Nesticus crosbyi 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 crosbyi Gertsch, 1984

Figs 37A-D , 38A-H

Nesticus crosbyi Gertsch, 1984: 33, figs 173, 174.

Material examined.

Type material: Holotype: USA - North Carolina, Yancey Co. • ♀ holotype; Commissary Ridge Trail, 100 yards west of main peak of Mt. Mitchell ; 22 Aug. 1960; T.C. Barr leg.; AMNH; New collections from near type locality: - Yancey Co. • 2♂, 5♀; Mt. Mitchell SP, just NE summit parking lot; 35.7671°N, - 82.2641°W; 15 Aug. 1992; M. Hedin leg.; • ♂, 2♀; Mt. Mitchell SP, just NE summit parking lot; 35.7671°N, - 82.2641°W; 4 May. 1999; M. Hedin, B. Dellinger leg.; MCH 99_012; • 2♀; Mt. Mitchell SP, just NE summit parking lot; 35.7671°N, - 82.2641°W; 25 Aug. 2005; M. Hedin, R. Keith, J. Starrett, S. Thomas leg.; MCH 05_083; Non type material: - Buncombe Co. • 2♀, 3 imm; Walker branch of Dillingham Creek , drainage N of Walker Falls branch, Little Andy Creek ; 35.7677°N, - 82.3594°W; 25 Aug. 2001; M. Hedin, M. Lowder, P. Paquin leg.; MCH 01_168; • ♂, 2♀; Walker branch of Dillingham Creek , drainage N of Walker Falls branch, Little Andy Creek ; 35.7677°N, - 82.3594°W; 5 Sep. 2002; M. Hedin, M. Lowder, P. Paquin leg.; MCH 02_196; • ♀, 1 imm; SW of Cane River Gap , Hwy 197, 5 mi ENE Barnardsville; 35.8036°N, - 82.3536°W; 25 Aug. 2001; M. Hedin, M. Lowder, P. Paquin leg.; MCH 01_167; - Yancey Co. • ♂, ♀; Black Mountains , near Cattail Peak; 35.7977°N, - 82.2564°W; 4 May. 1999; M. Hedin, B. Dellinger leg.; MCH 99_012a; • 1 imm (identification based on geography and mitochondrial evidence); Blue Ridge Parkway at Bald Knob Ridge Trail, near entrance to Mt. Mitchell SP; 35.715°N, - 82.2736°W; 21 Aug. 2007; M. Hedin, M. McCormack, S. Derkarabetian leg.; MCH 07_141; • 2♂, 2♀; FR 472 along South Toe River , below Chestnut knob; 35.7265°N, - 82.2452°W; 20 Aug. 2001; M. Hedin, M. Lowder, R. McClanahan leg.; MCH 01_143; • 2♀; Mt. Mitchell SP, near Mt Craig ; 35.7776°N, - 82.2616°W; 4 May. 1999; M. Hedin, B. Dellinger leg.; MCH 99_012a; • ♀, 1 imm; Mt. Mitchell SP, off Hwy 128, between Mt Gibbes and Stepps Gap; 35.7432°N, - 82.2788°W; 26 Aug. 2001; M. Hedin, M. Lowder, P. Paquin leg.; MCH 01_170; • 1 imm (identification based on UCE and mitochondrial evidence); Shuford Creek , off Whiteoak Rd. , SW of Celo; 35.8382°N, - 82.2193°W; 21 Aug. 2007; M. Hedin, M. McCormack, S. Derkarabetian leg.; MCH 07_139; • 2♀; south of Big Laurel Mountain , N off Blue Ridge Parkway; 35.7401°N, - 82.1991°W; 20 Aug. 2001; M. Hedin, M. Lowder, R. McClanahan leg.; MCH 01_142; • ♂, 2♀, 1 imm; Prices Creek Road at Price Creek ; 35.8448°N, - 82.3869°W; 22 Aug. 2007; M. Hedin, M. McCormack, S. Derkarabetian leg.; MCH 07_149.

Diagnosis.

Male palps differ in many ways from other members of the species group (including closest relatives), with a forked base of the tegulum, a narrow, curved tegular apophysis, a beak-like basal process of the median apophysis, and a translucent dorsal paracymbial process with a relatively wide base (Fig. 37A-D ). Females have genitalia similar to members of the close-knit morphological and phylogenetic subgroup, also including Nesticus gertschi , N. secretus , and N. canei , but can be diagnosed by epigynal internal anterior plates/lobes that differ in shape (Fig. 38A-H ) and appear to lack the hypothesized vulval pockets (Vp) seen in other members of the species group (Fig. 29G-M ).

Description of ♂ from near type locality

(MCH specimen #1201). Carapace dusky cream to orange, conspicuous faint dark pigment behind ocular area and along carapace margins bleeding inwards. Legs pale yellow to cream. Abdomen mostly pale cream with crisp paired lateral pigmentation blotches. All eyes approximately equal in size, except for AMEs, ~ 1/4 width of ALEs. Eyes with rings of dark pigment. CL 1.6, CW 1.45, abdomen length 2.15, total body length 3.75. Leg I total length 9.85 (2.65, 0.65, 2.95, 2.5, 1.1), Leg formula 1423, leg I / CW ratio 6.8. Palp with forked base of the tegulum, including a short basal branch and a narrow, curved, dark, thin tegular apophysis. Median apophysis with lateral process well-sclerotized and beak-like, thin apical process. Paracymbium with well-developed triangular translucent ventral process, distal process typical for the species group, paradistal process reduced to a sclerotized low ridge, and a translucent dorsal process with a relatively wide base, mostly lacking distal serrations.

Variation.

Male variation was observed in the shape of the median apophysis lateral process, the paracymbial ventral process, and the proximal fork of the tegulum (Fig. 37A-D ). Female variation was observed in the shape of the epigynal internal anterior lobes (Fig. 38A-H ).

Distribution and natural history.

Previously known only from the type location (Mt. Mitchell), corresponding to the highest uplands east of the Mississippi River in North America, above 2000 meters in elevation. Our new records indicate that this species is more widespread in the Black Mountains (both to the north and southeast), and we include here new records from west of the Blacks, in the Great Craggy Mountains (Fig. 30 ). This demonstration of an overall larger geographic distribution, with populations also at lower elevations (e.g., Prices Creek at 930 m), has important conservation implications for this species.

Most collections have resulted in a relatively modest number of specimens taken. For example, at an apparently pristine boulderfield along the South Toe River (MCH 01_143), three persons each searching for 30 minutes collected four total adult specimens.

Remarks.

Strongly supported as a clade by UCE data (Figs 3 , 4 ), but not recovered as monophyletic on the mitochondrial gene tree (Fig. 6 ), where sequences are intermixed with sequences from close relatives Nesticus gertschi and N. canei . Mitochondrial introgression and/or incomplete lineage sorting could explain this result, as all three species occur in the same geographic region (Fig. 30 ), making lineage contact and introgression possible.

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 29. Comparative ♂ ♀ genitalia of Nesticus nasicus group species; ♂ A Nesticus nasicus B N. brimleyi C N. templetoni D N. crosbyi E N. gertschi F N. canei; ♀ G N. nasicus H N. brimleyi I N. templetoni J N. crosbyi K N. gertschi L N. secretus M N. canei. All views ventral. See subsequent figures for specimen locations and voucher details.

Figure 30. Distribution of Nesticus nasicus group species. Type localities designated with yellow circles. Primary cities shown for geographic context. Dashed lines circumscribe known species distributions; possible distribution of Nesticus secretus is tentative, see text for details.

Figure 37. Nesticus crosbyi ♂ palps. North Carolina, Yancey Co., Mt. Mitchell SP, just NE of summit parking lot, MCH specimen # 1201, dorsal (A), ventral (B) C North Carolina, Buncombe Co., Prices Creek Road at Price Creek, MCH 07 _ 149, ventral D North Carolina, Buncombe Co., Walker branch of Dillingham Creek, MCH 02 _ 196, ventral. Scale bar: 0.5 mm.

Figure 38. Nesticus crosbyi epigynal variation. North Carolina, Yancey Co., Mt. Mitchell SP, MCH specimen # 1204, ventral (A), dorsal (B). North Carolina, Buncombe Co., SW of Cane River Gap, MCH 01 _ 167, ventral (C), dorsal (D). North Carolina, Buncombe Co., Prices Creek Road at Price Creek, MCH 07 _ 149, ventral (E), dorsal (F). North Carolina, Buncombe Co., Walker branch of Dillingham Creek, MCH 02 _ 196, ventral (G), dorsal (H). Scale bar: 0.5 mm.