What do horses and cockroaches share?

Ectobius_pallidus. Photo: Didier Descouens, Museum of Toulouse/Wikipedia
Ectobius_pallidus. © Didier Descouens, Museum of Toulouse/Wikipedia

What does the humble Ectobius cockroach, the most common cockroach in Europe, have in common with horses?

It transpires the two share a somewhat similar history, according to researchers, having very possibly evolved in North America, become extinct there, only to be re-introduced thanks to mankind.

The Ectobius cockroach is a major textbook example of an invasive organism, inhabiting a large region from northernmost Europe to southernmost Africa.

It has a long fossil history in Europe, occurring in Baltic amber that is about 44 million years old. Its lineage was believed to have been exclusively from the Old World.

However, a new discovery has uprooted that view. It now appears that Ectobius may have originated in the New World.

Four ancient Ectobius species were recently discovered in the 49-million-year-old Green River Formation near Rifle, Colorado, in deposits that are about 5 million years older than the Baltic amber. However, these cockroaches soon became extinct in North America.

The cause for the extinction of Ectobius in North America in the dim past is unknown, but it evidently survived in the Old World, and western Europe in particular, as did horses.

“About 65 years ago, several entomologists in the northeastern United States noted that four species of Ectobius were present in North America,” one of the study’s authors, Dr Conrad Labandeira, said.

“It was always assumed that these four newcomers were the first Ectobius species to have ever lived in North America. But the discovery in Colorado proves that their relatives were here nearly 50 million years ago.”

The researchers, whose findings have been published by the Entomological Society of America, noted that in many ways the history of Ectobius mirrored that of the biogeographic history of the horse.

Horses occurred in the New World and became extinct during the late Pleistocene ecological crisis. Horses, attached to human habitation, were subsequently introduced to North America by early Spanish explorers about 11,000 years after their demise.

The newly discovered fossil species of Ectobius, specifically Ectobius kohlsi, are described in the January 2014 issue of Annals of the Entomological Society of America in an article called “Native Ectobius (Blattaria: Ectobiidae) From the Early Eocene Green River Formation of Colorado and Its Reintroduction to North America 49 Million Years Later.”

This particular species is named after David Kohls, who lives near Rifle, Colorado, and has been an indefatigable collector of fossil insects and plants from the nearby Green River Formation.

His collection of about 150,000 insects from 31,000 slabs of shale now constitutes the Kohls Green River Fossil Insect Collection, housed in the Smithsonian’s Department of Paleobiology.

The Entomological Society of America is the largest organization in the world serving the professional and scientific needs of entomologists and people in related disciplines.

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