightly reduced; base straight to slightly bisinuate, not beveled; intervals flat, often with transversal rugosities; punctures small to indistinct; subapicall calli indistinct. Metathoracic wings well-developed. Procoxae often with denticles in males; profemora much wider than metafemora in males or some Brazilian species (N. condecoratus, N. bipes, N. pithecius); protibiae often inwardly curved, with large mucro and row of usually small denticles on inner margin; meso and metatibiae lacking mucro in females, and with small mucro in males. Metatibial apex without corbels; dorsal comb about as long as distal comb.
Male genitalia: apex of median lobe subacute, curved, with small prominence at the tip (see Fig. 7A); apodemes about as long as, to slightly longer than median lobe. Endophallus without sclerites.
Male genitalia: apex of median lobe acute to subacute, with small prominence at the tip (see Fig. 7A); apodemes about as long as median lobe. Endophallus without sclerites.

Species included:
22-Naupactus argentatus  Geographic distribution. Argentina (Corrientes, Misiones, Santa Fe and Santiago del Estero) and Paraguay (Presidente Hayes). Paraguay is a new country record.
Naupactus leucoloma species group (Fig. 3C) It was revised by Lanteri & Marvaldi (1995) and includes five species mainly distributed in the Pampean biogeographic province and nearby areas (Chaco, Yungas, Espinal and borders of the Paraná forest). N. leucoloma Boheman shows the broadest distribution (Guzmán, Lanteri & Confalonieri, 2012), being introduced in Chile (including Eastern Island and Juan Fernández Islands) and other countries worldwide. N. minor (Buchanan) and N. peregrinus (Buchanan) are typical Pampean species and were also introduced outside their native range. N. albolateralis Hustache is endemic to Argentina (Chacoan biogeographic province) and N. tucumanensis Hustache ranges also in Bolivia (Yungas) and Paraguay (Chaco).
Male genitalia: apex of median lobe usually subacute with small prominence at the tip (see Fig. 7A) (with broad prominence in N. dives); apodemes slightly shorter to about half length of median lobe (Fig. 7F). Endophallus without sclerites or with small U-shaped sclerites. Parana forest and Cerrado in Brazil). The N. leucoloma and N. purpureoviolaceus species groups are mainly distributed in the Pampean biogeographic province, and also occur in nearby areas, for example, Chaco, Espinal and Monte. Some species of these groups reach the southernmost distribution limit of the genus Naupactus in the Americas, and exhibit morphological characters typical of treeless and/or xerophilous environments, for example, reduction of hind wings, a strongly sclerotized integument almost denuded of scales, presence of long erect setae on the elytra, and presence of rows of denticles along the inner edge of all tibiae. In all Naupactus groups, the most differentiated species occur at the edges of their geographic distributions, where the environmental conditions are usually more extreme e.g. N. rugosus in the Monte biogeographic province; N. suphurifer mainly in Monte and Espinal, and N. dives in Espinal and arid areas of the Pampean biogeographic province. Some species groups are more homogeneous than others in terms of external morphology and/or characters of genitalia. The species included in the group of N. rivulosus (type species of Naupactus) share quite uniform ovipositors and spermathecae, for example, ovipositor about 2/3 as long as the abdomen, with rows of setae along the posterior half and well-developed styli (del Río et al., 2018) (Fig. 5A), and spermatheca with strongly sclerotized walls, a very short collum (duct lobe) and a slightly developed ramus (gland lobe) (Fig. 6A). The sternite VIII varies in shape, being oval with or without apical prominence, or subrhomboidal as in most Naupactini (Lanteri & del Río, 2017b) (see Figs. 4A, 4B and 4F), and usually bears a long apodeme. N. sulphurifer (Fig. 1E) has a female terminalia typical of the N. rivulosus species group but differs in some characters of external morphology, for example, a subcylindrical and slightly granulose pronotum instead of a subconical and smooth pronotum as in most species of the group, slightly longer antennae than those of the remaining species, and all tibiae having rows of denticles on the inner edge, at least in males.
Naupactus cyphoides is the most different within the N. tarsalis species group (Fig. 2C), showing shorter antennae than the remaining species (the funicle article 2 is less than two times as long as the funicle article 1 and the funicle articles 3-7 are less than two times as long as wide at apex); a pronotum more than 1.50 times as wide as long; a metatibial apex with a very slender corbel; and a broader spermatheca without thickened walls (Fig. 7E). The spermatheca of the single Argentinean species of the N. delicatulus species group does not show the typical generic characters, for example, it has a subcylindrical and very long collum, a well-developed ramus (see Fig. 6D) and a broad and curled spermathecal duct resembling that of the species of Cyrtomon Schoenherr (Lanteri & del Río, 2016). A spermatheca of similar shape is observed in N. dissimulator and N. marvaldiae, both belonging to the same subgroup within the N. xanthographus species group.
The N. auricinctus species group is quite homogeneous in terms of external morphology and genitalia and differs from the other groups by the presence of a spiraled spermathecal duct (Fig. 6B). Based on a phylogenetic analysis by del , this species group may be related to the N. purpureoviolaceus species group, which is characterized by having a usually undulate spermathecal duct (Fig. 6C). Two species of the latter group exhibit ovipositor characters that differ from those of most Naupactus. In N. dives, the ovipositor is distinguished by lacking long setae on its posterior half, by having more sclerotized coxites as compared to the remaining species and by lacking styli (Fig. 5D); while N. rugosus has a short and wide ovipositor without the typical rows of long setae (Fig. 5E). The ovipositor of N. dives resembles that of Floresianus Hustache, Eurymetopus Schoenherr and Priocyphus Hustache, all of which seem to be adapted for laying eggs into the soil (Lanteri & del Río, 2008); and the ovipositor of N. rugosus resembles that of Trichonaupactus densior Hustache, both of which inhabit similar environments (Lanteri & del Río, 2008, 2016. The sternite VIII of N. rugosus looks like that of some species within the N. rivulosus species group (e.g., N. bruchi), but it has a shorter apodeme (Fig. 4F). Moreover, in N. rugosus the integument is more strongly sclerotized, the scaly vestiture is almost lacking, the pronotum is more rugose and all the tibiae have rows of denticles on the inner edge, particularly in males. Likewise, other Naupactini from environments that are also dominated by xerophilous trees and thorny shrubs (i.e., Enoplopactus Heller, Priocyphopsis Hustache, Mendozella Hustache) have denticles on all tibiae and often display tubercles on pronotum and elytra (Lanteri, 1990;Lanteri & del Río, 2016).
The morphology of the male genitalia provides few useful characters for the differentiation of species groups of Naupactus. In most species, the apex of the median lobe is subacute and ends in a narrow or broad prominence (Figs. 7E-7F). In the N. leucoloma and N. purpureoviolaceus species groups, this prominence may be indistinct and the apodemes are usually much shorter than the median lobe (Fig. 7F), whereas in most of the remaining groups the latter are usually about as long as the median lobe (Fig. 7E). The arrow-shaped (Fig. 7D) or subtriangular (Fig. 7B) apex, recorded for some members of the N. xanthographus species group (N. xanthographus, N. dissimilis and N. mimicus) and N. delicatulus, respectively, are not typical of Naupactus. In addition, only N. delicatulus and two species of the N. xanthographus species group (N. dissimulator and N. marvaldiae) have distinct sclerites in the endophallus, which consist of a pyriform piece flanked by two wing-like pieces (Cyrtomon-like, see Lanteri & del Río, 2017b); this feature correlates with a spermatheca of different shape (i.e., with a long subcylindrical collum).
A phylogenetic analysis by del , suggests that the N. leucoloma species group is probably monophyletic and closely related to the N. purpureoviolaceus and N. auricinctus species groups; the N. tarsalis species group (represented by N. cyphoides) may be close to the N. cinereidorsum species group; and the two subgroups of the N. xanthographus species group do not form a clade. Even if future studies reveal that some species groups of Naupactus herein described are not natural, we believe that their recognition is useful in facilitating species identification, and in testing phylogenetic hypotheses in a historical biogeographic context (see del Río, Morrone & Lanteri, 2015;.