A seleção natural é muito preguiçosa: espécie viva de besouro aquático encontrada em sedimentos de 20 milhões de anos!

sábado, outubro 08, 2011

Living Species of Aquatic Beetle Found in 20-Million-Year-Old Sediments

ScienceDaily (Oct. 6, 2011) — A study of an Early Miocene fossil from southern Siberia performed by an international team of researchers, from the National Museum in Prague, Voronezh State University and the Museum of Natural History in London, led to the surprising find that the fossil belongs to a species of aquatic beetles which is still alive today and widely distributed in Eurasia.

General view of the modern Helophorus sibiricus and its newly discovered Early Miocene fossil counterpart. The close-ups show the species-specific granulation of the pronotum in both the recent specimen (top) and the fossil (bottom), one of the characteristics that allowed a reliable identification of the 20-million-year-old specimen. (Credit: Martin Fikáček)

The study was published in the open-access journal ZooKeys.

The fossil beetle discovered in the 16-23 million years old sediments of the Irtysh River in southern Siberia belongs to the modern speciesHelophorus sibiricus, a member of the water scavenger beetles (Hydrophiloidea), which is at present widely distributed in Eurasia and reaches even North America. The species was originally described in 1860 by the Russian entomologist Victor Motschulsky based on specimens collected at Lake Baikal. It is aquatic and inhabits various kinds of standing waters, predominantly the grassy temporary pools. Larvae are unknown so far, but are supposed to be terrestrial and predaceous, preying on various invertebrates, as in most other species of the genus.

The Siberian fossil provides new data for the long-lasting debate among scientists about the average duration of an insect species. It was originally estimated to be ca. 2-3 million years based on the available fossil record, but slowly accumulating data begin to show that such an estimate is an oversimplification of the problem. Recently, evolutionary trees dated using molecular clocks suggested that some insect species are rather young, originating during the Ice Ages, but others may have been able to survive the last 10-20 million years until today. The long-living species had to survive the massive changes of the Earth's climate during the last millions of years -- how they managed to do so is another question for scientists to address.

Read more here/Leia mais aqui: Science Daily

ZooKeys 130 (2011) : Special issue: 239-254

Advances in the Systematics of Fossil and Modern Insects: Honouring Alexandr Rasnitsyn 

A long-living species of the hydrophiloid beetles:Helophorus sibiricus from the early Miocene deposits of Kartashevo (Siberia, Russia)
Martin Fikácek, Alexander Prokin, Robert Angus

doi: 10.3897/zookeys.130.1378
Published: 24.09.2011 
The recent hydrophiloid species Helophorus (Gephelophorus) sibiricus(Motschulsky, 1860) is recorded from the early Miocene deposits of Kartashevo assigned to the Ombinsk Formation. A detailed comparison with recent specimens allowed a confident identification of the fossil specimen, which is therefore the oldest record of a recent species for the Hydrophiloidea. The paleodistribution as well as recent distribution of the species is summarized, and the relevance of the fossil is discussed. In addition, the complex geological settings of the Kartashevo area are briefly summarized.