Thursday, April 18, 2013

New Darter Species from Tennessee’s Caney Fork River


A new species of fish only found in the state of Tennessee was scientifically described this month and was named after a co-author of The Fishes of Tennessee book. The new species was formerly considered an isolated population of the Bloodfin Darter Etheostoma (Nothonotus) sanguifluum, which is otherwise widespread in medium-sized creeks throughout the middle Cumberland River drainage in Kentucky and Tennessee.

The Bloodfin Darter, Etheostoma sanguifluum (or Nothonotus sanguifluus, see below) from the middle Cumberland River drainage in Kentucky and Tennessee. C) male and D) female. From figure 3 in Keck and Near 2013.
 
Ben Keck at the University of Tennessee and Tom Near at Yale University described the new species based on differences in male nuptial coloration and scale counts.  The new species is the Caney Fork Darter Nothonotus starnesi, restricted to the Caney Fork River system above Great Falls in Grundy, Van Buren, Warren, and White counties near McMinnville Tennessee. It is named after Wayne Starnes, co-author of the Fishes of Tennessee and Curator of Fishes at the North Carolina Museum of Natural History, for his contributions on the natural history and biology of North American freshwater fishes.
 
The Caney Fork Darter, Nothonotus starnesi, from the Caney Fork River system above Great Falls near McMinnville Tennessee Photo of nuptial male by Dave Neely.

The Caney Fork Darter, like many other darters, displays sexual dimorphism which is most pronounced during the breeding season (May-July), with males having bright red spots on their sides and red and blue in their fins. The species occupies fast-flowing riffles over large cobble and small boulders in medium to large streams. Most populations appear stable, but the Caney Fork Darter’s restricted range, impoundment of habitat by the Great Falls reservoir, and threats from intensive silviculture, livestock production, urbanization, and invasive species put this species at risk and may require future conservation efforts.
The Caney Fork Darter, Nothonotus starnesi, from the Caney Fork River system above Great Falls near McMinnville Tennessee E) male and F) female. From figure 3 in Keck and Near 2013




The taxonomy of the scientific names of the Bloodfin and Caney Fork darters and their close relatives is undergoing changes. These species, as well as some twenty other species, were previously placed in the subgenus Nothonotus within the genus Etheostoma (Etnier and Starnes 1993). Molecular studies based on a mitochondrial gene indicated that the subgenus was more closely related to other darter genera, leading Near and Keck (2005) to elevate Nothonotus to the generic level, which changed the ending on the specific epithet of many species to match the gender of the new genus (e.g. sanguifluum to sanguifluus).  Later molecular studies using nuclear genes in combination with mitochondrial genes (Near et al. 2011) or nuclear genes alone (Near and Keck 2013) showed that Nothonotus and Etheostoma are sister taxa, therefore some ichthyologists retain the genus Etheostoma for these darters while others recognize Nothonotus as a distinct genus.
Distribution of the Caney Fork Darter, Nothonotus starnesi, and other closely-related species in the Cumberland River drainage in Kentucky and Tennessee From figure 2 in Keck and Near 2013.
Citation for species description:
Keck, B.P., and T.J. Near. 2013. A new species of Nothonotus darter (Teleostei: Percidae) from the Caney Fork in Tennessee, USA. Bulletin of the Peabody Museum of Natural History 54:3-21.
 
Other citations:
Etnier, D.A., and W.C. Starnes. 1993. The Fishes of Tennessee. The University of Tennessee Press, Knoxville.
 
Near, T.J., C.M. Bossu, G.S. Bradburd, R.L. Carlson, R.C. Harrington, P.R. Hollingsworth Jr., B.P. Keck, and D.A. Etnier. 2011. Phylogeny and temporal diversification of darters (Percidae: Etheostomatinae). Systematic Biology 60:565-595.
 
Near, T.J., and B.P. Keck. 2013. Free from mitochondrial DNA: nuclear genes and the inference of species trees among closely related darter lineages (Teleostei: Percidae: Etheostomatinae). Molecular Phylogenetics and Evolution 66:868-876.
 
Near, T.J., and B.P. Keck. 2005. Dispersal, vicariance, and timing of diversification in Nothonotus darters. Molecular Ecology 14: 3485-3496.

4 comments:

Tom Near said...

This is a very nice write up of our paper. The only thing I will add is that a recent published phylogenetic analysis of 13 nuclear genes also supports the distinctiveness of Nothonotus, relative to Etheostoma.

Near, T. J. and B. P. Keck 2013. Free from mitochondrial DNA: Nuclear genes and the inference of species trees among closely related darter lineages (Teleostei: Percidae: Etheostomatinae). Molecular Phylogenetics and Evolution 66: 868-876.

Bernie Kuhajda said...

Thanks for the latest paper, I have updated the blog. Even with the 13 nuclear genes Nothonotus is within a monophyletic clade with and sister to Etheostoma, and increased taxon sampling within Etheostoma may produce other clades outside of the subgenus Etheostoma that are also distinct, therefore some ichthyologist are being conservative with their taxonomy until relationships are further resolved.

Tom Near said...
This comment has been removed by the author.
Tom Near said...

I understand this perspective. Nothonotus is sister to Etheostoma, so keep it in Etheostoma. This is a perfectly valid interpretation.

Our approach views having a singular name for a species rich lineage, like Etheostoma (s.l.), as not conveying the information that we now know from phylogeny. Also, the inclusive nature of Etheostoma is a consequence of the taxonomic history, where at a critical time there was not enough information to delineate all of the major lineages (genera) of darters.

I would suggest that it is not likely future phylogenetic analyses will resolve lineages of Etheostoma as more closely related to Nothonotus than they are to other Etheostoma. Given this premise, we are motivated by the fact that distinguishing Nothonotus makes Etheostoma less inclusive. We think this makes the name more informative, as now we know that all the species we call Etheostoma are more closely related to each other, relative to Nothonotus. If we keep Nothonotus as a subgenus in Etheostoma, you no longer have that information tied to the name. In other words, "Etheostoma" does not tell you that Nothonotus is the sister lineage to all other Etheostoma.

If you look at the taxonomic history of darters, Etheostoma was retained as a big inclusive genus because Bailey could only find diagnostic characters for Percina and Ammocrypta (including Crystallaria). In other words, Etheostoma was the group for any species that was not classified into either Percina or Ammocrypta (& Crystallaria). Bailey had no character that diagnosed Etheostoma. It was a taxonomic garbage can.

The argument that Nothonotus is sister to Etheostoma, so keep it in Etheostoma can be applied to Ammocrypta and Crystallaria. These two lineages clearly share common ancestry, so what is to be gained by recognizing Crystallaria and Ammocrpta as genera? The answer is the same for the Nothonotus-Etheostoma question. By having Ammocrypta and Crystallaria as distinct, you know that A. clara, A. meridiana, A. pellucida, A. beanii, A. vivax, etc., share common ancestry relative to C. asprella and C. cincotta.

As for other lineages of Etheostoma being elevated to genera, I am not sure that will happen. We know that Etheostoma is a clade relative to Ammocrypta, Crystallaria, Percina, and Nothonotus. However, relationships among the major lineages of Etheostoma are in flux, and very may well never be resolved. So I will offer a conservative opinion and recommend that no additional genera be peeled out of Etheostoma.

Thank you for this discussion! It is fun to talk about the science of darter phylogeny and what it means for classification.