Do River Drainage Boundaries Coincide with Phylogeographic Breaks in the Redband Darter?
The Redband Darter,
Etheostoma luteovinctum
, is a benthic headwater fish species found in the Caney Fork and Stones rivers (Cumberland River) and the Duck and Elk rivers (Tennessee River) of central Tennessee. Phylogenetic analyses of 2601 amplified fragment length polymorphisms (AFLPs) were used to assess the relationships among populations and identified two genetically distinct lineages of Redband Darter. One lineage is comprised of populations in the Duck R., Elk R., Middle Fork Stones R., West Fork Stones R., and Hickory Creek of the Caney Fork River, while the other lineage is confined to the remainder of the known localities in the Cumberland R. drainage. As clades were not restricted to drainage or system boundaries, patterns suggest system and drainage transfers. Additionally, morphological variation was examined among populations using standard meristic data and nuptial male color and pigmentation characteristics. Although some morphological traits varied between the two clades, members were not clearly diagnosable using morphology. Taxonomic recognition is not proposed for the two identified clades; however, each clade should be recognized as an evolutionarily significant unit and regarded as such in future conservation efforts. Furthermore, this study demonstrates the utility of AFLPs to assess genetic variation and phylogenetic relationships for species-level taxonomic or phylogeographic studies.
Localities examined for assessment of morphological and genetic variation in Etheostoma luteovinctum. Shaded areas encompass the known range of the species in each system and represent the two clades recovered by the maximum parsimony analysis of 2601 amplified fragment length polymorphism loci. Clade A contained study sites 1–13 representing the East Fork Stones and Lower Stones River, Lower Caney Fork River, North Prong Barren Fork of the Caney Fork River, and Cumberland River tributaries. Clade B contained study sites 14–27 representing the Elk River, West and Middle Fork Stones River, Duck River, and Hickory Creek of the Caney Fork River.
Maximum-parsimony phylogram of Etheostoma luteovinctum based on 2601 amplified fragment length polymorphism characters. Values on nodes are bootstrap values from parsimony analyses followed by those from Nei-Li distance analyses in parentheses. An asterisk (*) indicates a node was not recovered in the distance analysis. Individuals are numbered by site number, which corresponds to those in Figure 1. Numbers in parentheses following site numbers are the number of individuals.
Plot of principal component factor scores for ten meristic characters on PC axes 1 and 2 for Etheostoma luteovinctum. Polygons bound all individuals examined from a given drainage, system, river, or stream and include: (1) Eaton Creek (site 2), Lower (site 4) and East Fork (sites 7, 9, and 11) Stones River, 33 specimens; (2) Barren Fork-Upper Caney Fork River (sites 12 and 13), 17 specimens; (3) Duck River (sites 15, 21, 23, 24, 25), 39 specimens; (4) Middle (site 18) and West Fork (site 19) Stones River, 19 specimens; (5) Marshall Creek-Lower Caney Fork River (site 8), 10 specimens; (6) Hickory Creek-Upper Caney Fork River (UT 91.2518), 10 specimens; (7) Elk River (site 27), 12 specimens. Table 2 lists component loadings for meristic characters.
Plot of principal component factor scores for ten meristic characters on PC axes 1 and 2 for Etheostoma luteovinctum. Polygons bound all individuals examined from a given clade (see Figs. 1, 2) and include: (1) Clade A, 70 specimens; (2) Clade B, 80 specimens. Table 2 lists component loadings for meristic characters.
Contributor Notes
Associate Editor: T. J. Near.