Unknown to many, West Virginia is home to its own ecosystem of rare species. Like many places in the world, human impact has had negative effects on those species, endangering their very existence.
Conservation geneticist and West Virginia University researcher Amy Welsh learned about such a species in Fayette County through her work at Kanawha Falls. The falls were, for a long time, a barrier between two bait fish: the candy and variegate darters.
A small, brightly colored fish, the candy darter is endemic to a very narrow range
above the falls in West Virginia and some of Virginia. Until recently, it never
interacted with the variegate darter which lived below the falls.
“We think that due to people fishing with the variegate darter as live bait, it was introduced above Kanawha Falls into the candy darter’s range,” Welsh said. "Once that happened, the variegate darter started mating with and hybridizing with the candy darter.”
The hybrids have actually fared well - too well in fact. It has led to genetic swamping where they’ve essentially taken over. Now, the candy darter is endangered.
Hybridization was first suspected in 1991 when the National Parks Service collected five fish that didn’t quite look like either species; however, Welsh’s candy darter research didn’t begin until 2014.
Over the last six years, she used genetic analysis to truly discover if the variegate darter was breeding with the candy darter.
“That’s difficult to tell morphologically. You really have to use genetics to see if hybridization is occurring and to see if hybridization is successful. We found five diagnostic genetic markers that clearly differentiate the candy and the variegate.”
With an understanding of what the candy darter population looked like before the variegate darter was introduced, Welsh was able to determine only eight of 35 populations remained, a substantial loss of the candy darter populations due to hybridization.
Experts, including Welsh, believed the best and possibly only way to save the candy darter was to have it listed under the Endangered Species Act.
In 2015, The Center for Biological Diversity sued the Fish and Wildlife Service to evaluate the candy darter and it was proposed the species be listed as “threatened.”
“When the Fish and Wildlife Service initially came up with the ruling, they were treating each population as candy darter populations whether they were hybrids or pure since the Endangered Species Act does not have a formal policy on how to treat hybrids,” she said.
However, after Welsh and other scientists argued a totally hybridized population shouldn’t be counted as an intact candy darter population, the Fish and Wildlife Service changed the final listing to “endangered.”
The 2018 decision required the federal agency to designate critical habitat and come up with a recovery plan.
Although the federal plan is not yet finalized, several state regulations have been put in place including making it illegal to possess a darter and designating fishing waters where live bait is not allowed.
According to Welsh, the regulations will help reduce the spread of the hybrid populations, but they move a lot more than previously suspected.
“They’re going to continue to spread, and there’s nothing we can do to prevent that,” she said. “It’s something to take into account when we think about dam removal, for example, because that can also help further the spread of variegate darters.”
Since the candy darter is only found in West Virginia and Virginia, scientists in the two states are considering how their respective candy darter populations can help the other.
“We’ve just recently completed a genetic analysis looking at West Virginia and Virginia together and ways that we could probably help,” Welsh said. In Virginia the threats are a little bit different. Variegate darters have not been introduced in the candy darter’s range. Instead, there are these really small, isolated populations of candy darters. We could help by introducing more candy darters to increase the genetic diversity in their populations.”
Virginia, in turn, may be able to help the West Virginia candy darter by providing suitable habitat free of variegate darters.
As plans are being made to help save the candy darter, the effects of the majority loss - and potential extinction - are uncertain.
“We don’t think we have a solid answer on what the ecological consequences are going to be. And, honestly, there may not be any ecological consequences because the variegate darter may just fill the niche of the candy darter,” Welsh said. “I think there are probably going to be few ecological consequences of its extinction. So it becomes more about the intrinsic value of this species.”