Ben Keck and I just published the attached paper that demonstrates extensive mtDNA transfer among Nothonotus species. The mechanism for this transfer of mtDNA genomes is hybridization. The Redline Darter is one of the main players in this history of hybridization among species of Nothonotus.

I knew it! So much for being playfully ridiculled all the time about the redline/bluebreast hybrids I said I was collecting from the Holston and Hiwassee.

Tom, what do you think is going on with the chlorobranchius mtDNA showing up in rufilineatus from streams (Sequatchie, Emory/Obey) one would never have thought of as having chlorobranchius even hundreds of years ago? Or am I misinterpreting the table? Is that rufilineatus acting as a conduit for chlorobranchius mtDNA?

Todd and I have spoke a few times about the rufilineatus in the Caney, Roaring streams and some potential ecological explinations of what you and Ben see (I believe I even mentioned to Ben before when talking about potential sanguifluus records). They almost appear to be exhibiting invasive traits and along with the disturbed habitat may have displaced other Nothonotus, especially the more endemic species, both physically and genetically. You could probably also apply that hypothesis to the Stones where microlepedius has also seen significant declines.

Ben and I are hypothesizing that N. rufilineatus has expanded the geographic distribution of N. chlorobranchius mtDNA. We are not sure if this represents what is called a selective sweep, where on mtDNA genome has a selective advantage and is rapidly expanded in the populations, or if there is a history of dispersal of redlines from the upper Tennessee to tributaries downstream that would carry the introgressed chlorobranchius mtDNA.

Were the hybrids you observed in the Holston and Hiwassee F1s between rufilineatus and camurus? There are a number of these hybrids reported in Keck and Near (2009: Copeia). Not sure where they are from, but Ben would have that data.

When you talk about redlines in the Caney, are you referring to Sink Creek? The species is not in the Caney above the falls. This is dramatically illustrated in the range map that is a part of Figure 1 in Ben's Evolution paper.

Yes, I would call have called them F1 rufilineatus camarus.

I should clarify, I meant the lack of Caney watershed rufilineatus in comparison to their distribution in the nearby smaller watersheds of the Middle (?) Cumberland, such as Blackburn Fork, Roaring River, Spring Creek. Still trying to mentally digest this paper.

The two large gaps in Cumberland distribution of rufilineatus (Caney and Big South Fork) still have nice populations of sanguifluus....just sayin. Has the term niche bully been coined yet?

There are F1 specimens of N. camurus X N. rufilineatus from the Holston, Nolichucky, and Clinch; Charlie Saylor says the Emory used to be full of them as well (probably is again). I don't think the camurus mtDNA is going to replace the chlorobranchius mtDNA in the upper TN, and do think these are probably just F1 individuals or limited back crosses.

Figuring out the mechanisms responsible for the extensive geographic replacement is one of my big goals that will take a bit of experimentation.

I've thought about the apparent allopatry of N. rufilineatus/N. sanguifluus, but have to wonder if the rufs didn't replace the sanguifluus after the sanguifluus were extirpated due to dams or pollution. The last records of sanguifluus from those rivers are fairly soon after the major dams in that area went in, and those areas had some decent pollution from mining and smelting to boot. The model explaining replacement probably has some additive factors in there.

I'd be interested in any camurus X rufilineatus from the Hiwassee... or any N. camurus for that matter, given there are only a few known N. camurus specimens from there.