Genetic swamping and possible species collapse: tracking introgression between the native Candy Darter and introduced Variegate Darter

  • Isaac Gibson
  • Amy B. WelshEmail author
  • Stuart A. Welsh
  • Daniel A. Cincotta
Research Article


Candy Darters (Etheostoma osburni) and Variegate Darters (E. variatum) are both native to West Virginia and Virginia. The geographic ranges of these two species were historically separated by Kanawha Falls, a natural barrier to fish dispersal located at Glen Ferris, WV. In the early 1980s, Variegate Darters or putative hybrids (E. osburni × E. variatum) were first collected at locations upstream of Kanawha Falls, and have since undergone range expansion. Hybridization with the Variegate Darter was one of the threats that led to the Candy Darter being listed as Endangered under the U.S. Endangered Species Act in 2018. Genetic and morphologic data were examined for individuals from the New, Gauley, and Greenbrier river drainages. Individuals were genotyped using a suite of 5 diagnostic microsatellite loci to investigate potential hybridization. Widespread hybridization was found throughout populations of Candy Darters, with the geographic range of hybridization expanding from 2004 to 2014. A hybrid zone was observed, with the highest levels of Variegate Darter introgression representing the kernel within this zone and the locations of first-generation (F1) hybrids at the periphery. F1 hybrids were morphologically intermediate within and across characters for parental species. Introgressive hybridization threatens the genetic integrity of the Candy Darter, and may lead to population extirpation or extinction.


Hybridization Genetic swamping Introgression Etheostoma osburni variatum 



This manuscript is dedicated to the memory of Isaac Gibson. The legacy of Isaac’s dedication and tireless commitment to the conservation of this special species will endure. The late Tim King deserves special recognition for his participation and guidance in the early stages of this research as well as his contributions to the field of conservation genetics; John Switzer for the collection of preliminary data; Angie Burns, Lara Hedrick, Jim Hedrick, Heather Hildebrand, Tim Hodge, Dustin Kimble, David Okernick, Nathaniel Owens, Ken Sheehan, David Thorne, and David Wellman for assistance with specimen collection; and Barbara Douglas for review of the manuscript. Funding for this research was provided by West Virginia Division of Natural Resources, State Wildlife Grant, the National Institute of Food and Agriculture, U.S. Department of Agriculture, Hatch Project WVA00690, and the West Virginia Agricultural and Forestry Experiment Station. This study was performed under the auspices of West Virginia University IACUC protocol 01-0510. Any use of trade, firm, or product names is for descriptive purposes only and does not imply endorsement by the U.S. Government.


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Copyright information

© Springer Nature B.V. 2018

Authors and Affiliations

  • Isaac Gibson
    • 1
  • Amy B. Welsh
    • 2
    Email author
  • Stuart A. Welsh
    • 3
  • Daniel A. Cincotta
    • 1
  1. 1.West Virginia Division of Natural ResourcesElkinsUSA
  2. 2.Division of Forestry and Natural ResourcesWest Virginia UniversityMorgantownUSA
  3. 3.U.S. Geological SurveyWest Virginia Cooperative Fish and Wildlife Research UnitMorgantownUSA

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