Nature Lab

Fisheries Science

Longnose Darter Study

DNA sequencing can reveal things that otherwise might go unnoticed — such as genetic variation within a species from one Ozark watershed to another. Recently, MDC and university researchers have been looking at genetic differences among populations of longnose darters across several states.

“The federal government was looking at listing the longnose darter as endangered,” explains MDC Geneticist and Biometrician Leah Berkman. “But the St. Francis population — the only existing population in Missouri — had not been studied. To know if it should be lumped in with the other longnose darters, we need to know how related they are.”

From 2017 to 2019, researchers collected tiny clippings from the tails of 35 longnose darters in the St. Francis River. DNA from these samples was compared to that of longnose darters from Oklahoma and Arkansas and to that of a similar species, the slenderhead darter.

“The process is pretty simple,” says Berkman. “The fish have many sequences in common, so these can be aligned to each other with a computer algorithm and then we look for places where they mismatch. Then those differences in DNA sequences are used to draw the family tree.”

This time the family tree provided “a big reveal,” Berkman says. “The longnose darters in the St. Francis River are different enough to be a separate species from those found in the Neosho and Arkansas rivers.”

What does this mean for conservation? The St. Francis River longnose darters could be declared a separate species and receive a new name. But regardless of the outcome, these darters contribute diversity to the larger group of closely related darters, and MDC will be safeguarding their unique genetics by protecting their habitat and preventing the introduction of other longnose darters into that region.

Longnose Darter Study at a Glance

DNA sequencing is helping scientists unravel the genetic relationships among darter species in the Ozarks, where areas isolated many years ago caused species to develop unique genetics and evolve. Recent analyses show that the longnose darters in Missouri’s St. Francis River are very genetically different from other longnose darters.

Cooperating Universities

• University of Missouri
• Tennessee Tech University
• Yale University

Longnose darters and slenderhead darters are part of a large group of closely related species, known as a species complex.

Learn more at short.mdc.mo.gov/4cM.