Hexurella xerica, Monjaraz-Ruedas & Mendez & Hedin, 2023

Monjaraz-Ruedas, Rodrigo, Mendez, Raymond Wyatt & Hedin, Marshal, 2023, Species delimitation, biogeography, and natural history of dwarf funnel web spiders (Mygalomorphae, Hexurellidae, Hexurella) from the United States / Mexico borderlands, ZooKeys 1167, pp. 109-157 : 109

Hexurella xerica sp. nov.

Figs 11 , 12

Material examined.

Type material: Holotype: USA - California, San Bernardino Co. • ♂ holotype; Ord Mountains, Ord Mountain , Sweetwater Spring , 34.6918, -116.8235; 14 Feb. 2022; R.W. Mendez leg.; RWM 22_014 . Paratype: - San Bernardino Co. • ♀ paratype; Stoddard Ridge, Traer Agua Canyon, 34.6716, -116.9962; 7 Apr. 2023; R.W. Mendez leg.; RWM 23_034 . Non-type material: - San Bernardino Co. • 2 imm; Ord Mountains , Ord Mountain , Sweetwater Spring , 34.6918, -116.8235; 14 Feb. 2022; R.W. Mendez leg.; RWM 22_014. - San Bernardino Co. • 3♂, 1 imm; Ord Mountains , Ord Mountain , Sweetwater Spring, 34.6918, -116.8235; 8 Apr. 2023; R.W. Mendez leg.; RWM 23_035. - San Bernardino Co. • 3♂, 3♀, 1 imm; Stoddard Ridge, Traer Agua Canyon, 34.6716, -116.9962; 7 Apr. 2023; R.W. Mendez leg.; RWM 23_034. - San Bernardino Co. • 4♂, 4♀, 4 imm; Stoddard Mtn, below summit, 34.7003, -117.1236; 6 Apr. 2023; R.W. Mendez leg.; RWM 23_033 .

Diagnosis.

Easily distinguished from sister taxon H. ephedra in that the male palpal tibia includes only three thick, distal retromarginal spines (Fig. 11B, D F), and male femur I includes a row of 4-7 spines noticeably high on the prolateral face (Fig. 11A, C, E ).

Description of ♂ holotype

(SDSU_TAC000679; Fig. 11A, B ; Fig. 12A ). Total length (including chelicerae) 2.2, cephalothorax and appendages pale cream (in alcohol). Eye tubercle with dark pigmentation beneath. Fangs cream-colored like cephalothorax, with long, basal to medial hairs projecting inwards. Abdomen darker than cephalothorax, hint of circular blotches beneath integument, evenly covered with fine hairs. Tergal plates barely lighter than abdomen, anterior rectangular plate covering most of abdominal width, posterior oval plate covering ~ 2/3 abdominal width, both plates covered with fine hairs. Carapace (including chelicerae) 1.05 long, 0.8 wide, sub oval to circular in shape as viewed dorsally, gently rounded in front, slightly indented behind. Low and convex viewed laterally, very sparse fine hairs on lateral posterior margins, without evident cephalic grooves, dorsal pigmentation (in alcohol) mostly lacking. Thoracic groove very shallow, linear, barely pigmented, 0.075. Eyes set on low tubercle, ~ 1/3 width of anterior carapace, offset from anterior carapace edge by distance equal to length of tubercle itself. Anterior lateral eyes ~ 2 × larger than all others, themselves ca. equal in size. Anterior eye row procurved, posterior eye row approximately straight. Sternum 0.5 long, 0.5 wide, sparsely covered with hairs concentrated on lateral edges, sternal sigilla not obvious. Labium 0.1 long, 0.2 wide, with forwards-projecting hairs. Endites 0.225 long, 0.2 wide, whitish, and thickened medially, forward projecting hairbrushes on prolateral edge. Chelicerae 0.3 long, 0.1 wide at base (viewed from above), promargin with five large teeth, microteeth between distalmost pair, retromargin with one basal microtooth. Leg formula 4132. All legs clothed with fine hairs, legs III and IV with more numerous spines on all surfaces, and with conspicuous spines distally. Leg I thickened, with femur 1/3 as deep as long, prolateral surface of femur with dorsal row of 4 spines (Fig. 11A ), tibia and metatarsus with three and two ventral spines, respectively. Leg I (prolateral view) total length 2.1 (0.675, 0.4, 0.5, 0.4, 0.3). Palp total length (prolateral view) 1.3 (0.5, 0.2, 0.4, 0.3). Palp clothed with fine pale hairs and weak spines; tibia thick, cylindrical, two times as long as deep, three thicker retromarginal spines on distal edge. Abdomen 1.2 long, 0.8 wide, suboval, somewhat flattened. Posterior median spinnerets slightly shorter than anterior laterals, posterior lateral spinnerets tapering, four-segmented. Embolus closely appressed to the conductor (viewed at 10X magnification).

Description of ♀ paratype

(SDSU_TAC000696; Fig. 12B, C ). Total length (including chelicerae) 5.00, cephalothorax and appendages pale tan (in alcohol). Eye tubercle with dark pigmentation beneath. Fangs pale cream, clothed with long, basal hairs projecting inwards. Abdomen slightly darker than cephalothorax, evenly covered with fine hairs. Tergal plates ca. same color as abdomen, anterior oval plate covering most of abdominal width, posterior oval plate covering ~ 1/3 of abdominal width, both plates with fine hairs. Carapace (including chelicerae) 2.00 long, 1.50 wide, sub oval in shape as viewed dorsally, gently rounded in front, slightly invaginated behind. Low and convex viewed laterally; mostly without hairs, a few fine hairs along lateral margins, without evident cephalic grooves, dorsal pigmentation (in alcohol) mostly lacking. Thoracic groove shallow, linear, slightly pigmented, 0.125. Eyes set on low tubercle, ~ 1/3 width of anterior carapace, offset from anterior carapace edge by distance equal to depth of tubercle itself. Anterior lateral eyes ~ 3 × larger than all others, themselves ca. equal in size. Anterior eye row procurved, posterior eye row approximately straight. Sternum 0.7, long 0.6 wide, sparsely covered with long hairs, sternal sigilla not obvious. Labium 0.1 long, 0.3 wide, gently rounded along whitish anterior edge, with forwards-projecting hairs. Endites 0.35 long, 0.3 wide, whitish and thickened medially, conspicuous forward-projecting hairbrushes on prolateral edge. Chelicerae 0.6 long, 0.3 wide at base (viewed from above), promargin with three large teeth, microteeth between; retromargin with one basal larger tooth. Leg formula 4132. All legs clothed with fine hairs, legs I and II mostly without dorsal or lateral spines but with ventral spines on tibia and metatarsus, legs III and IV with more numerous spines on all surfaces, and with conspicuous spines distally. Paired tarsal claws with 5-7 microteeth. Leg I (prolateral view) total length 2.9 (0.95, 0.5, 0.7, 0.5, 0.4). Palp (prolateral view) total length 1.8 (0.7, 0.3, 0.4, 0.5). Palp clothed with long hairs, four weak spines on ventral tibia. Abdomen 3.0 long, 1.9 wide, sub oval, somewhat flattened. Posterior median spinnerets ca. equal in length to anterior laterals. Posterior lateral spinnerets tapering, four-segmented, third segment slightly longer than others and pseudo-segmented. Spermathecal receptacles appear to be bifurcate, with outer receptacles longer than inner receptacles (Fig. 12C ). The inner and outer-most portions are dimpled, suggesting connections to surrounding glands.

Variation.

Males from Stoddard Ridge and Stoddard Mountain locations have more femur I spines than topotypic males (Fig. 11C, E ), but possess a similar retrolateral palpal comb.

Distribution and natural history.

Known only from three adjacent locations in the Mojave Desert of southern San Bernardino County (Fig. 3 ). The type locality, Sweetwater Spring, is a seep at the bottom of a steep, andesite canyon with a large thicket of Forestiera pubescens Nutt. (Stretchberry; Fig. 12D, E ). The bottom of the ravine consists of a thick layer of litter with a minimal amount of soil over a mixture of smooth, fine-grain gravels of varying sizes. Spiders were found under small-medium sized rocks deep in the thicket, with typical Hexurella webs constructed in the gravel and dried leaves. The Stoddard Ridge locale has similar geology, but with numerous, short, winding canyons. Small pockets of spiders were found infrequently under rocks along wash edges, often in Prunus fasciculata (Torr.) A. Gray (Desert Almond) litter. The Stoddard Mountain locale was the most exposed, a northeast facing rhyolitic hillside of loosely buried talus with Ephedra sp., Phacelia distans Benth. (Desert Scorpionweed), and seasonal grasses. Large, deeply set rocks away from any shelter produced spiders just as well as protected microsites, possibly owing to the deep gravel layer that covers the slopes. This could allow for H. xerica to retreat deeper underground in the summer than at other desert Hexurella locales.

Etymology.

Named to reflect the harsh, xeric conditions in which this species persists, from the Greek xeros meaning "dry, withered."

Discussion.

Males from Stoddard Ridge and Stoddard Mountain, which lie ~ 10-15 km west of the type locality, respectively (Fig. 3 ), differ slightly from topotypic males in femur I spination (Fig. 11A, C, E ). Whether or not the habitat between these locations is contiguous is unknown, and DNA evidence should be collected to test our single species hypothesis.

Hexurella xerica sp. nov. populations (Ord Mtn., Stoddard Mtns) are found approximately 50 km north of Hexurella ephedra sp. nov. populations (Granite Mtns), possibly separated by low elevation desert habitats of the northern Lucerne Valley (Fig. 3 ). The morphological and phylogenomic distinctiveness of two previously unknown species in such geographic proximity is surprising. The many dozens of additional isolated mountain ranges in the adjacent Mojave Desert suggests the potential to uncover a radiation of undiscovered, microendemic species in this region.

Conservation status.

Currently known only from three adjacent desert locations and therefore of potential conservation concern.

Figures

Figure 3. Map of all collection localities. Phylogeographic lineage names for H. apachea as in text. The unsampled type locality of H. pinea is designated with a special symbol; all other type (or near type) localities were sampled, see text.

Figure 11. H. xerica sp. nov. A ♂ leg I, prolateral view, holotype (SDSU _ TAC 000679) B ♂ palp, retrolateral view, holotype (SDSU _ TAC 000679) C ♂ leg I, prolateral view (Stoddard Ridge, RWM 23 _ 034) D ♂ palp, retrolateral view (Stoddard Ridge, RWM 23 _ 034) E ♂ leg I, prolateral view (Stoddard Mtn, RWM 23 _ 033) F ♂ palp, retrolateral view (Stoddard Ridge, RWM 23 _ 033).

Figure 12. H. xerica sp. nov. A ♂ holotype (SDSU _ TAC 000679), dorsal view B ♀ paratype (SDSU _ TAC 000696), dorsal view, C ♀ paratype spermathecae D type locality (Sweetwater Spring) microhabitat E type locality (Sweetwater Spring) macrohabitat.