Many darters are limited in geographical distribution--often endemic to a single drainage system--and the vermilion darter is no exception. The species is restricted to the headwaters of Turkey Creek, a tributary to the Locust Fork of the Black Warrior River, with a total range of only three stream miles. The species' isolation in Turkey Creek is what must have led to its divergence from other darters native to the Black Warrior. An eight- to twelve-foot-high waterfall occurs just below the vermilion darter's habitat, limiting its movement downstream while restricting other fish from entering the system. Mike Howell, a Samford University ichthyologist who first began to collect the species in 1964, points to the waterfall as a perfect mechanism for allopatric ("different country") speciation. In this type of speciation, a physical obstacle cuts off a small population from a larger one. Only inbreeding can then occur, and any differences with the main group become accentuated; after a number of generations, a "new" species is present, so different from the original that interbreeding becomes unlikely, if not impossible. The color patterns of vermilion darter males--slightly and subtlety different from Black Warrior types--offer an elegant example of such speciation in action.
Because the vermilion darter lives in suburban areas, subjected to silt and runoff pollution, many concerns exist as to its continued survival. The scientists who studied the species for the past thirty years document that its numbers have sharply dropped, prompting Boschung and Mayden to lament: "It is indeed unfortunate that we did not realize the uniqueness of the Turkey Creek darter twenty or thirty years ago. Measures could have been taken [at that time] to name and describe this rare species and therefore afford it the protection of an endangered species."
So the vermilion darter teaches us something about how speciation occurs and points out our obligation to protect all living creatures-both known and unknown. And we can learn these things right here at home.