David J. Eisenhour

Declining Status of Two Species of the Macrhybopsis aestivalis Complex (Teleostei: Cyprinidae) in the Arkansas River Basin and Related Effects of Reservoirs as Barriers to Dispersal

From 1991 to 1997, we made 323 seine collections at 187 sites to determine the distributional status of two species of the Macrhybopsis aestivalis complex, M. tetranema (Gilbert) and M. hyostoma (Gilbert), in the Arkansas River Basin. A total of 545 M. hyostoma and 112 M. tetranema were taken in 39 collecting visits to 30 sites. Our survey indicated that the endemic M. tetranema has been extirpated from about 90% of its historic range, whereas the more widespread M. hyostoma has been extirpated from about 55% of its former range in the basin. Approximate year of extirpation for six populations of M. hyostoma in major stream segments was significantly correlated with year-of-completion for reservoirs that would have prevented recolonization from existing populations. This is consistent with the hypothesis that extirpations resulted from disruption of previously existing source/sink relationships among populations. No such correlation was detected for extirpations of seven populations of M. tetranema. This result would be expected from the metapopulation model in which the now-extirpated populations of M. tetranema were self-sustaining except during unusually harsh conditions (e.g., droughts). This factor apparently explains recolonization of the Cimarron River by M. hyostoma subsequent to extirpation of both species of Macrhybopsis from this river. The recolonization was delayed by about 25 years, apparently because of reservoir habitat between the Cimarron River and the other major stream draining into the reservoir, the upper Arkansas River, where there was a persistent population of the species.

Systematics of Macrhybopsis tetranema (Cypriniformes: Cyprinidae)

Morphometry, meristic features, pigmentation, and tuberculation were examined from 632 specimens of the Macrhybopsis aestivalis complex from the Arkansas River basin. Patterns of morphological variation support the recognition of two species in the basin: M. hyostoma in the middle and lower portions of the basin in Arkansas, Kansas, and Oklahoma; and M. tetranema in the middle and upper portions of the basin in Colorado, Kansas, New Mexico, Oklahoma, and Texas. Macrhybopsis tetranema is redescribed and compared to M. hyostoma, from which it can be distinguished by longer barbels, smaller eyes, smaller scales, reduced belly squamation, thicker lips, more conical head, and biserial pectoral fin tuberculation. These species are sympatric and maintain their identities in the Cimarron, Salt Fork of Arkansas, and Arkansas Rivers. Morphological intermediacy of M. tetranema in some areas of sympatry may reflect convergent adaptation to local conditions or hybridization with M. hyostoma. THE rivers of the western half of the Arkansas River Basin support cyprinids adapted

Two New Species of Noturus (Siluriformes: Ictaluridae) from the Tennessee River Drainage: Description, Distribution, and Conservation Status

Abstract Nominotypical Noturus elegans are herein restricted to the Green River drainage of central Kentucky and north-central Tennessee. Ten specimens and additional new material from the Duck River originally allocated to N. elegans are here described as a new species, Noturus fasciatus, restricted to the Duck River system and two minor tributaries of the lower arm of the Tennessee River, Tennessee. A second new species, Noturus crypticus, is described from the only known extant population in Little Chucky Creek, Greene County, Tennessee. These three taxa are closely related and are distinguished on the basis of modal differences in anal-fin ray numbers, body shape, pigmentation, and genotypic arrays. Noturus crypticus is described from only eight specimens, is clearly uncommon, probably relict, and in need of federal protection and future propagation efforts. All three species are primarily riffle/glide dwellers in small- to medium-sized streams where they may be found in or under gravel, rubble, and slab rock. The limited geographic distributions of the two new species places them at greater risk of extinction, warranting comprehensive evaluation of their life histories, demographic characteristics, recruitment rates, and nesting requirements.

Systematics of Etheostoma camurum and E. chlorobranchium (Osteichthyes: Percidae) in the Tennessee and Cumberland River Drainages with Analysis of Hybridization in the Nolichucky River System

The taxonomic relationship of Etheostoma camurum and E. chlorobranchium (Osteichthyes: Percidae) has remained unclear because of their morphological similarity and, prior to this study, the lack of any known area of contact. Taxonomically problematic populations from the Cumberland and Tennessee drainages were analyzed using informative meristic characters and nuptial coloration of males. Data from these analyses indicate that the population in the Hiwassee River is assignable to E. camurum, and populations in the Pigeon River and Abrams Creek are assignable to E. chlorobranchium. During the summer of 1991, an area of the Nolichucky River in Unicoi County, Tennessee, was found that apparently contained both E. chlorobranchium and E. camurum. This contact area contained nuptial males with coloration intermediate between that of either species, putative hybrids, along with nuptial males of each of the parental color types. Limited hybridization in this area is also supported by morphometric and informative meristic data. Allozyme analysis demonstrates more extensive hybridization in the area of contact than do morphometric data but limited introgression of alleles outside of the contact zone. Despite the apparent hybridization that exists in the zone of contact, the gene pools of each species appear to be effectively isolated, and parental phenotypes of both species are found throughout the zone, suggesting that E. camurum and E. chlorobranchium should continue to be regarded as distinct species.

Genetic Variation in Western Members of the Macrhybopsis aestivalis Complex (Teleostei: Cyprinidae), with Emphasis on Those of the Red and Arkansas River Basins

Abstract We used protein electrophoresis of the allozyme products of 21 gene loci to examine relationships among five western species of the Macrhybopsis aestivalis complex (sensu Eisenhour, 1997), with emphasis on three species recognized from morphology in the Red and Arkansas river basins. Monophyly was supported for both species endemic to those basins, M. australis in the Red and M. tetranema, in the Arkansas. However, support was weak because of high genetic similarity between these species and the more wide-ranging species, M. hyostoma. Within the Arkansas and Red river basins, only 2% and 5%, respectively, of total genic diversity was attributable to differences between the endemic species and M. hyostoma. Across all samples from the two basins, only 14% of total diversity was attributable to among-species differences. Phenetic and allele-frequency parsimony analyses grouped M. hyostoma from the Red and Arkansas river basins with the associated endemic in the respective basin rather than with populations of M. hyostoma from elsewhere. The results are consistent with the indication from morphology that M. tetranema and M. australis are sister species, if it is assumed that the present patterns of allozyme variation are a result of subsequent contact and introgressive hybridization with M. hyostoma. Collections of M. aestivalis from the Rio Grande Basin and M. marconis from the San Marcos River Basin were markedly divergent from each other and from other members of the complex.

Morphological Variation and Systematics of the Notropis rubellus Complex in Kentucky and Tennessee

Abstract Samples of the Notropis rubellus complex were collected from 33 localities in Kentucky and Tennessee during the late spring and early summer of 1998–2001. Based on nuptial coloration, scale and fin-ray counts, and body shape, two taxa were diagnosed and recognized as species in the study area. Notropis rubellus (Agassiz) occupies upland streams of the Ohio River basin upstream of the mouth of the Green River and in the Cumberland River drainage above Cumberland Falls. Notropis micropteryx (Cope) occurs in upland streams of the Cumberland River drainage downstream of Cumberland Falls and the Tennessee River and Green River drainages. This species differs from N. rubellus in having modally fewer circumferential scales (23–24 vs. 25–26), modally fewer scales below the lateral line (three vs. four), and less red on the dorsum of the head of nuptial males. Green River populations exhibit more mean scales below the lateral line and slightly more intense red than other N. micropteryx populations. Support for recognition of these taxa as evolutionary species includes zoogeographic evidence in addition to the array of morphological characters.

Two New Intergeneric Hybrids Involving Semotilus atromaculatus and the Genus Phoxinus with Analysis of Additional Semotilus atromaculatus: Phoxinus Hybrids

Natural hybridization is relatively common among North American cyprinids (Schwartz, 1972, 1981), especially among species that spawn over the gravel nests of pit-, pit-ridge-, and mound-building cyprinids (Johnston and Page, 1992). A widespread pit-ridge-building cyprinid, the creek chub, Semotilus atromaculatus, is known to hybridize with a number of cyprinids (Schwartz, 1972, 1981). There are numerous reports of hybrids involving species of Phoxinus, including P oreas (Hambrick, 1977; Maurakis and Woolcott, 1992), P erythrogaster (Cross and Minckley, 1960; Greenfield et al., 1973; Grady and Cashner, 1988), and P eos and P neogaeus (New, 1962; Legendre, 1970). There are no previous reports, however, of a hybrid involving two recently described species, the Tennessee dace, P tennesseensis, or the blackside dace, P cumberlandensis.

Reproductive Biology of the Northern Madtom, Noturus stigmosus (Siluriformes: Ictaluridae) from the Licking River, Kentucky

Abstract The reproductive biology of the northern madtom, Noturus stigmosus Taylor, was examined in the Licking River, Bath and Rowan counties, Kentucky from 2001–2006. Gonadosomatic indices suggest a discrete spawning event in mid-summer, with sexual maturity reached at approximately 60 mm standard length (SL). Clutch size was estimated at 70–110 eggs per female based on examination of mature ovaries. Males and females come into reproductive condition in early summer and exhibit secondary sexual dimorphism typical of madtoms. Four nests were discovered in early to mid-July in water 23–25°C. All nests were in cavities under large slabrocks in a raceway with moderate current (0.36–0.69 m sec−2) above a large riffle. Nests contained 40–87 eggs or embryos; no guardian males were found with any nest. Eggs reared in the lab at 21–22°C hatched about 13 days after fertilization, which is the longest reported for madtoms. Embryonic and larval development were similar to those of other madtoms. Hatchlings were 8.1–9.3 mm total length (TL). By 10 days, the yolk sacs were absorbed, and young (now 15.4–15.7 mm TL) had acquired pigmentation diagnostic for the species. Approximately one month after hatching (at ∼20 mm SL), young moved downstream from the raceway into a large riffle.

Hybridization of Lythrurus fasciolaris and Lythrurus umbratilis (Cypriniformes: Cyprinidae) in the Ohio River Basin

Abstract The Scarlet Shiner (Lythrurus fasciolaris) and Redfin Shiner (L. umbratilis) are common small minnow species usually exhibiting a parapatric geographic distribution within the Ohio River basin. Historical collection records suggest several areas of possible syntopy along the periphery of distributional ranges, with suspected hybridization based upon observed intermediate morphology of nuptial males. Nuptial males from nine localities with suspected hybridization were collected in June and July 2004; morphometric, meristic, tuberculation, and coloration data were collected and analyzed to test the hypothesis that these species are hybridizing. Based on univariate and multivariate analyses and qualitative assessment of the morphological data, the Green River, Kentucky River, and Salt River drainages in Kentucky and the Scioto River drainage in Ohio all have populations with evidence of past gene flow. Comparisons of current observations with historical collections show an eastward range expansion of L. umbratilis with replacement of L. fasciolaris. The introgression of morphological characters toward those of L. umbratilis in the Green River, Salt River, and Scioto River drainages imply that hybridization may play a direct role in this range expansion. The novel morphology of specimens from Eagle Creek, Kentucky River drainage suggests that hybridization also has resulted in the development of a static, morphologically distinct hybrid swarm. In each case, environmental conditions seem closely linked with the occurrence and net effects of hybridization between these two species.

Clinal Variation in Ohio River Basin Populations of the Redfin Shiner (Lythrurus umbratilis)

Abstract Prior to this study, undocumented morphological variation in Lythrurus umbratilis (Redfin Shiner) has impaired identification of many samples of eastern populations of the species. Meristics, morphometrics, tuberculation, pigmentation, and nuptial male coloration of over 700 specimens of L. umbratilis were examined in order to assess patterns of geographic variation and species limits in the Ohio River basin. Principle component and spatial autocorrelation analyses of these data demonstrate that morphological variation in L. umbratilis is clinal along most of the length of the Ohio River basin. Specimens from eastern populations have less black in the dorsal fin of breeding males, have lower mean scale counts, and are more slender than western populations. The cline does not extend into central and northern Ohio, as populations have relatively high meristic counts and more robust males. These analyses suggest that recognition of an additional species in the Ohio River basin is not warranted at this time. The cline may reflect the influence of drainage evolution of the region, or even past gene flow with Lythrurus fasciolaris (Scarlet Shiner), a closely related species with a distribution parapatric to that of L. umbratilis.