Hesperoleucus symmetricus serpentinus Baumsteiger and Moyle, 2019

Baumsteiger, Jason & Moyle, Peter B., 2019, A reappraisal of the California Roach / Hitch (Cypriniformes, Cyprinidae, Hesperoleucus / Lavinia) species complex, Zootaxa 4543 (2), pp. 221-240 : 229-230

Hesperoleucus symmetricus serpentinus Baumsteiger and Moyle , new subspecies

Red Hills Roach

( Fig. 2 )

Holotype: Museum of Wildlife and Fish Biology , University of California, Davis , WFC3050, 51.8 mm SL, Horton Creek , Tuolumne County, CA, July 16, 2010.

Paratypes. WFC3241–3244, 30.4—40.4 mm SL, same location and date as the holotype, The Red Hills Roach has strong support for a subspecies designation (e.g. Brown et al. 1992; Jones et al. 2002; Moyle 2002), especially given its increased isolation from other populations by New Don Pedro Reservoir (constructed in 1971), unique environmental constraints, and the prevalence (~97%) of the chisel-lip morphotype. Genetic and genomic analyses ( Aguilar & Jones 2009; Baumsteiger et al. 2017) also found Red Hills Roach to be highly distinct, easily distinguishable from other CA Roach. In fact, our genomic study indicated a clear break between Red Hills Roach and all other CA Roach sampled in every analysis. With so many lines of support, subspecies status is clearly warranted.

Diagnosis. Distinguished from other subspecies of H. symmetricus by their flattened body profile, smaller interorbital distance and fewer pectoral and pelvic rays ( Jones et al. 2002; Table 1). The holotype has 8 dorsal rays, 8 anal rays, 12 pectoral rays, and 8 pelvic rays.

Description. The Red Hills Roach is a genetically and morphologically distinct minnow adapted for living in small streams flowing through serpentine outcrops. They are typically small, less than 60 mm SL ( Brown et al. 1992; Jones et al. 2002) and resemble CA Roach in their general appearance. Red Hills Roach exhibit an elevated frequency of “chisel-lip”, a keratinous projection on the lower lip used for scraping algae ( Brown et al. 1992). However there is substantial temporal variation in frequency of the chisel-lip condition amongst CA Roach ( Jones et al. 2002).

Spawning coloration appears to be similar to that of CA Roach but is more intense. W. J. Jones (pers. comm.) describes it as follows: “The body is dark brown to brassy above, dark black lateral band, and brilliant white below, splashed with black blotches on the sides. Dorsal and caudal fins [are] dark olive-brown to reddish-brown, with the rays often deep-olive and with the nearly clear inter-radial membranes faintly flushed with brassy color; pectoral fins [are] yellowish with orange-red axils and very strong orange coloration at base; anal and pelvic fins [are] bright orange-red at the base with lessening coloration towards the rays. Cheeks and operculum with strong gilt reflections; strong orange coloration is found on the edges of the mouth (especially in males) with some blending into the upper mouth region. A lateral band is more strongly gilt than adjacent parts of body, thus often obscuring the lateral line. In females, the coloration is similar but less intense except for the orange coloration at the base of the paired fins that appears equally intense in both sexes. Males can be distinguished primarily by breeding tubercles on the top of the head.”

Distribution. The Red Hills Roach is confined to Six Bit Gulch and its tributary streams: Amber Creek, Horton Creek, Minnow Creek and Poor Man’s Gulch in Tuolumne Co. ( Jones et al. 2002). Six Bit Gulch, during rainy periods, flows into the western arm of New Don Pedro Reservoir on the Tuolumne River. In July 2010, Roach were observed in three discontinuous wetted reaches of Horton Creek, which covered approximately 500 meters in total wetted length (P. Moyle, unpublished observations). However, only the lower reach, which extends about 200 meters upstream from the confluence with Six Bit Gulch, appeared to be perennial (as indicated by lush growth of sedges and other riparian vegetation). A natural fish barrier approximately 1.2 km upstream from the confluence likely inhibits Roach from accessing upper Horton Creek. Roach have also been observed in Six Bit Gulch where it is forded by Six Bit Ranch Road and in a pool in Roach Creek.

Status. Red Hills Roach merit protection as a threatened or endangered subspecies and rate as an IUCN status of Critical Concern ( Moyle et al. 2011, 2015). They have an extremely limited distribution in a very harsh environment and less than 1,000 individuals persist in isolated summer pools ( Jones et al. 2002). Their persistence is threatened by fire, depleted stream flows, lack of protection on private lands, and most notably, from invasive fishes. While some habitat is protected in the Red Hills Area of Critical Environmental Concern, much is on private land along a road and remains unprotected. Red Hills Roach has persisted only because of its physiological capacity to endure the extreme environmental conditions found in these small exposed streams.

Etymology. Both the common and subspecies name reflect the nature of the rocks through which these small creeks flow. The Red Hills region is named for the color of the soils created by weathering one of the largest outcroppings of serpentine rocks in the Sierra Nevada. Serpentine soils are high in magnesium and other minerals and create conditions in which few species can live. The landscape has a sparse but highly endemic flora ( Anacker & Harrison 2012, Harrison 2013) and streams are small and largely unshaded.

Figures

FIGURE 2. Holotype of Hesperoleucus symmetricus serpentinus, Red Hills Roach. Photo courtesy of Irene Engilis.