Nesticus dilutus 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 dilutus Gertsch, 1984

Fig. 23A-C

Nesticus dilutus Gertsch, 1984: 27, figs 94-96; Hedin and Dellinger 2005: 10, figs 13, 14.

Material examined.

New collections from type locality: USA - Tennessee, Rhea Co. • 2♂, 10♀; Grassy Creek Cave, south of Old Washington; 23 Aug. 1992; M. Hedin, J. Hedin leg.; Non type material: - Rhea Co. • ♀; Starve Rock Cave (TRH7); 26 Mar. 2016; K.S. Zigler, M.L. Niemiller, N. Mann leg.; KSZ 15-566 .

Diagnosis.

A close morphological and genetic relative of Nesticus tennesseensis . This species differs most conspicuously from the former in that the basal, dorsal process of the paracymbium is absent ( Hedin and Dellinger 2005, fig. 13). The tegular apophysis has a narrow, L-shaped base with a gradually tapering tip, although this condition is found in some northern populations of N. tennesseensis (see Fig. 21B ). Epigyna very similar to N. tennesseensis , but possess more widely separated, pointed medial margins when viewed dorsally (Fig. 23B, C ) rather than the extended parallel medial margins in N. tennesseensis (Fig. 22B, D, F ), and the overall shorter (anterior to posterior) epigynal plate. More troglomorphic (depigmented, lacking median eyes, with proportionately long legs) than all known populations of N. tennesseensis (see Hedin and Dellinger 2005).

Variation.

The female specimen from Starve Rock Cave has an epigynum very similar to specimens from the type locality.

Distribution and natural history.

This troglomorphic taxon was previously known only from the type locality (Grassy Creek Cave), but is now known from two nearby caves in east-central Tennessee (Fig. 13 ). Starve Rock Cave is very near Grassy Creek Cave and may share a subterranean connection.

Remarks.

Sister to Nesticus tennesseensis on UCE trees (Figs 3 , 4 ), but N. dilutus sequences are embedded within a clade of N. tennesseensis sequences on the mitochondrial gene tree (Fig. 6 ). This latter pattern is attributed to either deep coalescence or gene tree estimation error.

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 21. Nesticus tennesseensis ♂ palps, ventral view A West Virginia, Raleigh Co., Grandview SP, MCH specimen # 1360 B Virginia, Tazewell Co., Fallen Rock Cave, MCH specimen # 1808 C Fallen Rock Cave, MCH specimen # 1807. Scale bar: 0.5 mm.

Figure 22. Nesticus tennesseensis epigynal variation. Tennessee, Grainger Co., Indian Cave, MCH specimen # 1010, ventral (A), dorsal (B). North Carolina, Surry Co., near Fisher Peak, MCH specimen # N 1126, ventral (C), dorsal (D). Tennessee, Carter Co., near Watauga Lake, MCH 05 _ 078, ventral (E), dorsal (F). West Virginia, Raleigh Co., Grandview SP, MCH specimen # 1362, ventral (G).

Figure 23. Nesticus dilutus ♂ and ♀. Tennessee, Rhea Co., Grassy Creek Cave, ♂ MCH specimen # 1307, ventral (A). Tennessee, Rhea Co., Grassy Creek Cave, ♀ MCH specimen # 1314, ventral (B), dorsal (C). Scale bar: 0.5 mm.