Bembidion brownorum Maddison, Sproul & Will, 2023

Maddison, David R., Sproul, John S. & Will, Kipling, 2023, Re-collected after 55 years: a new species of Bembidion (Coleoptera, Carabidae) from California, ZooKeys 1156, pp. 87-106 : 87

Bembidion brownorum Maddison, Sproul & Will sp. nov.

Type materials.

Holotype. Male, in EMEC, herein designated, labeled: "39.13841/-122.34621 USA: California: Colusa Co. Antelope Valley, Freshwater Creek uv light pan trap 133 m. 1.vii.2021 K.Will [Cal2021.vii.1.2]", "David R. Maddison DNA5864 DNA Voucher" [pale green paper], "HOLOTYPE Bembidion brownorum Maddison, Sproul, & Will" [partly handwritten, on red paper], "UC Berkeley EMEC 347587" [with matrix code on right side]. Genitalia mounted in Euparal in between coverslips pinned with specimen; extracted DNA stored separately. GenBank accession numbers for DNA sequences of the holotype are OQ284089, OQ286118, OQ288588, and OQ288602.

Paratypes. (13 males, 8 females). "Borax Lake, Lower Lake, Lake Co., Cal. May 14 1922" (2, CAS). "Atwater, Merced Co., Calif 15 Aug 1966" (5, CAS, OSAC). "Wood L., Tulare Co., Calif. Rotary Trap V-22-1947 Norman W. Frazier, EMEC347588" (1, EMEC). "Wood L., Tulare Co., Calif. Rotary Trap V-24-1947 Norman W. Frazier EMEC347589" (1, EMEC). "Redondo, Cal." (1, CAS). "Pasadena, Cal." (3, CAS). "San Joaquin Mill Tulare Co., Calif. May 15, 3800 ft" (2, CAS). "Azusa, Cal." (1, CAS). "Riverside, Cal. F.E. Winters" (1, CAS). "CALIF: Forest Home, San Bernardino Mts, 6000 ft. May" (1, CAS). "Poway, San Diego Co., Cal." (2, CAS). "S. Cal" (1, CAS).

Type locality.

USA: California: Colusa Co. Antelope Valley, Freshwater Creek, 39.13841°N, 122.34621°W (Fig. 5 ).

Derivation of specific epithet.

The specific epithet brownorum is treated as a noun in the genitive case and refers to Jerry and Anne Brown, former Governor and First Lady of California, respectively. The name is formed in their honor as it was their hospitality and openness to allowing access for research of insects on their ranch, the type locality, which led to the discovery of this species. Additionally, this honors their long commitment to environmentalism and continued efforts in the international climate-change movement.

Diagnosis.

A relatively large Bembidion (Notaphus) , superficially similar to B. mormon (with which it has been confused in collections), with which it shares a pale subapical band on the elytra. However, B. brownorum has a much more convex pronotum, giving it an inflated appearance; the pronotum has more rounded sides and is more constricted posteriorly. From B. callens and B. obtusangulum , in addition to the prothorax shape, it is distinguished by presence of pale elytral spots, which those two species lack.

Description

(based upon the holotype and 21 paratypes). Body length 4.4-5.0 mm. Body dark brown or dark reddish brown, with head and pronotum slightly darker than elytra; elytra each with one diffuse pale spot at about the posterior fourth. Legs uniform in color, reddish brown; antennae brown, with first antennomere paler, at least ventrally. Mentum with anterior lateral regions large, with apical portion broadly rounded, not angulate; medial tooth simple (not bifid) with truncate tip; frontal furrows weakly defined, shallow; eyes prominent (Fig. 4A ). Prothorax large, notably convex, with sides strikingly rounded such that the width at middle is much greater than the width at the posterior margin, with sides immediately front of hind angle slightly sinuate (Fig. 4B ); hind angle slightly obtuse; posterolateral carina well defined, moderately long; posterior region of pronotum slightly rugose. Elytra with lateral bead not prolonged medially at shoulder; all striae complete, striatopunctate, with much smaller punctures in the posterior half. Microsculpture present on most of the dorsal surface of the body except for the disc of the pronotum, which is glossy; evident in both sexes over entire surface of elytra, consisting of sculpticells that are slightly transverse, more deeply engraved in females (Fig. 6B ) than in males (Fig. 6A ); female elytra thus matte. Pronotum with two lateral setae on each side; elytron with two setae in third interval. Aedeagus (Fig. 6C ) typical for a member of subgenus Bembidion Notaphus .

Flight ability.

All 18 specimens examined for wing condition are macropterous. The capture of two specimens from Woodlake in a rotary trap ( Winkler 1949) and the capture of the holotype at a UV light both suggest that these beetles can fly.

Geographic variation.

None noted.

Geographic distribution.

Central Valley, Los Angeles Basin, and surrounding areas of California (Fig. 7 ). Two of the localities on the map are marked as uncertain: those labeled as from Forest Home and Redondo. The Forest Home locality is at much higher elevation than all other specimens (6000 ft). Based upon the labeling on other specimens from the F.E. Winters collection, the hand-written label attached to this specimen appears not to be an original label, and we have doubts about the validity of the data on the label. We have some doubts about the locality for the specimen labeled “Redondo”, as there are at least seven localities in California that include “Redondo” in the name (USGS Geographic Names Information System, https://edits.nationalmap.gov/apps/gaz-domestic/public/search/names). An additional locality, "San Joaquin Mill Tulare Co., Calif 3800 ft" was not mapped as we could not determine the site with any certainty.

Habitat.

The only specimen with detailed collecting data including an exact locality is the holotype. Because it was collected at a UV light, the specimen was not found in its natural microhabitat, and we do not know how far it had flown from a suitable habitat. However, the type locality might provide some hints about possible habitat of the species. The type locality lies on the east side of Antelope Valley in the northern part of the Cortina Ridge, which marks the western edge of the Colusa Basin region of the Sacramento Valley. The ridge is formed of tilted sandstone beds, mudstone, and siltstone formed from the eroded sediments of the Sierran-Klamath terrane. As members of subgenus Bembidion Notaphus are almost universally found at the edges of bodies of water (with exceptions for some species found at high elevation), we expect B. brownorum to live on lake, pond, marsh, river, or creek shores. The UV light was set up next to Freshwater Creek (Fig. 5 ), which might be the habitat of the specimen. Freshwater Creek cuts through Cortina Ridge; its bed is composed of consolidated claystone and lenses of poorly hardened conglomerate, sandstone, and siltstone. The stream is somewhat trellis-like, with persistent pools, due to the presence of minor ridges of erosion-resistant materials. The current dominant vegetation consists of grasses, cattails, willows, and rushes near the stream. Sparsely set oaks line the stream edge and lateral drainages. Water is persistent and flows on the surface in portions of the stream throughout the year. Evaporation along the stream margin intermittently creates a hardened crust of white mineral deposits that often overlays a black, highly organic mud in depositional stretches. Narrow, steep-sided sections of the stream have banks composed of exfoliating claystone and mud from eroded topsoil. The adjacent land was historically used for crop production, e.g., barley, but the land and water has primarily been used for cattle ranching. Both the stream bed and adjacent area show the impact of many years of cattle grazing. There is an historical account of beaver damming (J. Brown pers. com.) but there is presently no impact of this event. There is no evidence that the water flow has been artificially dammed, channelized, or diverted in the collection area. As such, this stretch of Freshwater Creek represents a relatively unaltered, natural, perennial source of surface water-unusual in the Central Valley and adjacent foothills of California. However, we consider evidence for B. brownorum being a stream-shore species very weak, as it is based upon only one specimen which might have flown in from some distance.

The other known localities do not clearly suggest a specific habitat, nor do the known localities of related species. Bembidion brownorum localities include a lake with sodium borate deposits (Borax Lake, Lake County), a city with a lake with extensive, flat shores (Bravo Lake in Woodlake), and a site near the Pacific Ocean that once had a salt lake (Redondo). At least the latter two are habitats similar to the saline, pond and lake shore habitats frequented by B. obtusangulum and B. mormon , near relatives of B. brownorum . The specimen labeled as from 6000 feet elevation at Forest Home, San Bernardino Mts (presumably around 34.083°N, 116.893°W) suggest instead a less saline, creek shore habit, but we doubt the veracity of that label (see above). The only specimen of the related B. callens with known habitat data is a specimen collected by Larry Stevens in gravel around the calcium-carbonate-rich waters of Havasu Springs, Arizona, at 36.2176°N, 112.6871°W (Larry Stevens pers. comm. 2022).

Figures

Figure 4. Head and pronotum of holotype of Bembidion brownorum. Scale bar: 0.5 mm.

Figure 5. Type locality of Bembidion brownorum. USA: California: Colusa Co. Antelope Valley, Freshwater Creek, 39.13841 ° N, 122.34621 ° W. Image taken November 2022.

Figure 6. Microsculpture and aedeagus of Bembidion brownorum A elytral microsculpture around seta ed 3 of holotype male B elytral microsculpture around seta ed 3 of a female from Woodlake C aedeagus of holotype male. Scale bars: 100 µm.

Figure 7. Geographic distribution of Bembidion brownorum in California. The locality indicated with a star is the type locality. The two localities indicated by gray dots are uncertain or doubtful. Darker gray areas in the base map represent higher elevations.