Bembidion (Nothonepha) tetrapholeon, Maddison, David R., 2014

Maddison, David R., 2014, An unexpected clade of South American ground beetles (Coleoptera, Carabidae, Bembidion), ZooKeys 416, pp. 113-155 : 132-136

Taxon classification Animalia Coleoptera Carabidae

Bembidion (Nothonepha) tetrapholeon sp. n. Figs 5A, B, 9A, 15, 16, 17A, 18

Holotype

male (IADIZA), with 3 labels: "Argentina: Neuquén: Arroyo / Queñi at Lago Queñi, 830m, / 40.1575°S, 71.721°W, / 10-11.ii.2007. DRM 07.035. / D.R. Maddison, S.A.Roig", "David R. Maddison / DNA2356 / DNA Voucher" [printed on pale green paper], and "HOLOTYPE / Bembidion / tetrapholeon / David R. Maddison" [printed on red paper]. Genitalia in glycerine in small plastic vial beneath specimen; extracted DNA stored separately. GenBank accession numbers for DNA sequences of the holotype are KJ653049 (28S), KJ653145 (COI), KJ653112 (CAD), KJ653181 (Topo), KJ653215 (wg), and KJ653082 (ArgK).

Paratypes.

Total of 244, in IADIZA, MACN, MNNC, OSAC, MNHN, BMNH, EMEC, CTVR, and CMNH, from "Argentina: Neuquén: Arroyo / Queñi at Lago Queñi, 830m, / 40.1575°S, 71.721°W, / 10-11.ii.2007. DRM 07.035. / D.R. Maddison, S.A.Roig" [135 exx.], Argentina: Neuquén: Rio Pichi / Traful nr Lago Traful, 810m, / 40.4867°S, 71.5958°W, / 12.ii.2007. DRM 07.039. / D.R. Maddison, S.A.Roig" [95 exx], "Argentina: Chubut: Rio / Azul at Lago Puelo, 200m / 42.0929°S, 71.6244°W / 13.ii.2007. DRM 07.044. / D.R. Maddison" [12 exx], " Argentina: Chubut: Rio / Azul at Lago Puelo, 200m / 42.0929°S, 71.6244°W, / 13.ii.2007. DRM 07.045. / S.A.Roig, D.R. Maddison" [1 exx].

Additional material examined.

CHILE: Reg. X, Chiloé: Rio Puntra at rt 5, 55m, 42.1661°S, 73.7256°W, 19.i.2006. DRM 06.075. D.R. Maddison [5 exx, OSAC, MNNC]. CHILE: Region X, Rio Pullinque at Puente Huanehue, 8 km NE Panguipulli. 16 Jan 2002, 39.6162°S, 72.2286°W, 1590 ft. W. D. Shepard [2 exx, OSAC].

Additional identified material.

The following specimens have been examined by Luca Toledano and confirmed to belong to this species (based upon photographs we have shared). CHILE: Reg. X, Los Lagos, P.N. Vicente Péres Rosales, Petrohué, Lago Todos los Santos, 190m, mouth Rio El Caulle, 41.0924°S, 72.3950°W. 5.i.2014. L. Toledano, R. Olivieri, J.P. Morales. [1 ex, CTVR]; CHILE: Region XI, Parque Nat. Rio Simpson, H. Franz [4 exx, NHMW]; CHILE: Reg. X, I. Chiloé, R. Punta, 31.i.1986. M. Spies. [1 ex, USNM].

Type locality.

Argentina: Neuquén: Arroyo Queñi at Lago Queñi, 830m, 40.1575°S, 71.7210°W. The habitat at the type locality is a cobble, gravel, and coarse sand river shore (Fig. 6D); the river is cold and has crystal-clear water. In the same habitat members of the genus Bembidarenas Erwin are abundant, as is Bembidion (Antiperyphanes) rufoplagiatum .

Derivation of specific epithet.

From the Greek “tetra”, meaning “four”, and “pholeon”, meaning “pit”, referring to the four prominent pits visible on the underside of adults.

Diagnosis.

A large, sleek, shiny Bembidion , with an unusual body form (Figs 5A, B) of narrow forebody and large elytra. With its shape, color, and smoothness it is one of the most distinctive Bembidion species in South America, and no other known species is likely to be confused with it; it is more reminiscent of some species in New Zealand, e.g., Bembidion (Zeplataphus) dehiscens Broun ( Lindroth 1976).

Length (4.7-5.7 mm, with most specimens above 5.0 mm). Color piceous (Fig. 5A), with legs and antennae in some specimens slightly paler, and with a few specimens having a large orange spot just in front of the elytral apices (Fig. 5B).

Head with shallow and parallel frontal furrows.

Pronotum narrow, cordate, with hind angles flaring outward (Fig. 15). Very smooth, without punctures, and with a linear basolateral foveae; without distinct carina at hind angle. Lateral bead of pronotum not complete, not reaching front angle of prothorax and only in some specimens reaching the hind angle. One midlateral and one basolateral seta on each side.

Each elytron with two discal setae (ed3 and ed5); ed3 in third stria. Elytral striae with prominent punctures in their basal half, but with striae 2-7 absent in about the hind 40% or more of the elytra, such that the posterior discal seta, ed5, is in a region without striae. Striae 7 absent in many specimens. In many specimens the striae are effaced anteriorly, especially striae 2 and 3. Lateral bead of elytron effaced anteriorly, not extended onto shoulder (Fig. 16A), similar to that of Bembidion (Nothonepha) lonae (Fig. 16B), but unlike most other Bembidion (e.g., Bembidion (Nothonepha) germainianum , Fig. 16C).

Mesothorax with prominent pits in the mesepisternum (Fig. 9A), which appear internally as large intrusions that touch in the middle (Figs 10A, C, E). Smaller pits are present ventrally at the junction of abdominal segments II and III (Fig. 13A), which are evident internally as knob-like intrusions (Fig. 14A).

Hind wings full.

Microsculpture absent from entire dorsal surface of the body except for the cervical region of the head, labrum, and faintly on the clypeus; the beetles are thus brilliantly shiny. Microsculpture absent from most of the ventral surface as well, with the most notable microsculpture being on the undersurface of the head.

Aedeagus with nearly straight ventral margin, tip of variable width (Fig. 17). Prominent brush sclerite, and with flagellum not clearly evident from the left side. There is no evident correlation between aedeagal structure and presence or absence of orange spots on the elytra (compare Figs 17A, B to Figs 17C, D).

Morphological variation.

The most noted variation is in color of the elytra. Of the 257 specimens examined (including the six specimens identified by Luca Toledano), 245 have uniformly piceous elytra (Fig. 5A); the remaining 12 have a large, diffuse orange spot occupying most of the posterior third of the elytra (Fig. 5B). Ten of these orange-spotted specimens are from the three localities in Argentina, with at least one orange-spotted specimen from each locality, and two of the orange-spotted specimens are from Chile. In most of orange-spotted specimens, the posterior discal seta (ed5) is in the orange region, but immediately around the seta is a small dark spot. No other aspect of morphological or molecular variation was observed to be correlated with presence or absence of the orange spot.

DNA sequence variation.

As noted above under Results, there was minor variation present in COI and the wingless gene, and no variation in the other genes studied.

Habitat and seasonality.

At all four localities where habitat data were recorded, Bembidion tetrapholeon specimens were found on cobble, gravel, and coarse sand shores of clear, fast-flowing rivers (Fig. 6D), from 55 m elevation (Rio Puntra, Isla Grande de Chiloé, Chile) to 830 m elevation (Arroyo Queñi, Neuquén, Argentina). These shorelines lack vascular plants. The beetles occur close to the water, most within 1 m. Specimens have been found in January and February.

Geographic distribution.

In southern Argentina and Chile (Fig. 18). In Argentina this species has been found in Neuquén and Chubut, and in Chile from Regions X and XI.

Relationship to other Bembidion .

Bembidion tetrapholeon is a member of subgenus Nothonepha , as strongly supported by DNA sequences (Table 3) and the presence of shared, derived mesepisternal pits. Bembidion tetrapholeon appears to be the sister of remaining Bembidion (Nothonepha) (Figs 7, 8). Four genes support this placement (CAD, wg, ArgK, and 18S; Table 3), although the support is weak or moderate in single-gene analyses.