Mitochondrial and nuclear introgression among closely related taxa can greatly complicate the process of determining their phylogenetic relationships. In the Central Highlands of North America, many fish taxa have undergone introgression; in this study, we demonstrate the existence of an unusual introgression event in the Etheostoma zonale species group. We used one mitochondrial and seven nuclear loci to determine the relationships of the taxa within the E. zonale group, and their degree of differentiation. We found evidence of multiple divergent populations within each species; much of the divergence within species has taken place during the Pleistocene. We also found evidence of a previously unknown cryptic species in the Upper Tennessee River which diverged from the remainder of the group during the Pliocene, and has undergone mitochondrial and nuclear introgression with E. zonale, in an apparent process of speciation reversal. We examined the effects that using varying types of recombination tests to eliminate the signal of recombination from nuclear loci would have on the phylogenetic placement of this introgressed lineage in our species tree analyses.
Bibliographical noteFunding Information:
This study represents a chapter in D.H.’s dissertation that was submitted in partial fulfillment of the PhD degree, awarded by the Department of Ecology, Evolution and Behavior at the University of Minnesota. We thank S. Jansa, S.M. Lanyon, G. Weiblen, K. Kozak and F.K. Barker for valuable discussions; B. Nagle, J.J.D. Egge, M. Ghedotti, M.V. Hirt, B. Young, and P. Hundt for field assistance; and B. Befort for assistance in the laboratory. J.J.D. Egge at Pacific Lutheran University, B.R. Kuhajda at the University of Alabama, R.L. Mayden and R.M. Wood at St. Louis University, T.J. Near at Yale University, and M. Roberts at the Mississippi Museum of Natural Science provided specimens; all remaining fish were collected under appropriate state permits issued to A.M.S. or D.H. We thank the editor and two anonymous reviewers for helpful comments which aided in the revision of this paper. Funding was provided through Dayton-Wilkie Fellowships from the Bell Museum of Natural History and an award from the National Science Foundation (DEB-0909770) to D.H.
- Species trees