ANN ARBOR, Mich.---Think "mass extinction" and you probably envision dinosaurs dropping dead in the long-ago past or exotic tropical creatures being wiped out when their rainforest habitats are decimated. But a major mass extinction took place right here in North America in the first half of the 20th century, when 47 species of mollusk disappeared after the watershed in which they lived was dammed.
Now, a population of one of those species---a freshwater limpet last seen more than 60 years ago and presumed extinct---has been found in a tributary of the heavily dammed Coosa River in Alabama's Mobile River Basin. Researchers from the University of Michigan, the Alabama Aquatic Biodiversity Center and the Kentucky State Nature Preserves Commission reported the rediscovery May 31 in the online, open-access journal PLoS One.
The story of Rhodacmea filosa's disappearance and reappearance is both a conservation success story and a cautionary tale for other parts of the world where rivers are being dammed, said Diarmaid Foighil, professor of ecology and evolutionary and a curator at the U-M Museum of Zoology. It's also an example of how museum specimens collected generations ago can inform scientists of today.
Limpets are snails with shells shaped like caps rather than coils. They make their homes in the riffles and shoals of fast-flowing rivers and streams, where they graze on microscopic algae. When rivers are dammed, shoals and riffles are replaced with reservoirs, and the swiftly-moving water the limpets require is stilled.
The Mobile River Basin, a "global hotspot of temperate freshwater biodiversity," was extensively industrialized throughout the 20th century, and 36 major dams and locks were built. At the time, few thought much about preserving biodiversity. The prevailing attitude was, "What's not to like about getting electricity from a natural source---especially in impoverished, rural areas---and us
|Contact: Nancy Ross-Flanigan|
University of Michigan