Notes about morphological features of the Western Hemisphere subtribe Ardistomina, and revision of genus Semiardistomis Kult (Coleoptera, Carabidae, Scaritinae, Clivinini)

Abstract Comparisons of structural features (principally mouthparts, elytral-abdominal locking mechanism, and female genitalia) of the ardistomine genera (Aspidoglossa Putzeys, Ardistomis Putzeys, and Semiardistomis Kult) with those features of members of the subtribe Clivinina (Clivina Latreille, Oxydrepanus Putzeys, Schizogenius Putzeys,Ancus Putzeys, Nyctosyles Putzeys, and Obadius Burmeister) confirm the taxonomic validity of the subtribe Ardistomina. Based on morphological features, the ardistomine genera are postulated to be related as follows: [Aspidoglossa [Ardistomis + Semiardistomis]]. Knowledge of this subtribe is further extended by taxonomic treatment of the genus Semiardistomis Kult. Of the 30 valid names of Semiardistomis previously recognized, four were proposed as variety names, and are listed as junior synonyms: Ardistomis labialis picipes Bates, 1881, Ardistomis labialis nanus Bates, 1881, and Ardistomis labialis dilatatus Bates, 1881; and Ardistomis pallipes caerulea Putzeys, 1846. Eight names, treated as specific epithets, are junior synonyms, as follows: Ardistomis (Semiardistomis) balthasari Kult, 1950 = Semiardistomis glabratus (Putzeys, 1866); Ardistomis (Semiardistomis) emdeni Kult, 1950 = Semiardistomis deletus (Putzeys, 1846); Ardistomis aenea Putzeys, 1866, Ardistomis (Semiardistomis) brittoni Kult, 1950, and Ardistomis (Semiardistomis) marani Kult, 1950 = Semiardistomis flavipes (Dejean, 1831); Ardistomis tuspanensis Putzeys, 1846 = Semiardistomis labialis (Chaudoir, 1837); Ardistomis (Semiardistomis) vlastae Kult, 1950 = Semiardistomis subglabra (van Emden, 1949); and Ardistomis striga Putzeys, 1866 = Semiardistomis pallipes (Dejean, 1831). Two new species described are Semiardistomis exspectatus sp. n. (type locality PERU, Madre de Dios, Rio Manu, 11°56'47"S, 071°17'00"W), and Semiardistomis major sp. n. (type locality PERU, Loreto, Rio Samiria, 05°12'S, 75°20'W). The 20 species of Semiardistomis are arranged intwo species–groups here proposed: the puncticollis group, including 12 species; and labialis group, including eight species. The species recognized are keyed, described or redescribed, and notes are provided about their Geographical distribution, habitat and activity. Distribution maps show known geographical ranges, from which are inferred patterns of speciation from a center of radiation in northern South America of both lineages.


Introduction
Although the major part of this paper treats the species of Semiardistomis, a more general background is provided by a preliminary treatment of the subtribe Ardistomina and comparison with other taxa of the tribe Clivinini, principally the nominotypical subtribe Clivinina. Many scaritid genera were included in the Ardistomina, but Bousquet (2006) restricted the subtribe to the genera Ardistomis, Semiardistomis and Aspidoglossa Putzeys; additional evidence presented in this work supports recognition of the group.
The quotations above provide an idea of past taxonomic difficulties regarding members Semiardistomis. Interpretations made using non-diagnostic characters from short series of specimens have led to a taxonomic system, mostly useless, in order to identify and correlate beetles of this genus. The first arrangement of the group was made by Putzeys (1866) who recognized common characters to designate his "deuxieme groupe" of genus Ardistomis Putzeys. Despite that, he placed the North American species of Semiardistomis Kult in a separate group; this structure started recognition of the group as a different entity from its generic origin. Kult (1950) corroborated Putzeys' taxonomic structure, naming the "deuxieme groupe" as subgenus Semiardistomis, which was divided into 8 groups, and the "troisieme groupe" as subgenus Ardistomiellus. Kult's structure was built using characters that proved to be superficial, so species with different origin were placed in the same group. This new scheme resulted also in inclusion of some species of the genus Ardistomis in Semiardistomis, a mistake followed by subsequent authors until Valdes (2009) made the necessary corrections. Whitehead [in Reichardt (1977)] suggested treating Semiardistomis as a distinct genus, but no formal action was taken until Nichols (1988b) did so. The last published list of species names of Semiardistomis was compiled by Lorenz (2005).

Material and methods
Study is based on 1038 specimens examined, provided by, or checked in, the following collections (names of curators or owners at the time of the loan in parentheses).
Mandible proportion is interpreted from ratio of the length of the transverse line at outer molar point (width) and length of the perpendicular distance from that line to apical edge (length).
Most terms used for structural features are found in previous works on Carabidae: Allen and Ball (1980) for adult microsculpture; Acorn and Ball (1991) for adult mandibles; Liebherr and Will (1998) for female genitalia.
Comparative morphology. Mandibles, labium, and female genitalia (source of many diagnostic features within the tribe Clivinini) were compared within the ardistomines and between that subtribe and selected members of the nominotypic Clivinina. The latter taxon was represented by Western Hemisphere members of six exemplar genera: Clivina Latreille, Oxydrepanus Putzeys, Schizogenius Putzeys, Ancus Putzeys, Nyctosyles Putzeys, and Obadius Burmeister. Also, mandibles of Dyschiriodes Jeannel (subtribe Dyschiriina) were included.
Mandibles In values for L/W (a measure of relative length), the mandibles of clivinines, dyschiriines, and the ardistomine Aspidoglossa are relatively short (L/W 1.44-1.68), whereas the mandibles of the ardistomine genera Semiardistomis (L/W 1.86) and Ardistomis (L/W 2.25) are relatively long, with a slender terebra.
The paraglossae (pg) are elongate, extended distinctly beyond the apex of the glossal sclerite (gs) in most genera of Ardistomina and Clivinina. In the ardistomine Ardistomis (Fig. 15B) and clivinine Nyctosyles (Fig. 21B) the paraglossae are much shorter than the glossal sclerite.
The glossal sclerite (gs) varies appreciably in both subtribes, being very large and rotund in Semiardistomis (Figs 13B,14B), broad with a broad apex in Nyctosyles (Fig.  21), and narrower and shorter in the remaining ardistomines and clivinines.
The glossal sclerite in the genus Semiardistomis has an extra pair of preapical setae (Figs 13B, 14B, pas). All other ardistomine and clivinine genera have a single pair of glossal setae (as).
Female genitalia: The ovipositor sclerites come in two types, either ardistomine (Figs 27-30) or clivinine (Figs 31A-36A). For clivinine genera Clivina, Nyctosyles and Obadius, the gonocoxa is segmented, each segment designated as a gonocoxite (gc1, gc2). Gonocoxite 2 is more or less falcate. In ardistomine females, in contrast, the gonocoxa (gc) is unsegmented, and slightly curved or essentially straight. The laterotergites (lt) of clivinines are more or less triangular, whereas those of ardistomines are rectanguloid. Further, the laterotergites and gonocoxites of clivinines are setose along their margins, but the apex of gonocoxite 2 is glabrous. In contrast, for ardistomines, the ovipositor sclerites are essentially glabrous, but the apex of the gonocoxa bears a few setae. An unsegmented gonocoxa with reduced number of setae is also seen in Dyschiriina (Fedorenko 1996). Within the ardistomines, the gonocoxae of Aspidoglossa and Ardistomis are moderately broad (Figs 29,30), but those of Semiardistomis (Figs 27,28) are slender, virtually rod-like.
Within the Clivinina, the reproductive tract (Figs 31A-36A) is strikingly varied, but the range of variation is about as extensive as, and similar to, that of the Ardistomina, and thus uninformative from a diagnostic perspective at subtribal level. Within each subtribe, the genera are clearly distinguishable from one another. Here, I treat only the ardistomine genera.
In Aspidoglossa females (Fig. 30), the spermathecal duct (spd) is narrow, elongate, with few loose coils proximally; the spermathecal gland (spgd) is relatively short. The female tract of Ardistomis (Fig. 29) is narrow, relatively short; the spermatheca (sp) is moderately long and markedly expanded distally. For Semiardistomis females (Figs 27, 28) the reproductive tracts of the two species-groups are sufficiently different from one another to require separate descriptions. They also differ markedly from the reproductive tracts of Aspidoglossa and Ardistomis. For details, see species-group treatments, below.
Habitat. The members of the Ardistomina are hygrophilous or mesophilous, living in riparian situations, lowland swamp forests, or wet montane tropical forest.
Microsculpture: Frontoclypeus mostly smooth; supraantennal lobes smooth; vertex with mesh pattern isodiametric; gena with mesh pattern isodiametric; gula with mesh pattern transverse. Mandibles smooth; submentum and mentum with mesh pattern isodiametric. Pronotal disc generally smooth or with mesh pattern isodiametric, microlines very shallow, marginally and smooth at the center; proepisternum smooth or with isodiametric mesh pattern, submarginal band of microsculpture absent; prosternum smooth or with mesh pattern transverse. Metasternum smooth or with mesh pattern transverse. Abdominal sterna smooth or with mesh pattern transverse. Elytra smooth or with isodiametric mesh pattern covering entirely or only part of the disc.
Chaetotaxy: Two pair of supraorbital setae (except for S. puncticollis); pronotal disc with two pair of marginal setae (except for S. puncticollis and S. viridis); except for hirsute species, setae on elytral disc located in interval 3 and S. darlingtoni (Kult) also in interval 5; abdominal sterna IV-VII with accessory setae.
Pronotum. Ovate or cordate, anterior transverse and median longitudinal impressions distinct, proepisternum visible from above, lateral border not extended to base in some specimens. Anterior transverse and median longitudinal impressions distinct. Proepipleura visible from above.
Morphological notes. Cuticular sculpture: The absence of a submarginal band of microsculpture on the proepisternum has been used to differentiate Semiardistomis from Ardistomis but the character state is not diagnostic since the band has been lost in at least two lineages of Ardistomis (Valdes 2009).
The microsculpture on the elytral disc has a diagnostic value, the absence of microsculpture being the apotypic state.
Vestiture: Hirsuteness is a common phenomenon in this genus. In the two species groups, this apotypic character state appears, its origin independently developed. In the puncticollis group, three species have hirsute structures: S. puncticollis from southern U.S.A. (supraorbital area of the head capsule, pronotal disc, elytral disc, profemur and abdominal sternum VII), S. pilosellus (Kult) from southern South America (elytral disc and profemur) and S. subglabra (van Emden) from South America (profemur). In the labialis group, two species have hirsute structures: S. viridis from southern U.S.A. (pronotal disc and elytral disc) and S. propinquus (Putzeys) from Mexico (elytral disc), Elytra: In this genus, I regard the state of having the striae complete and impunctate as plesiotypic, being present in both species groups.
Legs: Protarsomeres in males so slightly dilated that this feature is useless for sex recognition.
Male genitalia: Phallic structure enhances definition of the two species groups of Semiardistomis. See details, provided in the species-group diagnoses. The differences in the phallic structures are too small to separate the species within each group, a situation also known in other clivinine genera, such as Schizogenius Putzeys (see Whitehead 1972). Larvae. The first instar of Semiardistomis was described by Bousquet (2006). It was compared with Ardistomis larva by Valdes (2007) who pointed out two notable synapotypic features: absence of the coronal suture and a segmented maxillary palpomere 4.
Classification. Based primarily on male and female genitalic features, the species of Semiardistomis are arranged in two species-groups designated as the puncticollis and labialis group, respectively.
Criteria for species definition. Of the 20 known species of Semiardistomis only those occurring in U.S.A. (S. viridis (Say) and S. puncticollis (Dejean)) are represented by large series of specimens in collections (Nichols 1988a;Bousquet 2006). The species inhabiting Central and South America and the West Indies are represented in collections by few specimens which give only an incomplete picture of the ranges of the species.
Members of this genus are difficult to identify in part because of a shortage of useful external features, and in part because the male and female genitalia, so useful in distinguishing between species groups, are not useful within each group. Moreover, some of the characters traditionally used to separate the species have been found in large samples to vary extensively. Some samples are a mixture of combinations from extreme patterns considered as different species; being impossible to demonstrate if those populations are hybrids or simply polymorphs, while in other putative species, allopatric populations exhibit no evident differences. In the labialis group in southern South America, the species limits are especially difficult to assess probably because the group is young and composed of species with a great power of dispersal. Without direct evidence of the state of gene flow between known populations, it is almost impossible to testify in favor of the reproductive isolation of each species described or in other cases to designate subspecies. I will follow a criterion with a practical value, so maybe for some species, taxonomic determination will denote unintentionally a combination of extreme characters shared by more than one biological species.
Geographical distribution. (Figs 57-59) The range of this genus is co-extensive with the range of the Ardistomina.

The puncticollis species-group
This group is defined by the following: mentum with median carina (Fig. 13C) extended slightly distad anterior margin of lateral lobes (except S. puncticollis with this structure (putatively) reduced); mental pit organs opened through oval orifices on the mental-submental suture. Males with wide phallus, undefined basal bulb (Fig. 26B) and a prominent, thickly sclerotized endophallic basal sclerite (Fig. 26A). Female reproductive tract ( Fig. 27; cf. Fig. 28) with spermatheca duct (spd) relatively short; spermatheca (sp) bent in its middle portion, wider from this point and with acute apex.
Anterior marginal setae on pronotal disc equidistant between anterior angles and posterior setae. Elytral disc with 4 setae in interval 3. Abdominal sternum VII with ambulatory setae near base, 2 on each side; inner pair of preapical setae equidistant each other. Profemur glabrous. Ventral surface of protibia with many setae on basal half.
Clypeus with anterior margin concave medially; lateral lobes distinct, projected at the same level of anterior margin. Frontal impressions deep and wide. Supraantennal lobes with median sulci across their length. Eyes prominent. Antennomere 2 shorter than antennomere 3; antennomeres 4-10 about 1.9 times longer than wide.
Mentum with median carina extended distad slightly beyond anterior margin of lateral lobes; pit organs opened through oval orifices to the mental-submental suture.
Pronotum ovate, lateral border reaching base. Elytra oval, humeri curved, striae complete in their length, impunctate; visible humeral tooth at junction of third stria with marginal channel.
Metathoracic wings macropterous. Genitalia as described for the puncticollis species-group. Note. This species exhibits many plesiotypic character states for the puncticollis species-group.
Geographical distribution (Fig. 57). Widespread in the northern parts of South America, east of the Andes mountain range.
Habitat and activity. Records from labels suggest that the habitat of this species is typical of most species of the genus, living on loose soil adjacent to fresh water bod-ies. Furthermore the species seems to prefer sandy areas with leaves or stones. Tenerals were collected in August.
Habitat. Data from labels suggest that the species lives along standing water bodies and swamps.
Geographical distribution (Fig. 57). The known range of this species is confined to central South America.
Habitat. Nichols (1988a) reported that adults of S. laevistriatus are found under rotting bark. The species is probably associated with wet forest leaf litter.
Geographical distribution (Fig. 57). Restricted to the Islands of Guadeloupe in the Lesser Antilles.

Semiardistomis maindroni
Paratypes. two exemplars labeled as holotype (not checked) designated by Kult in "collection of National Museum of Paris (ex Maindron-Babault)".

The labialis species-group
This group is defined by the following: mentum with median carina (Fig. 14C) not extended distad, beyond anterior margin of mental tooth; mental pit organs (Fig. 14A) opened through oval orifices in basal part of mentum; male genitalia with a slender phallus (Fig.  25A) with clearly delineated basal bulb (bp) and basal sclerite (bs) of the endophallus thin and slightly sclerotized (Fig. 25B); female reproductive tract ( Fig. 28; cf. Fig. 27) with spermatheca duct (spd) relatively long, wide, bent in its distal portion, spermatheca very narrow, elongate, markedly convoluted in a series of tight twists. The species-group name is based on that of S. labialis, the type species of Semiardistomis, being this group nominotypical.

Morphological note
As in the puncticollis group, the mental carina shows a reduction pattern northward with this prolongation markedly reduced in S. viridis.

Habitat and activity.
Label data indicate that exemplars of this species have been collected during the night at margins of a small pond.
Morphological variation is observed in the elytral punctures. In three different samples from Sta Catarina, Nova Teutonia, Brazil, exemplars with this form are mixed with exemplars of S. deletus together with intermediate forms.
Geographical distribution (Fig. 58). The known range of this species is confined to a South American area south of the Tropic of Capricorn, extending from southeastern Brazil westward to western Argentina, and south to southern Uruguay.  (  Type material. Neotype, designated by Lindroth and Freitag (1969: 334), at Museum of Comparative Zoology, not examined. Type locality. Philadelphia Neck, Pennsylvania, U.S.A. Diagnosis. Body piceous with green reflections. Two pairs of supraorbital setae. More than two premedial setiferous punctures on pronotal disc. Elytral surface completely smooth, striae absent, punctures deeply impressed, setiferous. Abdominal sternum VII with 6+6 setiferous punctures. Body length given by Bousquet (2006: 11) as 5.0-6.5 mm.
Habitat and activity. I collected this species in the "Eagle trail" at the Grassy Waters Preserve in West Palm Beach on April 2, 2011. Adults were active during the day on sandy margins of a fresh water pond (Fig. 56).

A zoogeographic scenario
The distribution of the species of the puncticollis group is inadequately known because most of the species have been rarely collected (except for S. puncticollis and S. laevistriatus). Nonetheless, some patterns can be inferred. The plesiotypic state for some characters seems to be concentrated in the northern portion of South America, with putatively apotypic character states distributed peripherally in a radial fashion. This pattern is similar for the labialis species-group. Since both groups show a similar pat- tern, I postulate a possible center of origin for the genus and then radiation of descendant lineages from, Northern South America.
The northern radiant of the puncticollis species-group reached temperate southern North America through what is now Middle America (Central America + Mexico). That lineage became extinct, except for its northern descendant, S. puncticollis. An eastern lineage colonized the West Indian Lesser Antilles, evidence being the extant S. laevistriatus, which became a forest-inhabiting brachypterous humicole, confined now to the Island of Guadeloupe (Basse Terre). Incidentally, Guadeloupe houses other clivinines: Ardistomis atripennis Putzeys (macropterous) and A. guadeloupensis Kult (brachypterous); and two species of the genus Oxydrepanus.
Southward, the distributional record is too incomplete to infer patterns. Notably are localities with many sympatric species, evidencing high power of dispersal in this southern assemblage, being Loreto and Madre de Dios in Peru the localities with highest number of sympatric species.
The labialis species-group seems to follow a similar zoogeographic structure. Northward from the putative center of radiation (Fig. 59), S. viridis is the most derivative form. It is broadly sympatric with S. puncticollis, and like that species may be the oldest survivor of an interruption of the ranges of the Central American lineages. But here, contrary to puncticollis species-group, a second event arose in S. labialis and related forms in Central America, from which source originated the stock that gave rise to the West Indian Greater Antillean S. cyaneolimbatus. That stock may have reached the islands by overseas dispersal, or by means of a now foundered land bridge. More recently, the West Indian Bahamas was invaded by S. viridis, no doubt by overseas dispersal. Southward (Fig. 58) in South America, , the structurally derivative forms of the labialis species-group do not show defined patterns of speciation possibly for several reasons, including the following. First, as far as I can determine, interspecific differentiation is ruled just by some variations in the elytra surface and those variations have shown to be unstable inside localities samples checked. Second, contrary to puncticollis species-group, sympatric "species" share every grade of intermediate forms evidencing a continuous flux between populations. Probably gene flow has not been interrupted southward and we just see the result of the polymorphic condition of only one species derivate from a northern ancestor.
In both species-groups some morphological characteristics, like reduction of the prolongation of the median carina of the mentum and hirsutism, have arisen northward from center of radiation following analog ways, suggesting two different paths of evolution to those states under similar evolutionary pressures.

Checklist of the species names of the genus Semiardistomis Kult
Genus Semiardistomis Kult, 1950 Species-group puncticollis Semiardistomis cordicollis (Putzeys, 1846) Semiardistomis darlingtoni (Kult, 1950) areas mainly from South America. For sure, new samples and DNA studies will contribute to solve unclear specific status. In species-group labialis we have most of problems due to polymorphic condition of most species. In Central America S. propinquus must be evaluated using consistent genetic data to determinate whether or not it is an isolated species from S. labialis. In South America we just will be able to corroborate denominations of species S. pallipes, S. flavipes, S. deletus and S. semipunctatus when gaps in distributional records will filled with new material mainly from Amazonian and Central Brazil and meridional half of Argentina; only them, we will have data enough to picture how different characters with taxonomic value behave in relation with geographic position.