Nesticus silvanus Gertsch, 1984

Hedin, Marshal & Milne, Marc A., 2023, New species in old mountains: integrative taxonomy reveals ten new species and extensive short-range endemism in Nesticus spiders (Araneae, Nesticidae) from the southern Appalachian Mountains, ZooKeys 1145, pp. 1-130 : 1

Nesticus silvanus Gertsch, 1984

Figs 14A-D , 15A-E

Nesticus silvanus Gertsch, 1984: 27, figs 141-143.

Material examined.

Type material: Holotype: USA - North Carolina, Jackson-Haywood Co. • ♀ holotype; Water Rock Knob summit, elev. 1918 m, 30 Oct. 1969, W. Shear leg; AMNH; New collections from type locality: USA - North Carolina, Jackson Co. • 2♂, 7♀; vicinity of Water Rock Knob, off Blue Ridge Parkway; 35.4597°N, - 83.1417°W; 9 Aug. 1992; M. Hedin leg; Non type material: - Haywood Co. • 2♂, 8♀; Blue Ridge Parkway, Mile 438, near Steestachee Bald overlook; 35.4263°N, - 83.0388°W; 13 Aug. 1992; M. Hedin leg.; • 2♀; Cold Springs Creek , NE of I-40; 35.7585°N, - 82.9938°W; 19 Aug. 2001; M. Hedin, M. Lowder leg.; MCH 01_137; • ♀, 1 imm; Fie Top Road, along Fie Creek ; 35.5451°N, - 83.1045°W; 3 Sep. 2002; M. Hedin, M. Lowder, P. Paquin leg.; MCH 02_187; • 3♀; Germany Cove Road, vicinity Hemphill Creek ; 35.5543°N, - 83.036°W; 25 Aug. 2005; M. Hedin, R. Keith, J. Starrett, S. Thomas leg.; MCH 05_087; • 2♀, 4 imm; NW Hebo Mountain , Hwy 209; 35.6869°N, - 82.9065°W; 25 Aug. 2005; M. Hedin, R. Keith, J. Starrett, S. Thomas leg.; MCH 05_086; - Jackson Co. • 6♀; Dicks Creek , near Dicks Creek Church, N of Dillsboro; 35.4056°N, - 83.2586°W; 31 Aug. 2002; M. Hedin, M. Lowder, P. Paquin leg.; MCH 02_173; • 11♀, 1 imm; Soco Creek , up Shut-in Creek road; 35.4653°N, - 83.2148°W; 3 Sep. 2002; M. Hedin, M. Lowder, P. Paquin leg.; MCH 02_188; - Macon Co. • 2♀; Falls branch of Elijay Creek , 2 mi. E Elijay; 35.2135°N, - 83.2535°W; 11 Aug. 1992; M. Hedin leg.; - Madison Co. • ♂, 12♀; Hwy 209, W Rocky Bluff campground at Long Mountain Branch ; 35.8599°N, - 82.8502°W; 19 Aug. 2001; M. Hedin, M. Lowder leg.; MCH 01_139; - Swain Co. • 14♀, 4 imm; Alarka Road, N Deep Gap church; 35.3482°N, - 83.4064°W; 28 Aug. 2002; M. Hedin, M. Lowder, P. Paquin leg.; MCH 02_168; - Tennessee, Cocke Co. • 4♀; south of Round Mountain , Shelton Branch, Hwy 107; 35.835°N, - 82.9519°W; 27 Aug. 2005; M. Hedin, R. Keith, J. Starrett, S. Thomas leg.; MCH 05_095; • 5♀; southeast of Round Mountain, W Rattlesnake Gap; 35.8472°N, - 82.9443°W; 19 Aug. 2001; M. Hedin, M. Lowder leg.; MCH 01_138.

Diagnosis.

Morphologically very similar to geographically parapatric Nesticus cherokeensis (Fig. 13 ). Males of N. silvanus can be distinguished from N. cherokeensis by the shape of the paradistal paracymbial process, which possesses a well-sclerotized ventral edge and a long prolateral extension (Fig. 14A-D ). Also, the N. silvanus paracymbium lacks a basal projection of the dorsal process (Fig. 14A, C, D ) as (sometimes) present in N. cherokeensis (Fig. 16B, F ). Epigyna of N. silvanus are very similar to those of N. cherokeensis but (when viewed dorsally) possess epigynal plates with well separated medial margins, while in N. cherokeensis these plate margins are long, parallel, and touching (but see Fig. 15E vs. Fig. 17B ). Additionally, N. silvanus epigyna possess anteriorly elongated epigynal pockets, lateral lobes that are shorter than the median septum, and relatively short spermathecae that lie perpendicular to the medium septum, separating them from remaining members of the Nesticus tennesseensis group.

Description of previously undescribed ♂ from type locality

(MCH specimen #1080). Carapace light cream colored, gray pigmentation behind ocular area leading to midline and around edges. Legs pale yellow / cream. Abdomen with paired faint gray blotches on a light gray background. All eyes approximately equal in size, except for AMEs, ~ 1/3 width of ALEs. Eyes with rings of dark pigment. CL 1.39, CW 1.16, abdomen length 1.89, total body length 3.28. Leg I total length 8.66 (2.41, 0.54, 2.48, 2.25, 0.98), leg formula 1423, leg I / CW ratio 7.5. Paracymbium possesses a hook-shaped paradistal process with a well-sclerotized ventral edge and a long prolaterally-directed extension. Paracymbial dorsal process transparent and concave. Distal paracymbial process directed anteriorly, rounded, with a serrate edge. Ventral paracymbial process triangular with a blunted anterior edge. Median apophysis oval with a sharp anterior edge. Tegular process elongate, narrowing distally, and directed anteriorly. Nose-like bulge at the base of the tegular apophysis. Distal tip of conductor bent and directed prolaterally.

Variation.

Minimal palpal variation was observed for males from three sample locations, the dorsal paracymbial process in a single Rocky Bluff male being slightly wider and shorter (Fig. 14A-D ). Female genitalic variation across sample locations was minimal (Fig. 15A-E ).

Distribution and natural history.

Originally recorded from three locations ( Gertsch 1984), now known to be relatively broadly distributed in appropriate surface microhabitats, including high-elevation habitats above 1900 m (e.g., Water Rock Knob, Steestachee Bald, etc.). This species is closely parapatric with Nesticus cherokeensis directly to the west, with an almost parallel geographic distribution (Fig. 13 ).

Strong phylogeographic structuring is observed in the mitochondrial data with a well-supported subclade found east of the Pigeon River (FieTop, Hebo Mtn, Rocky Bluff, etc.; Fig. 6 ), suggesting a possible role for riverine barriers in phylogeographic structuring, and further suggesting a southwest to northeast biogeographic directionality.

As an example of natural history, one male and 12 females were collected from rocky void spaces in a moist, rocky ravine near Rocky Bluff campground (MCH 01_139) during a 30-minute devoted Nesticus search.

Remarks.

This species is strongly supported as sister to remaining members of the Nesticus tennesseensis group based on UCE evidence (Figs 3 , 4 ).

Figures

Figure 3. UCE concatenated maximum likelihood tree. Distant outgroups removed (for graphical purposes), specimen numbers correspond to those in Suppl. material 3 (with detailed location provided in Suppl. material 1). Node numbers correspond to bootstrap (bold text) / gCF / sCF. Only bootstrap values below 100 shown, all others 100. gCF and sCF values rounded to nearest integer; sCF values below 38 highlighted with red text.

Figure 4. UCE ASTRAL species tree. Distant outgroups removed (for graphical purposes), specimen numbers correspond to those in Suppl. material 3 (with detailed location provided in Suppl. material 1). Included are quartet support values (rounded to nearest integer), and local posterior probability values (if less than 1.0, red text). Branch lengths in coalescent units for internal branches only, terminal branch lengths arbitrary. Internal branch to Nesticus cressleri truncated for graphical purposes.

Figure 6. COI IQT gene tree. Distant outgroups trimmed. Specimen numbers correspond to those in Suppl. material 3 (with detailed location provided in Suppl. material 1). Sequences from UCE capture denoted with " NODE ". Populations with a " Nesticus cooperi - like " male paracymbium denoted by small circles. Not all tip bootstrap values shown (see Suppl. material 4 for. tre file with all bootstrap values).

Figure 13. Distribution of Nesticus tennesseensis group species. Type localities designated with yellow circles. State boundaries and major cities shown for geographic context. Dashed lines circumscribe known species distributions.

Figure 14. Nesticus silvanus ♂ palps. North Carolina, Jackson Co., vicinity of Water Rock Knob, MCH specimen # 1080, dorsal (A), ventral (B) C North Carolina, Haywood Co., Blue Ridge Parkway, near Steestachee Bald overlook, MCH specimen # 1145, dorsal D North Carolina, Madison Co., W of Rocky Bluff campground, MCH 01 _ 139, dorsal. Scale bar: 0.5 mm.

Figure 15. Nesticus silvanus epigynal variation A North Carolina, Jackson Co., vicinity of Water Rock Knob, MCH specimen # 1083, ventral. North Carolina, Macon Co., Falls branch of Elijay Creek, MCH specimen # 1115, ventral (B), dorsal (C) North Carolina, Madison Co., W of Rocky Bluff campground, MCH 01 _ 139, ventral (D), dorsal (E). Scale bar: 0.5 mm.

Figure 16. Nesticus cherokeensis sp. nov. ♂ palps. North Carolina, Swain Co., Blue Ridge Parkway, below Ballhoot Scar overlook, MCH specimen # 1177, ventral (A), dorsal (B) C North Carolina, Haywood Co., S of Waterville, MCH 01 _ 134, dorsal D North Carolina, Jackson Co., Blue Ridge Parkway, near Bunches Bald Tunnel, MCH specimen # 1089, dorsal E North Carolina, Haywood Co., FR 288 above Pigeon River, MCH 01 _ 136, ventral F North Carolina, Swain Co., road to Balsam Mountain, MCH 02 _ 185, ventral. Scale bar: 0.5 mm.

Figure 17. Nesticus cherokeensis sp. nov. epigynal variation. North Carolina, Swain Co., Blue Ridge Parkway, below Ballhoot Scar overlook, MCH specimen # 1181, ventral (A), dorsal (B) North Carolina, Haywood Co., S of Waterville, MCH 01 _ 134, ventral (C), dorsal (D) Tennessee, Cocke Co., S side of Indian Camp Creek, MCH specimen # 1982, ventral (E), dorsal (F) North Carolina, Haywood Co., Cataloochee area, Sag Branch, ventral (G), dorsal (H). Scale bar: 0.5 mm.