Beginning with the pygmy sunfish, Quattro and colleagues examined the genetic makeup of fish species within the ancient freshwater drainage systems. They found the banded pygmy sunfish in all the South Carolina rivers in fact, this widespread species is found in nearly all the river systems of the U.S. southeastern and Gulf coasts, starting from the plains of North Carolina, around Florida, and all the way to and up the Mississippi River.
But two species are much rarer. The bluebarred pygmy sunfish is found only in the Savannah and Edisto systems. The Carolina pygmy sunfish is found only in the Santee and Pee Dee systems. Both species coexist with the common banded pygmy sunfish in these river systems, but are found nowhere else in the world.
From an evolutionary standpoint, it's a noteworthy finding. These rare species are related to the widespread species, yet the details of the inter-relationships such as which predates the others and is thus an ancestral species still defy ready description. The fact that a rare and a common species are located together in an ancient river system is important information in the ongoing struggle to clearly define evolutionary history. In the past, scientists drew taxonomic charts almost solely on the basis of physical structure (morphology) and available fossils. The genetic data revolution of recent decades is helping redefine biology in a much more precise manner, but the process is still in the early going.
From the river to the sea
Quattro has been doing his part by slowly moving down the river systems to the ocean, collecting genetic data the whole way down. In the freshwater rivers, he has examined pygmy sunfishes, other sunfishes and basses. Closer to the sea, he has looked at short-nosed sturgeon, which spend most of their time in the estuary (where the river meets the ocean), but do venture up the river to spawn. And further downriver still, he has looke
|Contact: Steven Powell|
University of South Carolina