Hexurella encina Gertsch & Platnick, 1979

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 encina Gertsch & Platnick, 1979

Fig. 14

Hexurella encina Gertsch & Platnick (1979): 30, figs 73, 75, 86-88 (Dm).

Material examined.

Near-type locality material: MEXICO - Baja California Norte • 5♀, 1 imm; Hwy 3, just N Ejido Zapate, N end Guadalupe Valley , 32.1692, -116.5056; 25 Mar. 2022; M. Hedin, R. Monjarez Ruedas, R.W. Mendez leg.; MCH 22_024 • 5♀, 8 imm; Hwy 3, just N Ejido Zapate, N end Guadalupe Valley , 32.1692, -116.5056; 15-16 Jan. 2023; M. Hedin, D. Leavitt leg.; MCH 23_001. Non-type material : - Baja California Norte • 5♀, 1 imm; road to Cerro Bolla, southeast of Valle de Las Palmas , 32.3300, -116.6454; 25 Mar. 2022; M. Hedin, R. Monjarez Ruedas, R.W. Mendez leg.; MCH 22_023 .- Baja California Norte • 7♀, 4 imm; road to Sierra San Pedro Martir, W of Hacienda Sinaloa, 30.9815, -116.0960; 28 Mar. 2022; M. Hedin, R. Monjarez Ruedas, R.W. Mendez leg.; MCH 22_037 .

Diagnosis.

Easily distinguished from sister taxon H. uwiiltil sp. nov. in that the H. encina male femur I lacks spines on the prolateral surface ( Gertsch and Platnick 1979, fig. 86); see H. rupicola diagnosis above for differences between H. encina and H. rupicola .

Description of previously undescribed

♀ (SDSU_TAC000681; Fig. 14B, C ). Total length (including chelicerae) 4.10, cephalothorax and appendages dirty light brown (in alcohol), legs blotched with pigment. Eye tubercle with dark pigmentation beneath. Fangs concolorous dusky, clothed with long, basal hairs projecting inwards. Abdomen mottled dark purple with whitish background, densely covered with fine hairs. Tergal plates slightly lighter than abdomen, anterior oval plate covering most of abdominal width, posterior oval plate covering ~ 1/3 of abdominal width, both plates covered with fine hairs. Carapace (including chelicerae) 1.87 long, 1.37 wide, suboval in shape as viewed dorsally, gently rounded in front, slightly invaginated behind. Low and convex viewed laterally, inconspicuous fine hairs in ocular region and along carapace edges, without evident cephalic grooves, conspicuous inward-pointed triangular mottled pigmentation above three front leg coxae. Thoracic groove shallow, linear, slightly pigmented,0.2. Eyes set on low tubercle, ~ 1/3 width of anterior carapace, offset from anterior carapace edge by approximately same distance as tubercle length. Anterior lateral eyes ~ 1/3 third larger than all others, themselves ca. equal in size. Anterior eye row procurved, posterior eye row approximately straight. Sternum 0.9 long, 0.8 wide, sparsely covered with long hairs, sternal sigilla not obvious. Labium 0.1 long, 0.4 wide, gently rounded along whitish anterior edge, with forwards-projecting hairs. Endites 0.45 long, 0.4 wide, whitish and thickened medially, conspicuous forward projecting hairbrushes on prolateral edge. Chelicerae 0.7 long, 0.3 wide at base (viewed from above), promargin with three large teeth, microteeth between, retromargin with two basal microteeth. 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 3.4 (1.18, 0.6, 0.8, 0.5, 0.4). Palp (prolateral view) total length 2.2 (0.9, 0.4, 0.5,0.6), clothed with long hairs, four spines on ventral tibia. Abdomen 2.2 long, 1.3 wide, suboval, somewhat flattened. Posterior median spinnerets slightly shorter than anterior laterals, posterior lateral spinnerets tapering, four-segmented, third segment slightly longer than others and pseudo-segmented. Spermathecae with medial and lateral receptacles ca. equal length; small pockets lateral to receptacles blunt-tipped (Fig. 14C ).

♀ Variation.

Females conspicuously large, with specimens from west of Hacienda Sinaloa (MCH 22_037) the largest females we have seen for this genus.

Distribution and natural history.

Spiders at the Ejido Zapate locale were found to be exceedingly common under rubble and small stones in very exposed situations in coastal sage scrub (Fig. 14D ). While collections here are from winter and spring months, these microhabitats must be extremely dry in the summer, and we hypothesize that these small spiders retreat into small void spaces deeper in the soil matrix during these times. At all localities Hexurella encina was observed making webs directly out of small voids in clay banks without connecting leaf litter, reminiscent of scaled-down versions of the retreats sometimes created by Megahexura fulva in mesic habitats to the north.

The Cerro Bolla and Hacienda Sinaloa collections were from north-facing situations with richer plant communities, and webs were frequently made in a matrix of both leaf litter and millipede frass at the later collection (Fig. 14E ). Plants providing shade and litter include Malosma laurina (Nutt.) Nutt. Ex Abrams (Laurel Sumac) and Rhus integrifolia (Nutt.) W.H. Brewer & S. Watson (Lemonade Berry) at Hacienda Sinaloa, and Quercus agrifolia Née at Cerro Bolla.

The larger sizes seen in H. encina and H. uwiiltil sp. nov. may be an adaptation for the exposed microhabitats they inhabit and the increasingly arid conditions moving south into Baja California Norte. The larger size could help with water loss as the surface area/volume ratio shrinks.

Discussion.

Gertsch and Platnick (1979) cite the type (and then only known) locality for H. encina as " 40 mi. south of Tecate, Baja California, Norte ". The main highway from Tecate (Hwy 3) goes approximately straight south, with our Ejido Zapate (N end Guadalupe Valley, MCH 22_024, MCH 23_001) collections being very close to this distance from the border. We presume that these collections represent H. encina and describe the previously unknown female from here. Despite collecting attempts at this and several other locations we have not yet collected an adult male H. encina .

The southernmost record for this species (west of Hacienda Sinaloa, MCH 22_037) is south of the type locality of Hexurella uwiiltil sp. nov. (Fig. 3 ). Males are unknown for the Hacienda Sinaloa location, and specimens from this location are somewhat phylogenomically divergent from northern locations for H. encina (Figs 1 , 2 , 4 ). It will be important to collect adult males from this location.

Conservation status.

Likely secure, and likely with a larger distribution than currently known.

Figures

Figure 1. Ingroup-only UCE concatenated ML tree. Specimen numbers correspond to those in Suppl. material 1. Nodal values correspond to bootstrap / gCF / sCF (gCF and sCF values rounded to nearest integer). Inset upper left - Rooted ML tree with bootstrap values shown for primary lineages (see also Suppl. material 4). Inset upper right - adult male Hexurella rupicola (San Diego County, CA).

Figure 2. Ingroup-only UCE ASTRAL species tree. Specimen numbers correspond to those in Suppl. material 1. Included are local posterior probability values. Branch lengths in coalescent units for internal branches only, terminal branch lengths arbitrary.

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 4. Mitochondrial COI time tree, based on 2.5 % substitution rate analysis. Bootstrap values from whole mitogenome phylogenetic analysis (see Suppl. Material 5). Upper left inset: Density plot of tree root heights estimated using different COI substitution rate values.

Figure 14. H. encina A ♀ live (NE end Guadalupe Valley, MCH 23 _ 001) B ♀ dorsal view (SDSU _ TAC 000681, NE end Guadalupe Valley) C ♀ spermathecae (SDSU _ TAC 000681, NE end Guadalupe Valley) D near type locality habitat (NE end Guadalupe Valley, MCH 23 _ 001), spiders common under rocks along bank E web (road to Sierra San Pedro Martir, MCH 22 _ 037).