Etheostoma rupestre Gilbert and Swain 1887

Hilburn, Bryson G., Janosik, Alexis M. & Johnston, Carol E., 2023, Incipient speciation in allopatric Etheostoma rupestre (Percidae: Etheostomatinae) lineages, with the description of three new subspecies, Zootaxa 5343 (2), pp. 151-172 : 156-159

Etheostoma rupestre Gilbert and Swain 1887

Rock Darter

Figure 8

Etheostoma (Rhothoeca) rupestre Gilbert and Swain in Gilbert 1887:57. Type locality: North River, tributary of Black Warrior River, near Tuscaloosa , Alabama.

Lectotype. North River. Alabama. USNM 36695 , 32 mm SL, North River, Tuscaloosa , Alabama.

Paralectotypes. USNM 188971 , (17, 22–33).

Etheostoma rupestre was described from the North River by Gilbert and Swain ( Gilbert 1887). Additional diagnostic and descriptive characteristics are provided in Tsai (1968) and Boschung & Mayden (2004). The following diagnosis and description are based on characteristics provided by these sources as well as our own measurements.

Diagnosis. A species of clade Neoetheostoma (sensu Near et al. 2011) That differs from all other Etheostoma by the following combination of characteristics: 3–9 distinct lateral blotches (blotch shape includes diffuse irregular lines, clusters of dots, square markings, grouped sets of 1–3 vertical lines, and/or W -shaped tessellations), six dorsal saddles, and offset rows of stippling on the pectoral fins. Male nuptial coloration green (tends towards blue in pre-spawn individuals), diffuse black medial band in first dorsal fin with a green distal band, thick green medial band in second dorsal fin, diffuse green bars on side that usually encompass lateral blotches, anal fin infused with green, pelvic fins green usually with a transparent margin, caudal fin with dorsal and ventral edges colored in green occasionally forming thick green margin on posterior of caudal fin, nuptial color often present on anterior portion of head on mouth bleeding into branchiostegal membranes. Closely related congeners include the Etheostoma blennioides (Rafinesque) species complex + E. gutselli (Hildebrand) , E. zonale (Cope) , E. lynceum (Hay) , and E. histrio Jordan and Gilbert. Etheostoma rupestre differs from species in the E. blennioides complex by lacking a sheathed premaxilla, red nuptial coloration, and often-interconnected rows of U -shaped markings on the side. It differs from E. zonale and E. lynceum by possessing large lateral blotches, lacking red nuptial coloration, and by possessing fewer and less distinct vertical nuptial bars. It differs from E. histrio (the only one of these species with which it occurs sympatrically) by possessing a series a black or burgundy irregular lateral blotches and by lacking mottling on the underside of the head and lacking red in fin nuptial coloration.

Description. A large species of Etheostoma that attains a maximum size of 71 mm SL. Body elongate and cylindrical, slightly compressed, anterior portion of head highly convex, distinct frenum present, eyes large, ovalshaped, and high-set. Paired fins large. Dorsum coloration brassy or olive, ventral surface light olive, 3–9 lateral blotches along the midline (variable in shape and degree of separation) that range 3.8–8.2% of SL in average width and 2.8–7.5% of SL in average spacing, six dorsal saddles (highly variable in width, 5.7–9.1% of SL), numerous small dorsolateral dots or tessellations, suborbital and lacrimal bars present. Male nuptial coloration dark green to turquoise, distal band in the first dorsal fin 21.4–51.1% of dorsal-fin depth, total pigment (distal + medial band) depth 49.2–78.0% of dorsal-fin depth. Female genital papilla long and tubular, flattened distally, male genital papilla short and pointed. Lateral scale rows 39–65 (45–64>99% of the time), scales above the lateral line 4–7, scales below the lateral line 6–12, scales around the caudal peduncle 16–23, dorsal-fin spines IX–XII (>99% X–XII) rays 9–13, anal-fin spines 2, anal-fin rays 5–9, nape squamation naked to fully scaled (0–100%), belly squamation 10–90%, vertebrae 36–40.

Distribution. Etheostoma rupestre is endemic to the Mobile Basin in Mississippi, Alabama, Georgia, and Tennessee. In the Tombigbee River drainage, it occurs from ~40 air-km north of the Tombigbee-Alabama River confluence and extends north to the Black Warrior drainage and northeast Mississippi. In the Alabama and Cahaba River Basins it occurs from ~40 air-km north of the Tombigbee-Alabama River confluence north to the headwaters of the Cahaba River in Central Alabama. E. rupestre also occurs sporadically in several disjunct populations in the Coosa and Tallapoosa watersheds—namely in the Uphapee Creek and Hatchet Creek systems in east Alabama, and the Etowah, Talking Rock Creek (Coosawattee), and Conasauga systems in northwest Georgia and extreme southeastern Tennessee. The disjunct range and geographic variation in E. rupestre are discussed in the subspecies descriptions that follow.

Ecology. Etheostoma rupestre typically inhabits fast riffles and runs of large creeks and rivers above gravel and small cobble ( Kuehne & Barbour 1983). Previous authors have speculated that the spawning season of E. rupestre lasts from mid-March to April or May ( Joachim et al. 2003; Boschung & Mayden 2004). However, in lower Hatchet Creek male E. rupestre have been observed in peak nuptial coloration in mid-February (J. Dattilo, Alabama Division of Wildlife and Freshwater Fisheries, pers. comm.). Males in peak nuptial coloration and gravid females that appeared ready to spawn were collected from Caffee Creek (Cahaba drainage) on 22 March 2022. Male E. rupestre collected from Opintlocco Creek (Uphapee system) on 17 May 2022 had nuptial coloration that had nearly completely receded. We assume that the spawning season of E. rupestre ranges from mid-February to early April based on our anecdotal observations. Fecundity ranges from 18– 94 eggs /female ( Joachim et al. 2003). The morphology of the female genital papilla suggests that E. rupestre is an egg-attacher—a strategy common to other Neoetheostoma darters ( Page 1983). A life history study that incorporates populations from all subspecies is needed.

Etymology. From the Latin rupestris meaning living on rocks.

Figures

FIGURE 8. Male pigmentation of A) Etheostoma rupestre rupestre—47 mm SL, Cottondale Creek, County Road 32, Tuscaloosa, Alabama (photo by K. Boone), B) E. r. piersoni—61 mm SL, Chilatchee Creek, Highway 5, 1 mile north of Alberta, Alabama (photo by K. Boone), and C) E. r. uphapeense—45 mm SL, Opintlocco Creek, County Highway 20, ~3 miles East of Tuskegee, Alabama (Photo by B. Hilburn).