Torrenticola welbourni Fisher & Dowling

Fisher, J. Ray, Fisher, Danielle M., Skvarla, Michael J., Nelson, Whitney A. & Dowling, Ashley P. G., 2017, Revision of torrent mites (Parasitengona, Torrenticolidae, Torrenticola) of the United States and Canada: 90 descriptions, molecular phylogenetics, and a key to species, ZooKeys 701, pp. 1-496 : 1

Torrenticola welbourni Fisher & Dowling sp. n.

Material examined.

HOLOTYPE (♀): from USA, California, Trinity County, Shasta-Trinity National Forest, Wilson Creek (40°25'17"N, 123°3'5"W), 20 Aug 2013, by JR Fisher, JRF 13-0820-003, DNA 1638.

Type deposition.

Holotype (♀) deposited in the CNC.

Diagnosis.

Torrenticola welbourni are similar to other members of the Rusetria "Western 2-Plates" group ( T. mulleni , T. nortoni , and T. walteri ) in having anterio-lateral platelets fused to the dorsal plate, having faint dorsal coloration, and being distributed in the west. T. welbourni (only female known) can be differentiated from all other Western 2-plates by being larger (dorsal length: 690 in T. welbourni , 570-645 in others; dorsal width: 500 in T. welbourni , 415-480 in others), having more elongate pedipalp tibiae (length/width: 3.73 in T. welbourni , 3.0-3.33 in others) and longer pedipalp femora (137.5 in A30, 112.5-125 in others).

Description.

Female (Figure 274) (n = 1) (holotype only) with characters of the genus with following specifications.

Dorsum - (690 long; 500 wide) ovoid with faint orange coloration separated into anterior and posterior portions. Anterio-medial platelets (152.5 long; 57.5 wide). Anterio-lateral platelets (195 long; 72.5 wide) fused to dorsal plate. Dgl-4 closer to the edge of the dorsum than to the muscle scars (distance between Dgl-4/dorsal width 325). Dorsal plate proportions: dorsum length/width 1.38; dorsum width/distance between Dgl-4 1.54; anterio-medial platelet length/width 2.65; anterio-lateral platelet length/width 2.69; anterio-lateral/anterio-medial length 1.28.

Gnathosoma - Subcapitulum (357.5 long (ventral); 270 long (dorsal); 145 tall) colorless. Rostrum (145 long; 52.5 wide). Chelicerae (356 long) with curved fangs (70 long). Subcapitular proportions: ventral length/height 2.47; rostrum length/width 2.76. Pedipalps with tuberculate ventral extensions on femora and genua. Palpomeres: trochanter (50 long); femur (137.5 long); genu (75 long); tibia (102.5 long; 27.5 wide); tarsus (20 long). Palpomere proportions: femur/genu 1.83; tibia/femur 0.75; tibia length/width 3.73.

Venter - (820 long; 580.25 wide) colorless. Gnathosomal bay (180 long; 100 wide). Cxgl-4 subapical. Medial suture (12.5 long). Genital plates (180 long; 167.5 wide). Additional measurements: Cx-1 (324 long (total); 122 long (medial)); Cx-3 (371 wide); anterior venter (177.5 long). Ventral proportions: gnathosomal bay length/width 1.80; anterior venter/genital field length 0.99; anterior venter length/genital field width 1.06; anterior venter/medial suture 14.20.

Male unknown.

Immatures unknown.

Etymology.

Specific epithet ( welbourni ) named in honor of acarologist Cal Welbourn, who has been instrumental in teaching terrestrial Parasitengona to JRF and for teaching JRF the prostigmatan mite section of the Acarology Summer Program at The Ohio State University in 2009.

Distribution.

Only known from Trinity County, California (Figure 273).

Remarks.

Torrenticola welbourni groups with other members of the Rusetria Complex with high support. Unfortunately, only a single specimen is known of this species, so variation in COI sequence could not be investigated. This specimen was collected from the sample that contained specimens of T. walteri . It is interesting to note that these two species are the only Rusetria Complex members collected from Trinity County. In the all analyses, T. welbourni groups with the three other members of the Rusetria Complex that are found in western North America: T. mulleni , T. nortoni , and T. walteri . These species are 5-7% different in COI sequence from each other and together make up the Western 2-Plate Identification Group. Torrenticola welbourni is one of three of these that occur in California (including T. nortoni and T. walteri ).

This species hypothesis is supported by low COI divergence within the species (0-2%) and high divergence between species (3-15%), and by the morphological characters outlined in the diagnosis.