Bembidion paraenulum Maddison

Maddison, David R. & Arnold, Elizabeth, 2009, A review of the Bembidion (Odontium) aenulum subgroup (Coleoptera: Carabidae), with description of a new species, Zootaxa 2214, pp. 45-61 : 56-60

Bembidion paraenulum Maddison , n.sp.

( Figs 1 B–D, 4B, 5C, 5D, 6B, 7D–F, 8B)

Type Material. Holotype male (in USNM, specimen number ADP115779), labelled: " USA: Virginia: Bedford Co., Big Otter River at route 24, 175m, 37.246°N 79.3495°W, 20.iv.2004. DRM 04.026. D.R.Maddison, A.E.Arnold" / "David R. Maddison DNA 1856 DNA Voucher" [pale green paper] / "David R. Maddison V 100183 Voucher Specimen" / "Chromosomes 2n=22+XY David R. Maddison" [pale purple paper] / " HOLOTYPE Bembidion paraenulum Maddison " [red paper]. Genitalia in glycerine vial with specimen, with chromosome slide nearby; extracted DNA stored separately. GenBank accession numbers for DNA sequences from the holotype are GQ424282 (28S rDNA), GQ424254 ( COI), GQ424288 (wingless), and GQ424226 ( CAD).

Paratypes: 103 specimens from the following localities, deposited in BMNH, CAS, CMNH, CNC, CUIC, DAHC, DRM, FMNH, MCZ, MNHN, OSAC, UAIC, UASM, and USNM: Same data as holotype (25); USA: VIRGINIA: Danville City Co., Danville, Dan River at Robertson Bridge, 36.5783°N 79.4308°W (33); 36.5828°N 79.4246°W (6); 36.5788°N 79.4328°W (6); Campbell Co., Roanoke River at Brookneal, 37.0388°N 78.9463°W (2); Altavista, Roanoke River, 37.1057°N 79.2863°W (8). NORTH CAROLINA: Stokes Co., Town Fork Creek at Walnut Cove, 36.2917°N 80.1403°W (14); Rockingham Co., Dan River, Madison, 36.3750°N 79.9930°W (3); 36.3743°N 79.9918°W (6).

Type locality. USA: Virginia: Bedford Co., Big Otter River at route 24, 175m, 37.2460°N 79.3495°W. This is about 5.5 km WNW of Evington, at the mouth of Lick Run where it empties into the Big Otter River, at the NW corner of the bridge of route 24. The species is abundant there, and shares the habitat with the similarly common B. arenobilis Maddison.

Nomenclatorial notes. This is the species called " Bembidion sp. nr. aenulum " in Maddison (1993).

Diagnosis. Most specimens larger than specimens of B. aenulum ( Fig. 4 C). Prothorax more parallel sided than B. aenulum , and more rounded sides ( Figs 5 C, D); base of pronotum more evidently narrower than elytra ( Fig. 4 B); pronotum more convex, with front angles more depressed; laterobasal depressions deeper, and more evident ( Figs 5 C, D). Humeral sulcus of elytron medially diverging more from basal margin of pronotum than in B. aenulum ( Figs 5 C,D). Shallower microsculpture than B. aenulum , and thus shinier, most notably on pronotum. Mentum tooth narrower, more parallel-sided ( Fig. 6 B). Male aedeagus longer, with narrower and less blunt apex than B. aenulum ( Figs 7 D–F); ventral sclerite patch with dorsal ridge straighter, and meeting the ventral margin of the anterior basin at an angle ( Fig. 8 B, VSP); right lobe of central sclerite complex less rounded ( Fig. 8 B, CSC right lobe).

Additional characteristics. ABL 3.8 to 5.0 mm, with most specimens longer than 4.3 mm. Color as in B. aenulum , except often with a less-intense metallic reflection, which is also rarely as gold or reddish as in B. aenulum , and more frequently greenish. Other characteristics as in the subgroup description. Chromosome number is 2n = 22+XY (three males examined, two from Virginia: Danville, and the holotype).

Geographic variation. The smallest specimens (3.8 mm) are males from New Hampshire. Specimens from the other regions are all larger than 4.1 mm. Specimens from Mississippi have larger, more convex, and wider prothoraces (compare Fig. 5 D to Fig. 5 C).

Specimens from the three geographic regions also differ in DNA sequences. The three New Hampshire specimens have three unique bases in COI (1 of which is a unique within the other Bembidion sampled, and thus possibly a synapomorphy), the Mississippi population has 2 unique bases (both of which are unique within Bembidion ), and the Virginia/North Carolina populations have three unique bases, none of which are unique within Bembidion . Thus, sequences from the three regions differ consistently, one from each other, by five or six bases out of the 762 bases sequenced for all specimens.

In 28S, site 496 of the analyzed sequence varies between geographic regions. This site is the tenth in the sequence CACTTCTCCCCTTGTAGGA. All specimens of B. paraenulum examined contain 28S copies with this sequence within their genomes, as all specimens have a dominant peak of a C at that site in chromatograms. In addition, most specimens have a secondary peak of T at that site, suggesting they also contain some 28S copies with the sequence CACTTCTCCTCTTGTAGGA. In the Virginia, North Carolina, and Mississippi specimens, the T peak is less than 7% of the C peak, suggesting that almost all of the copies of ribosomal DNA in the genome have C at that site, with only a few copies having T. In contrast, the three New Hampshire specimens have the T peak 19–50% of the C peak, indicating a higher fraction of the copies are likely T at that site in New Hampshire.

Habitat. We have collected this species at nine localities in New Hampshire, Virginia, North Carolina, and Mississippi along rivers and creeks on pure sand shores, or sand with some gravel ( Figs. 1 B–D). In most localities in Virginia and North Carolina it occurs in the company of B. arenobilis .

Material examined ( Fig. 9 , circles). 222 in total. In addition to the type material, specimens were examined from the following localities: USA: NEW HAMPSHIRE: Hillsborough Co., Souhegan River, Merrimack, 42.8610°N 71.4924°W (13). NORTH CAROLINA: Wayne Co., The Cliffs State Park (21). GEORGIA: Clarke Co., Whitehall Forest (8); Ware Co., 8 mi NW Waycross, US 23 & US 1 at Satilla R. (7). FLORIDA: Liberty Co., 1 mi W of Bristol, Apalachicola River (1); Torreya State Park Primitive Campsite, Apalachicola River (3); Santa Rosa Co., Blackwater River State Park (1); Suwanee Co., Suwanee River at route 249 (5); Suwanee River State Park (1). ALABAMA: Baldwin Co., Dixie Landing, Alabama River, 8 km W Chrysler (1); Monroe Co., 3.5 mi S Uriah, Little River (2). MISSISSIPPI: Stone Co., 12 mi E Wiggins on Hwy 26, Black Creek (6); Red Creek W.M.A., near Wiggins, 30.774°N 88.914°W (21); Red Creek X hwy 15 (16); Covington Co., Okatoma Creek, south of Seminary (5); Okatoma Ck at Lux (2/ 3 mi N. Co. line) (2); Okatoma R. near Lux (1); Walthall Co., 5 mi SE Lexie (2); Perry Co., DeSoto N.F., Black Creek at Fairley Bridge Landing, 30.9197°N 88.9661°W (10); 5.9 mi S Tylertown, Magees Creek, 31.0414°N 90.1922°W (2). In addition, there is a specimen in the MCZ labelled "Mo", presumably an abbreviation for Missouri, and another in the H.C. Fall Collection at the MCZ labelled "Wis", presumably for Wisconsin, both of which belong to this species. Missouri and Wisconsin are both notably outside the otherwise-known range ( Fig. 9 ); we suspect those specimens are mislabelled. If valid, however, these localities would suggest that B. aenulum and B. paraenulum might be sympatric.

Figures

FIGURE 1. Habitat of Bembidion aenulum (A) and Bembidion paraenulum (B – D). A: USA: Iowa: Webster Co., Des Moines River near Stratford. B. aenulum occurs in the coarse, well-drained sand; the river bank also houses Bembidion integrum Casey, B. chalceum, B. cordatum LeConte, B. grandiceps Hayward, B. confusum, and B. rapidum LeConte. B: USA: New Hampshire: Hillsborough Co., Souhegan River, Merrimack. B. paraenulum is found on the sand island on the right along with B. carinula, B. chalceum, B. inaequale Say, and B. nigrum Say. C: Type locality of Bembidion paraenulum, USA: Virginia: Bedford Co., Big Otter River at route 24. Bembidion (Pseudoperyphus) arenobilis Maddison is also abundant in this habitat. The substrate here consists of coarse sand with some gravel. D: USA: Mississippi: Walthall Co., 5.9 mi S Tylertown, Magees Creek. B. paraenulum occurs on the pure sand banks.

FIGURE 4. Male habitus. A: Bembidion aenulum, DRM voucher V 100128, Iowa: Des Moines River near Stratford. B: Bembidion paraenulum, DRM voucher V 100078, New Hampshire: Merrimack. C: Specimens of each species showing typical size difference: Bembidion aenulum (left), DRM voucher V 100129, Iowa: Des Moines River near Stratford and B. paraenulum (right), DRM voucher V 100130, USA: North Carolina: Rockingham Co., Dan River, Madison.

FIGURE 5. Pronota and elytral shoulder. A: Bembidion aenulum, DRM voucher V 100515, Iowa: Des Moines River near Stratford. B: Comparison of shoulder area and hind pronotal angle of B. aenulum and B. paraenulum. Note how the humeral sulcus is nearly parallel to the hind margin of the pronotum in B. aenulum, whereas in B. paraenulum the sulcus diverges from the pronotal hind margin toward the middle of the beetle. This also means that mesal end of the sulcus points more posteriad in B. paraenulum than B. aenulum. C: B. paraenulum holotype, Virginia: Big Otter River. D: B. paraenulum, DRM voucher V 100126, Mississippi: Perry Co., DeSoto N. F., Black Creek at Fairley Bridge Landing. All photographs to same scale; scale bar is 0.5 mm.

FIGURE 6. Ventral surface of mentum. A: Bembidion aenulum, DRM voucher V 100290, Iowa: Des Moines River near Stratford. B: B. paraenulum, DRM voucher V 100293, Virginia: Big Otter River at route 24. Drawings to same scale; scale bar is 0.1 mm.

FIGURE 7. Aedeagus, left side, of Bembidion aenulum (A – C) and B. paraenulum (D – F). A: B. aenulum, DRM voucher V 100290, USA: Iowa: Webster Co., Des Moines River near Stratford. B: B. aenulum, DRM voucher V 100291, USA: Iowa: Jones Co., Wapsipinicon River W of Oxford Junction. C: B. aenulum, DRM voucher V 100292, USA: Iowa: Cedar Co., Cedar River at route X 40. D: B. paraenulum, DRM voucher V 100293, USA: Virginia: Bedford Co., Big Otter River at route 24. E: B. paraenulum, DRM voucher V 100295, USA: New Hampshire: Hillsborough Co., Souhegan River, Merrimack. F: B. paraenulum, DRM voucher V 100514, USA: Mississippi: Stone Co., Red Creek W. M. A., near Wiggins. All to same scale; scale bar is 0.1 mm.

FIGURE 8. Details of internal sac of male genitalia, showing central sclerites, from left side. Consistent differences between two species indicated with arrows. A: Bembidion aenulum, DRM voucher V 100291, USA: Iowa: Jones Co., Wapsipinicon River W of Oxford Junction. B: B. paraenulum, DRM voucher V 100293, USA: Virginia: Bedford Co., Big Otter River at route 24. VSP: Ventral sclerite patch; CSC: Central sclerite complex.

FIGURE 9. Geographic distribution of Bembidion aenulum (stars) and B. paraenulum (circles). Black symbols represent specimens identified using DNA sequences and morphological data; gray symbols are those identified only with morphological data. The open circles represent specimens of B. paraenulum, but with labels only indicating the state; these localities are considered questionable as they are so far outside the well-documented range of this species.