. Earth Science News .

Evolution in an island, the secret for a longer life
by Staff Writers
Barcelona, Spain (SPX) Apr 27, 2012

Myotragus balearicus lower jaws. The upper part shows the jaw of a young adult specimen with extremely high teeth. The upper right image corresponds to the x-ray of the jaw. The jaw below belongs to a very old specimen, which shows fully worn teeth, i.e., without enamel. Credit: Institut Catala de Paleontologia Miquel Crusafont.

ICP researchers published in the 'Proceedings of the Royal Society B' one of the first fossil-based evidences supporting the evolutionary theory of ageing, which predicts that species evolving in low mortality and resource-limited ecosystems tend to be more long-lived.

The study shows that the tooth height of endemic insular mammals is an indicator of longevity, and questions the use of this morphological characteristic as an exclusive indicator to infer the diet of fossil species, and to interpret the climate in which they lived.

Island systems often function as natural laboratories to test evolutionary hypotheses, since they are less complex than continental systems. Increased longevity of insular endemic species is an adaptation that the evolutionary theory of ageing predicts, as part of an evolutionary strategy that pushes the islands' endemics to a slower life cycle, due to the absence of predators and the limited resources.

In this context, Xavier Jordana and the researchers who sign the work published in the online edition of the Proceedings of the Royal Society B wonder if the increased height of the teeth of herbivores endemic to islands may be an evolutionary response to this longevity. This would call into question the consensus that so far explained this morphological characteristic from differences on diet and climate.

The paper "Evidence of correlated evolution of hypsodonty and exceptional longevity in endemic insular mammals" concludes that indeed Myotragus balearicus, the fossil species chosen for this study, needed higher teeth to get to live as long as it did. Hypsodonty, as experts call having a high dental crown, can be an indicator of long-lived species.

As explained by the ICP researcher Xavier Jordana, lecturer at the Universitat Autonoma de Barcelona in the masters in Human Biologya and in Paleontology and main author of this work, "the study focuses on a fossil species, but our results have implications for herbivorous mammals in general, extinct and extant, and especially in insular endemic species.

The latter share some common characteristics, known as the island syndrome, which are different from their mainland relatives, as they evolve in special ecological conditions, such as the lack of predators, high population density and limited resources."

The research now published analyzes the diet, longevity and mortality patterns of M. balearicus, a fossil bovid endemic to the Balearic Islands. The paper concludes that, despite being extremely hypsodont, M. balearicus was mostly a browser, that fed on leaves and shoots of trees and shrubs, and probably also tubers and roots, which involve excessive abrasion of the teeth because they have to dig into the ground to reach them.

They did not have such an abrasive diet as grazers, which feed mainly of grasses and, therefore, exhibit higher teeth. The feeding habits, however, are not sufficient to explain the hypsodonty of Myotragus.

By analyzing M. balearicus longevity from annual growth lines of the teeth cementum, the researchers obtained a calculation of about 27 years, almost doubling that expected for a bovid of such body mass. In addition, the study of mortality patterns in two populations of M. balearicus, one from Cova Estreta and another from Cova des Moro in Mallorca, show juvenile and adult survival rates higher than in extant continental bovids.

This means that a large proportion of the population reached greater ages and, therefore, M. balearicus was a species with a slow senescence rate, ie. with late ageing.

These results are consistent with the evolutionary theory of ageing that predicts the delay of senescence in populations with low extrinsic mortality. In an environment where few external elements can cause death of individuals, such as the lack of predators on an island, the species adapts by changing its ageing rate and lifespan. For herbivores one way to do that is to select those individuals in the population with higher teeth, for which senescence starts later.

The fossil genus Myotragus has been an ideal model for evolution studies in islands and M. balearicus is the terminal species, which became extinct about 3,000 years ago. Myotragus survived completely isolated in Mallorca and Menorca for more than 5 million years, from the Pliocene to the Holocene.

During its evolution Myotragus underwent significant changes, particularly affecting the locomotor system and its body size, as well as its nervous system and feeding apparatus. Dwarfism, reduced brain size and changes in dentition are the most distinctive evolutionary traits. Many of these morphological features are shared by all the island fauna, as is the case with the increased crown height of the molar teeth.

The study is based on fossil remains of M. balearicus, recovered at different sites of Mallorca, especially Cova Estreta (Pollenca), Cova des Moro (Manacor) and Cova Moleta (Soller). Currently, these fossils are deposited in the collections of the Museum of the Miquel Crusafont Catalan Institute for Paleaontology in Sabadell, and of the Mediterranean Institute for Advanced Studies and the Balearic Museum of Natural Sciences in Mallorca.

Related Links
Universitat Autonoma de Barcelona
Darwin Today At TerraDaily.com

Get Our Free Newsletters Via Email
Buy Advertising Editorial Enquiries


. Comment on this article via your Facebook, Yahoo, AOL, Hotmail login.

Share this article via these popular social media networks
del.icio.usdel.icio.us DiggDigg RedditReddit GoogleGoogle

Nearly Seven million birds die each year at communication towers
Washington DC (SPX) Apr 27, 2012
More than 6 million birds die every year as they migrate from the United States and Canada to Central and South America, according to a new study published in the open access journal PLoS ONE. The birds are killed by the 84,000 communication towers that dot North America and can rise nearly 2,000 feet into the sky. "This is a tragedy that does not have to be," said lead author Travis Longc ... read more

S. Korea nuclear safety agency probes two plants

Construction of Chernobyl shelter starts on anniversary

Sean Penn urges more aid for Haiti

Hong Kong holds nuclear accident drill

I like to break things

Beyond stain-resistant: New fabric coating actively shrugs off gunk

Scientists Predict Paradoxical Laser Effect

Japan, Kazakhstan to jointly develop rare earths: report

Eight species of wild fish have been detected in aquaculture feed

Xayaburi Dam construction to continue?

Research is ensuring stormwater systems are designed for the future

Planned dams in Amazon may have largely negative ecosystem impact

Northern Canada feels the heat - Climate change impact on permafrost zones

Study Finds Surprising Arctic Methane Emission Source

State of Himalayan glaciers less alarming than feared

Breaking the Ice on Icebergs

Drought-resistant Argentine soy raises hopes, concerns

Brazilian farming association to open office in China

Autumn advantage for invasive plants in eastern United States

Hong Kong suspends poultry imports from China province

Rapid tsunami warning by means of GPS

Russian volcano spews ash into atmosphere

GPS could speed up tsunami alert systems: researchers

NASA's New Satellite Movie of One Week's Ash Activity from Mexico's Popocatepetl Volcano

West African summit on Guinea-Bissau set for Thursday

Sierra Leone's gruesome 10-year civil war

Stench of death in Heglig, where Sudan says 1,200 died

Mali junta yet to return to barracks: groups

Rio Summit must address population growth: scientists

Scientists show how social interaction and teamwork lead to human intelligence

NIST mini-sensor measures magnetic activity in human brain

Meat eating led to earlier weaning, helped humans spread across globe

Memory Foam Mattress Review

Newsletters :: SpaceDaily Express :: SpaceWar Express :: TerraDaily Express :: Energy Daily
XML Feeds :: Space News :: Earth News :: War News :: Solar Energy News


The content herein, unless otherwise known to be public domain, are Copyright 1995-2012 - Space Media Network. AFP, UPI and IANS news wire stories are copyright Agence France-Presse, United Press International and Indo-Asia News Service. ESA Portal Reports are copyright European Space Agency. All NASA sourced material is public domain. Additional copyrights may apply in whole or part to other bona fide parties. Advertising does not imply endorsement,agreement or approval of any opinions, statements or information provided by Space Media Network on any Web page published or hosted by Space Media Network. Privacy Statement