Systematics of the Stripetail Darter, Etheostoma kennicotti (Putnam), and the Distinctiveness of the Upper Cumberland Endemic Etheostoma cumberlandicum Jordan and Swain
The Stripetail Darter, Etheostoma kennicotti (Putnam), is widely distributed in tributaries of the lower Ohio River, the upper Green River system, the Clarks River system, throughout the Tennessee River system, the Laurel River system, and the upper Cumberland River system. Etheostoma cumberlandicum Jordan and Swain was described in 1883 from a population sampled in the Clear Fork system that drains to the upper Cumberland. A previous morphological analysis led to the placement of E. cumberlandicum into the synonymy of E. kennicotti. Results from molecular phylogenetic and relaxed molecular clock analyses, genetic variation at 25 microsatellite loci, morphological disparity in meristic traits, and variation in pigmentation from specimens sampled throughout the geographic distribution of E. kennicotti (s.l.) indicate E. cumberlandicum is a distinct species and there are multiple undescribed species masquerading as E. kennicotti. We elevate Etheostoma cumberlandicum out of synonymy and propose Moonbow Darter as the common name for the species. The results of the phylogenetic analyses are discussed in the context of the historical biogeography of rivers draining the Eastern Highlands of North America.
Geographic distribution of Etheostoma kennicotti sensu lato and Etheostoma cumberlandicum and sampling locations of specimens used in molecular and morphological analyses. The populations in the Green River system, the Laurel River system, and the Tennessee River system (partitioned between lower and upper Tennessee River) are each considered undescribed species currently listed as E. kennicotti.
Phylogenies of Etheostoma kennicotti sensu lato and Etheostoma cumberlandicum inferred from the mitochondrial cytb gene. (A) Bayesian inferred cytb gene tree. Bayesian posterior probabilities are indicated with filled circles. (B) Maximum clade credibility chronogram of Etheostoma kennicotti sensu lato and Etheostoma cumberlandicum. Bars indicate 95% posterior density of age estimates at nodes in the phylogeny.
Population structure inferred from 25 microsatellite loci. (A) Hierarchical STRUCTURE analysis identifies 18 genetic clusters (K). Optimal K values for each round of hierarchical clustering are shown. (B) STRUCTURE results for K = 6. Pie charts represent average ancestry coefficients for each sampling locality. The phylogeny is redrawn from Figure 2A.
Morphological disparity in Etheostoma kennicotti sensu lato and Etheostoma cumberlandicum. (A) Plot of first and second principal component scores of meristic traits in Etheostoma kennicotti sensu lato and Etheostoma cumberlandicum. (B) Mahalanobis distances of PC scores for contrasts of species in the Etheostoma kennicotti complex. In each comparison, the red and blue lineages on the cytb phylogeny are contrasted. A lineage that is a dashed branch is not included in the contrast. The comparison between the upper (U.) Tennessee and lower (L.) Tennessee River is considered an intraspecific contrast.
Photographs of live specimens of Etheostoma cumberlandicum, E. cf. kennicotti Laurel River, and E. kennicotti. (A) Etheostoma cumberlandicum, YPM ICH 028205, 62 mm SL, male, Wolf Creek, Whitley Co., Kentucky, USA, 28 April 2015. (B) Etheostoma cumberlandicum, YPM ICH 028204, 46 mm SL, female, Little Wolf Creek, Whitley Co., Kentucky, USA, 25 March 2015. (C) Etheostoma cf. kennicotti, Laurel River species, YPM ICH 028202, 63 mm SL, male, Lick Fork, Laurel Co., Kentucky, USA, 14 May 2015. (D) Etheostoma kennicotti, UF 167303, 61 mm SL, Bay Creek, Pope Co., Illinois, USA, 18 April 2007.
Contributor Notes
Associate Editor: M. P. Davis.