Dromochorus chaparralensis, Duran & Herrmann & Roman & Gwiazdowski & Drummond & Hood & Egan, 2019

Duran, Daniel P., Herrmann, David P., Roman, Stephen J., Gwiazdowski, Rodger A., Drummond, Jennifer A., Hood, Glen R. & Egan, Scott P., 2019, Cryptic diversity in the North American Dromochorus tiger beetles (Coleoptera: Carabidae: Cicindelinae): a congruence-based method for species discovery, Zoological Journal of the Linnean Society 186, pp. 250-285 : 274-275

DROMOCHORUS CHAPARRALENSIS DURAN, ROMAN, HERRMANN & EGAN SP. NOV.

( FIG. 9E )

Common name

Chaparral tiger beetle.

Type locality

Carrizo Springs, TX . Holotype (deposited in NMNH): 1 ♀, Carrizo Spgs/Tex. V-27–32 // E. G. Lindsley Collector // M.A. Cazier/Collection . Paratypes: 3 ♂♂, 5 ♀♀, Carrizo Spgs./Tex VI-12–32 // E.G. Lindsley Collector // A. Nicolay collection 1950. 1 ♀, Mexico, Tamaulipas/Nuevo Laredo/20-VI-2010/leg J. Stamatov. 1 ♀, USA: Texas: LaSalle Co./Chaparral W.M.A./19-VI- 2013/E. San Gregario. Fig. 9E , Map Fig. 3

Distribution

Inland South Texas (currently known from Dimmit, LaSalle, and Webb Counties) and Tamaulipas, Mexico. This species has not been well sampled and is likely present in adjacent areas within the Gulf Coastal Plain, especially in northern Mexico. It can occur with D. velutinigrens in places where sandy soils mix with the dominant heavier red clays.

Diagnosis

Dromochorus chaparralensis is a robust, dark beetle, and most specimens are dull black with little colour on dorsal or ventral surfaces. Some specimens may have bluish reflections along the margins. It is restricted to mesquite chaparral in South Texas.

This species is most likely to be confused with D. minimus or welderensis .

Dromochorus mimimus is usually smaller ( Fig. 6 ; Table 2), and possesses a prominent frosted ashy grey, beige, or blue sheen on the dorsal surface; the pronotum has sparse thin erect setae.

Dromochorus welderensis is black with a faint dark blue sheen dorsally, in many individuals. The habitat of D. welderensis is Gulf Coast Prairie grasslands, as opposed to the more inland and forested mesquitechaparral habitat of D. chaparralensis .

Description

Medium- to large-sized Dromochorus . Body length 12.5–14.5 mm, mean ♀ 13.7 mm, mean ♂ 13.0 mm. Head slightly wider than pronotum. Head black with metallic blue to green reflections mostly limited to the lateral ridge of the supraorbital region. Fine to marked rugosity often present on the frons and vertex. All head portions glabrous except for two supraorbital setae next to each eye. Frons concave in median area, especially in male, bulging towards slightly convex near anterior margin, clearly delimited from clypeus, gradually blending into vertex. Genae black often with weak metallic green to violet reflections, with shallow, longitudinal striae, gradually ending at border of vertex. Clypeus shining black, apparently lacking coloured reflections. Male labrum tridentate with 6–8 setae, central area pale ochre-testaceous, with a thin dark-brown to black border posteriorly and sometimes anteriorly, dark-brown to black laterally; in some populations, the pale central area of the labrum may exist as a small spot, up to one-quarter of the total labrum surface; female labrum tridentate with 6–8 setae, entirely dark-brown to black with polished metallic cupreous to green reflections. All segments of maxillary and labial palpi consistently dark brown; apical segment is not darker than other segments. Antennae normal length, reaching back to humerus and basal third of elytron, slightly longer in male than female; scape dark testaceous to black with metallic reflections of violet, cupreous and green, with 2–3 apical setae; pedicel dark testaceous with metallic reflections of violet, cupreous and green, lacking any setae; flagellum dark testaceous, antennomeres 3–4 with metallic violet and green reflections, densely clothed in short white setae, antennomeres 5–11 dull-textured without metallic reflections and possessing erect setae in apical rings only, covered with fine pubescence throughout.

Thorax: Pronotum 2.6–3.4 mm in length, mean ♀ 3.1 mm, mean ♂ 3.1 mm; width 2.9–3.5 mm, mean ♀

3.4 mm, mean ♂ 3.1 mm. Pronotum dull black, slightly wider than long, widest near anterior margin, width to length ratio 1.0 to 1.1, setae sparse, mostly present along lateral third of dorsal surface; disc finely rugose, with thin but distinct median line, with well-defined shallow sulci present anteriorly and posteriorly; notopleural sutures clearly defined, not visible from dorsal view; proepisternum black, lacking prominent metallic coloured reflections, glabrous. Elytra elongate, dorsal surface convex, 7.2–8.6 mm length, mean ♀ 8.2 mm, mean ♂ 7.7 mm, shape similar in both sexes, but slightly wider in female, especially toward apical third; sutural spine absent, microserrations not present on elytral apices; elytral texture dull, with no pitting present, elytral coloration black, may have weak blue reflections along lateral margins; elytral maculations absent; subsutural foveae absent.

Legs: Pro-, meso- and metacoxae black, without or with minimal metallic reflections, numerous setae on pro- and mesocoxae, sparse on metacoxae; pro- and mesotrochanters with a single erect seta, metatrochanter glabrous, trochanters dark brown-testaceous; femora black with metallic violet reflections, densely clothed in decumbent white setae; tibiae brown, clothed with setae of two types: sparser brown-testaceous long setae and dense short decumbent white setae; two tibial spines present; tarsi brown-testaceous, first three dilated protarsomeres in male with dense greyishwhite setal pad.

Abdomen: Venter mostly black with metallic olive green and violet reflections. Decumbent setae present on ventrite 1. Ventrites 2–6 have sparse short brown erect setae present throughout, but often abraded.

Etymology

Named for the dominant mesquite-chaparral plant community found throughout the species range. Also, this species has been collected at Chaparral Wildlife Management Area, in Cotulla, Texas.

Ecology/natural history

Very little is known about this species, as most museum specimens are older, and nothing has been recorded about its ecology. The authors of this study have not observed D. chaparralensis in situ.

Figures

Figure 3. Distributionof sampled Dromochorus populations.Colours correspondto those used in Figure 1. Green = D.pilatei, pink = D. welderensis sp. nov., sky blue = D. velutinigrens, red = D. chaparralensis sp. nov., blue = D. pruininus, lime green = D. knisleyi sp. nov., orange = D. minimus sp. nov., black = D. belfragei.

Figure 6. Boxplots, by species, from morphometric data used in principal component analyses (PCA) for each of 411 individuals. PCA indicated three measurements: PC1, overall body length; PC2, shape of the pronotum; and PC3, elytral length to body length ratio, to explain 92–95% of the total variation in the dataset. Shown are targeted comparisons among two main phylogenetic groups: 1, the D. minimus–D. velutinigrens–D. welderensis–chaparralensis group; and 2, the D. knisleyi– D. belfragei–D. pruininus clade. Species labelled with the same letters did not differ significantly from each other, species labelled with ‘ab’ did not differ between other species which were significantly different. Percentages are relative contributions per analyses, and group; outliers are shown as black dots.

Figure 9. Dorsal habitus for species of Dromochorus. A, D.pruininus; B, D.belfragei; C, D. knisleyi sp. nov.; D, D. minimus sp. nov.; E, D. chaparralensis sp. nov.; F, D. welderensis sp. nov.; G, D. velutinigrens; H, D. pilatei.