Macrhybopsis etnieri Gilbert & Mayden

Gilbert, Carter R., Mayden, Richard L. & Powers, Steven L., 2017, Morphological and genetic evolution in eastern populations of the Macrhybopsis aestivalis complex (Cypriniformes: Cyprinidae), with the descriptions of four new species, Zootaxa 4247 (5), pp. 501-555 : 514-517

Macrhybopsis etnieri Gilbert & Mayden sp. nov.

Coosa Chub

Figs. 1 C, 2; Table 1

Hybopsis hyostomus .— Gilbert 1891: 155, 157 (in part; record from Oxford, Alabama). Scott 1951: 36–37 (summary of fish sampling from Coosa River, near Childersburg Alabama; reference to “ Nocomis hyostomus ” believed to refer to Macrhybopsis etnieri ).

Hybopsis aestivalis .— Smith-Vaniz 1968: 40 (in part; general account; Alabama). Dahlberg & Scott 1971: 16, 59 (Georgia records). Stiles & Etnier 1971: 14 –16 (annotated list of fishes from Conasauga River system, Tennessee and Georgia). Yerger 1978: 12 –13 (photograph of specimen from Cahaba River; account refers to Florida populations of Macrhybopsis pallida ). Wallace 1980: 180 (in part; brief account; distribution map of M. aestivalis complex).

Extrarius sp. cf. aestivalis .— Boschung 1989: 50 (diagnostic characters distinguishing it from other undescribed congener in Mobile Bay basin).

Macrhybopsis aestivalis .— Boschung 1992: 52 (in part; partial synonymy for Alabama; general account). Etnier & Starnes 1994: 192 –194, pl. 59 (in part; general account; morphological variation; localities mapped for Conasauga River in Tennessee). Mettee et al. 1996: 218 –219 (in part; general account; localities mapped for entire M. aestivalis complex in Alabama and from Mobile Bay basin in Georgia).

Macrhybopsis sp. cf. M. aestivalis “B”— Boschung & Mayden 2004: 208 –209; plate 21B (characters; relationships; distribution; spot-distribution map for Alabama [in part]; colored illustration).

Holotype. UF 90100 (female, 52.2 mm SL), from Etowah River , just off county road 76, 8.6 air km SE of center of Dawsonville, Dawson County, Georgia; Noel M. Burkhead and crew (field no. NMB 1281 ), 19 November 1991.

Paratypes. The following paratypes, comprising 71 lots and 513 total specimens, are listed in abbreviated fashion by state, river system, and county, followed by museum catalogue number and numbers of specimens. Complete locality data appear in Appendix 1.

Catalogue numbers accompanied by an asterisk (*) denote lots originally containing specimens of both Macrhybopsis etnieri and M. boschungi , where the species were sampled syntopically.

Alabama: Cahaba River : (Bibb Co.) UF 15434 (4)* [ex UAIC 1611.03 ], UF 116298 (12) ; UAIC 1611.03 (24)* [see UF 15434], UAIC 2029.04 (2), UAIC 4679.04 (1), UAIC 5584.01 (2), UAIC 6452.01 (12), UAIC 6788.03 (4), UAIC 6789.03 (36), UAIC 6797.03 (2), UAIC 7186.03 (9), UAIC 7187.03 (25), UAIC 7198.02 (7)*, UAIC 7702.03 (4), UAIC 11053.01 (1 [illustrated female specimen from Boschung & Mayden 2004: pl. 21B; present fig. 1C]); UMMZ 250266 (formerly UMMZ 171750) (28)*; INHS 76341 (5), INHS 76335 (3); (Perry Co.) UF 116294 (6) ; UAIC 6791.03 (18)*, UAIC 6798.03 (6), UAIC 6799.02 (7)*, UAIC 7191.03 (3), UAIC 7194.03 (10)*, UAIC 7197.02 (6), UAIC 7199.03 (4)*.

Tallapoosa River : (Chambers Co.) UF 116299 (6); (Lee Co.) UMMZ 111192 (1) , UMMZ 111193 (5), UMMZ 111194 (12), UMMZ 142909 (1); (Randolph Co.) UT 44.2293 (3); ( Tallapoosa Co. ) UF 91617 (1); UT 44.2300 (1) ; UAIC 1040.03 (13).

Georgia: Coosa River: (Cherokee Co.) UF 86141 (3), UF 86274 (1), UF 86289 (12), UF 91296 (17), UF 91414 (1); UT 44.1891 (9), UT 44.1926 (6), UT 44.1937 (13), UT 44.1942 (3), UT 44.2230 (6), UT 44.2240 (2); (Dawson Co.) UF 15785 (2), UF 86162 (9), UF 86182 (1), UF 86203 (3), UF 86227 (9), UF 97284 (30), UF 237855 [ex UF 90100] (14 paratopotypes); UT 44.1934 (6); UMMZ 175589 (1); (Forsyth Co.) UF 86244 (59 originally, now 34), USNM 437193 (5), ANSP 200788 (5), MCZ 171825 (5), TU 204137 (5), KU 41377 (5) (preceding five series ex UF 86244); (Lumpkin Co.) UF 90116 (3).

Tallapoosa River: (Haralson Co.) UT 44.2794 (1).

Tennessee: Coosa River: (Bradley Co.) UF 42694 (1), UF 42743 (1); UT 44.303 (1), UT 44.484 (2), UT 44.1692 (2); ( Polk Co. ) UT 44.400 (1), UT 44.413 (11); USNM 230851 (1).

Diagnosis. A species of the Macrhybopsis aestivalis complex, as defined in the generic diagnosis. Distinguished from all other members in the complex in having 1,4–4,1 pharyngeal teeth; anal opening situated midway between pelvic and anal-fin origins (vs. 70 percent of distance in all other congeners except Macrhybopsis pallida ); origin of dorsal fin situated distinctly posterior to imaginary line extending upward from pelvic-fin origins; belly anterior to pelvic fins usually with a complete bridge of scales (two to five scales deep), the bridge mostly obscured by overlying epidermal tissue about 20 percent of the time.

Other important diagnostic features include a single pair of short maxillary barbels; eight anal rays; upper twothirds of body strongly pigmented with relatively large and prominent melanophores, interspersed with smaller melanophores ( Fig. 1 C); pectoral fins in both sexes short and moderately to strongly rounded, seldom if ever extending posterior to pelvic-fin origin; snout short and rounded, its length slightly longer than diameter of eye; tubercles on pectoral fins of nuptial males relatively well defined only in first row, those tubercles in subsequent rows tiny and poorly defined but apparently uniserial; genital papillae well developed.

Description.—Characters listed in the diagnosis are not repeated here, unless additional clarification is required. Variation in meristic characters is presented in Table 1.

Dorsal-fin rays 8; anal-fin rays 8, rarely 7; pectoral-fin rays usually 14–15 (range 12–15); pelvic-fin rays usually 8 (range 7–9); lateral-line scales usually 36–38 (occasionally 39); predorsal scales irregularly distributed and poorly defined, numbering 15–17 (rarely 18 or 19); body-circumferential scale rows above and between lateral lines on either side of body 9 to 11 (occasionally 12); body-circumferential scale rows below and between lateral lines on either side of body usually 10–12 (range 9–13); total caudal-peduncle scale rows uniformly 12 (five rows above and below lateral lines on either side of body); total vertebrae usually 38 (range 37–39), these averaging higher (often 39) in upper areas of Coosa River drainage in Georgia and Tennessee; pharyngeal teeth usually 1,4- 4,1, the lesser tooth occasionally absent from one or both sides of pharyngeal arch; pharyngeal teeth short, thin, and hooked, with little or no grinding surface; anal and dorsal fins bluntly pointed to slightly falcate; head moderately rounded and moderately flattened ventrally; mouth inferior and horizontal, not as wide as head; lips moderately fleshy, not thickened posteriorly; eyes round and relatively small, their diameters slightly less than pre-orbital distance; pre-orbital and post-orbital distances approximately equal; four or five rudimentary gill rakers on upper limb of outer (anteriormost) gill arch, the rakers usually absent from lower limb of arch.

Specimens in life without chromatic pigmentation; translucent pale green or gray dorsally and silvery white ventrally; predorsal streak thin but usually present; postdorsal streak absent; thin line of pigment often present along margin of dorsolateral scales and sometimes on ventrolateral scales; lateral stripe on caudal peduncle poorly defined, fading anteriorly.

Females attain a larger size than males, the largest female (the holotype) examined 52.2 mm SL (UF 90100) from Etowah River , Dawson County, Georgia ; the largest male examined 45.0 mm SL (UF 15434) from Cahaba River , Bibb County, Alabama .

Comments. Macrhybopsis etnieri is one of the most morphologically distinctive members of the M. aestivalis complex ( Fig. 1 C), most notably in having a unique pharyngeal-tooth count (usually 1,4-4,1), intermediate position of anus relative to pelvic and anal-fin origins, more posterior position of the dorsal fin relative to the pelvic fins, and very small nuptial tubercles on pectoral-fin rays of breeding males.

Macrhybopsis etnieri shares, with M. pallida , two characters unique to members of the M. aestivalis complex, namely an intermediate position of the anus relative to the origins of the pelvic and anal fins (versus over twothirds of distance in other species), and well developed genital papillae (versus papillae lacking or extremely reduced). Eisenhour (2004: figs. 16–17) hypothesized a close relationship between the two species, presumably based largely on these two characters. Their respective geographic distributions raise doubts as to this proposed relationship, since biogeographically their ranges are quite disjunct and this relationship is not duplicated by any other known closely related pairs of fish species. This hypothesis also is not supported by genetic data presented in the present paper, which, in combination with the phylogenetic tree generated via Generalized Parsimony, shows M. pallida to have a very close relationship to the geographically adjacent, but morphologically dissimilar, M. boschungi . M. etnieri , in turn, appears to have a sister relationship to all remaining members of the M. aestivalis complex (see discussion on Relationships and Historical Biogeography).

Distribution. Macrhybopsis etnieri is restricted to upper sections of the Mobile Bay basin, above the Fall Line, including the Cahaba, Coosa and Tallapoosa river systems, in Alabama, northwestern Georgia, and extreme southeastern Tennessee ( Fig. 2 ). It is replaced below the Fall Line by Macrhybopsis boschungi , to which it is not intimately related but with which it occurs sympatrically (or syntopically) in an approximately 40-km section of the middle Cahaba River system in central Alabama ( Fig. 2 ). More detailed distributional information appears below.

Habitat. Macrhybopsis etnieri occurs in clear, moderately large flowing streams with a sand, gravel, or fine rubble bottom above the Fall Line in the Cahaba, Coosa and Tallapoosa river systems of Alabama, Georgia, and Tennessee . Collections are largely concentrated in three areas: the Etowah River ( upper Coosa drainage) in northwestern Georgia ; Hatchet Creek , in Coosa and Clay counties, Alabama ; and the middle Cahaba River south of Birmingham , Alabama . Other collections are known from scattered localities, including the Choccolocco Creek watershed in Cleburne and Talladega counties, Alabama ; the Tallapoosa River system of eastern Alabama and western Georgia ; and the Conasauga River ( upper Coosa drainage) in Tennnessee and Georgia . A large collection from the Coosa River , at Childersburg, Alabama, from which no voucher specimens appear to have been retained and which thus cannot be firmly documented ( Scott 1951), is discussed below.

The comparatively large number of records for the Cahaba and Etowah systems, and from the Hatchet Creek watershed, is partly attributable to the heavier concentrations of fish collections from these three areas. The Cahaba River is in close proximity to Tuscaloosa, and has been sampled frequently over the years by ichthyologists from the University of Alabama ; Hatchet Creek was visited frequently from 1978–1985 by personnel from nearby Auburn University; and the Etowah River was the focus of directed studies by personnel with the U.S. Geological Service, in Gainesville, Florida, from 1990–1994.

Since the Coosa River drainage in Alabama has been well sampled for fishes throughout the years, probably totaling over 700 collections ( Boschung 1961; Mettee et al. 1996: 18; Boschung & Mayden 2004: 71, fig. 6.1), the scattered distribution and overall paucity of records of the Coosa Chub seems strange. One possible explanation is that populations of this species were once concentrated in the Coosa River proper, but have now disappeared following conversion of the Alabama portion of the river to a series of reservoirs ( Boschung & Mayden 2004: 21). This hypothesis receives support from Scott (1951), who summarized results of a major pre-impoundment fisheries investigation, during July and August, 1949, of the Coosa River near Childersburg, in Talladega County. A wide variety of collecting techniques were employed, with smaller individuals being collected mostly with fish traps and liberal applications of rotenone. Heavy emphasis was placed on the larger and economically more important fishes, as evidenced from the summary table on page 37 of Scott’s paper. Only three minnows were listed, which undoubtedly is a gross underrepresentation, given that at least 24 cyprinid species are known to occur in this portion of the Coosa River and its major tributaries ( Boschung 1961; Mettee et al. 1996; Boschung & Mayden 2004). Surprisingly, one of the three cyprinids listed by Scott (1951: 37, table 6) was Nocomis hyostomus (referred to simply by the vernacular name “Chub”), which, based on site of collection (well above the Fall Line), almost certainly represents the species now recognized as Macrhybopsis etnieri . It is also significant that this species was indicated as being the most numerically dominant cyprinid encountered during the Childersburg operation. Unfortunately, no voucher specimens were apparently saved that would serve to provide positive verification.

A survey of museum fish collections has revealed only 13 confirmed Alabama collections of Macrhybopsis etnieri from the Alabama portion of the Coosa drainage, all housed at Auburn University (see Appendix 1 for detailed information). Of these, 11 are from Hatchet Creek, in Coosa and Clay counties, and the remaining two are from the Choccolocco Creek watershed in Talladega and Cleburne counties (see maps in Mettee et al. [1996: 218] and Boschung & Mayden [2004: 208]). Presence of M. etnieri at those localities may best be explained by those creeks’ relatively large size, coupled with absence of dramatic alteration from large urban areas upstream.

The situation described for Alabama may be mirrored in Georgia as well. Considering the concentration of recent records from the Etowah River system in Georgia, it is noteworthy that Macrhybopsis etnieri appears not to have been encountered by David Starr Jordan in any of his collections from the upper Coosa drainage in that state ( Jordan 1877; Jordan & Brayton 1878), none of which were from the Coosa River proper. From those authors’ detailed descriptions of the streams sampled (most notably Silver and Rocky creeks, tributaries to the Etowah and Oostanaula rivers, respectively), the habitats sampled would appear entirely suitable for Macrhybopsis etnieri . The only other cyprinid species known from this region possessing a terminal maxillary barbel are Rhinichthys cf atratulus (confined to small streams), Macrhybopsis s toreriana (a rare inhabitant of the mainstem Coosa River) ( Mettee et al. 1996: 220), and Hybopsis lineapunctata . The last, which is the species most likely to be confused with M. etnieri , was reported by Jordan (1877: 328–330) under the name Nocomis amblops var. winchelli , and by Jordan & Brayton (1878: 53) as Ceratichthys winchelli . Hybopsis lineapunctata was described by Clemmer & Suttkus (1971), at which time all known pertinent material from the early Jordan collections was examined. Had any specimens of M. etnieri been present, they undoubtedly would have been noted. Likewise, no specimens were found among recently discovered remnants of the Jordan collections that had lain undetected at Butler University for well over a century, and which were analyzed by Gilbert (2009).

Based on the above evidence, it seems reasonable to conclude that M. etnieri has never been particularly common or uniformly distributed throughout the Coosa River basin.

Distributional interaction with Macrhybopsis boschungi . Macrhybopsis etnieri occurs sympatrically (or syntopically) with M. boschungi over an approximately 40-km section (airline distance) of the middle Cahaba River, from Sprott, in Perry County, upstream to about 10 km northeast of Centreville, in Bibb County. No samples of Macrhybopsis are known from farther upstream ( Mettee et al. 1996: 218; Boschung & Mayden 2004: 208), although many fish collections have been obtained from upper reaches of the Cahaba River in Jefferson, Shelby, and St. Clair counties ( Boschung & Mayden 2004: 71). The eight mixed collections available for study were taken from late May to early October during the years 1956–1984. None of these collections had individuals that were morphologically intermediate between M. boschungi and M. etnieri . In seven of the eight samples M. etnieri was the dominant form, collectively totaling 92 specimens compared to only 13 M. boschungi. The remaining mixed lot of 30 specimens included 20 M. boschungi.

Sixteen lots of fishes from within the zone of overlap in the Cahaba River comprised only M. etnieri . These varied in size from one to 39 specimens, with most (twelve of sixteen) including fewer than ten individuals. Six additional lots (all small) included only M. boschungi , each comprising from one to five specimens. To summarize, a total of 239 specimens of M. etnieri and 43 specimens of M. boschungi were included in collections from the middle Cahaba River in Bibb and Perry counties. This contrasts with the three lower Cahaba River collections from Dallas County (all west of Selma, about 29 air km south of the Sprott locality in Perry County), which comprise homogenous assemblages (total of 159 specimens) of M. boschungi .

Several conclusions can be drawn from the above. First, although the Fall Line provides a precise distributional separation for the two Mobile Basin species of Macrhybopsis in the Coosa and Tallapoosa drainages, this break is notably less sharp in the Cahaba River. Second, there is no evidence of gene interchange in any of the mixed samples from the last drainage. Third, within the area of sympatry M. etnieri appears to be the dominant form numerically, by a factor of around five to one. Fourth, there appears to be no obvious seasonal separation of the two species within the area of sympatry, mixed collections having been taken during May and June and from August to October. Although the absence of July samples might at first appear meaningful, it should be noted that only two very small samples (total of three specimens) were available from that month. Fifth, upstream distributions of both species in the Cahaba River appear to stop abruptly about 10 km northeast of Centreville. Finally, a complete distributional break between the two species in the Cahaba River occurs somewhere within the 29-km stretch between Sprott and Selma.

Conservation Status. Macrhybopsis etnieri has not been accorded any conservation status, probably because it has remained undescribed. Its scattered occurrence in several widely separated parts of the Coosa and Tallapoosa river systems is most likely a function of habitat preference. Other than the presumed collections by Scott (1951) in the mainsteam Coosa River, and three from Hatchet Creek in Coosa County, Alabama (AUM nos. 35067, 41781 and 58687), totaling 125, 43, and 37 specimens, respectively, all samples are of small to moderate size, with the vast majority comprising fewer than ten individuals. Although the species does not appear to be under any immediate threat, populations should continue to be monitored regularly.

Etymology. Named for Dr. David A. Etnier, Emeritus Professor of Zoology at the University of Tennessee, for his many contributions to southeastern ichthyology and aquatic biology, including co-authorship of the definitive book on the fishes of Tennessee.

Figures

FIGURE 1. Species of Macrhybopsis aestivalis species complex from eastern North America. A) Macrhybopsis hyostoma, UAIC 11060.03, Female, 34 mm SL, Alabama, Limestone County, Elk River, 28 September 1994. B) Macrhybopsis boschungi, UAIC 10845.03, Female, 50 mm SL, Alabama, Dallas County, Cahaba River, 12 July 1993. C) Macrhybopsis etnieri, UAIC 11053.01, Female, 44 mm SL, Alabama, Bibb County, Cahaba River, 24 June 1994. D) Macrhybopsis pallida, UAIC 10855.04, Female, 36 mm SL, Alabama, Escambia County, Conecuh River, 15 July 1993. E) Macrhybopsis tomellerii, UAIC 11364.03, Female, 51 mm SL, Mississippi, Covington County, Pascagoula River drainage, 18 February 1994.

FIGURE 2. Distribution of southeastern species of Macrhybopsis east of the Mississippi River. Individual species are identified by symbol and color. Circles with half blue and half red represent locations where M. boschungi and M. etnieri occur syntopically.