Mismatched feet may be a sign of population stress.
© Lens et al.
Asymmetric bodies fuel arguments over ecological risk.
Birds with one foot bigger than the other are showing signs of stress, say Belgian ecologists. The study backs the controversial idea that measuring body asymmetries could signal that a species is at risk.
Researchers at the University of Antwerp measured the feet of taita thrushes from three remaining pockets of their native forest in Kenya. Those from the most disturbed area showed eight times more difference between the size of their left and right feet than the least disturbed - a sign of future decline, they say1.
In general, the studies that find a correlation are the ones that get published; those that don’t, rarely make it into print. This issue has given ’fluctuating asymmetry’ a chequered history, with as many sceptics as believers.
Finding the mechanism underlying the disparity will be key to settling the debate. "We’re not at the stage that we understand enough about it and why in some cases it works and others it doesn’t," says conservation biologist Andrew Balmford at the University of Cambridge, UK.
Lens argues that the foot measure in thrushes reveals an indirect link between asymmetry and survival. It is an indicator of a male’s overall quality, he suggests - important to females, who choose the most symmetrical mates. Thus increased asymmetry may imply that a male is less fit. "People wrongly assume that because the differences are so small, the impact or biological relevance is also small," says Lens.
Many who have studied fluctuating asymmetry will not be convinced of its general utility until it can be proven under controlled situations. "When people have examined fluctuating asymmetry and stress in experimental lab conditions, the basic incontrovertible finding is that there is no consistent linkage," argues Andrew Pomiankowski, a geneticist at University College London.
Lens and his colleagues acknowledge that previous work has suffered from confounding measurement errors. But they claim to have developed new statistical methods that accurately separate variation caused by asymmetry from measurement error.
Pomiankowski agrees that for this particular trait in this species, Lens and his group may have found a real difference, but that it can’t be assumed to work elsewhere. It will have to be determined on a case by case study, says Pomiankowski - there is no universal trait that will indicate an individual’s fitness.
Asymmetry measures might be most useful if they could pick up insidious, hard-to-detect threats, suggests Balmford, such as the spread of disease, rather than stresses resulting from habitat decline. There are about 1,350 thrushes in the region studied by Lens, but the most degraded area has a declining population and the fewest individuals.
VIRGINIA GEWIN | © Nature News Service
Despite government claims, orangutan populations have not increased. Call for better monitoring
06.11.2018 | Deutsches Zentrum für integrative Biodiversitätsforschung (iDiv) Halle-Jena-Leipzig
Increasing frequency of ocean storms could alter kelp forest ecosystems
30.10.2018 | University of Virginia
Researchers at the University of New Hampshire have captured a difficult-to-view singular event involving "magnetic reconnection"--the process by which sparse particles and energy around Earth collide producing a quick but mighty explosion--in the Earth's magnetotail, the magnetic environment that trails behind the planet.
Magnetic reconnection has remained a bit of a mystery to scientists. They know it exists and have documented the effects that the energy explosions can...
Biochips have been developed at TU Wien (Vienna), on which tissue can be produced and examined. This allows supplying the tissue with different substances in a very controlled way.
Cultivating human cells in the Petri dish is not a big challenge today. Producing artificial tissue, however, permeated by fine blood vessels, is a much more...
Faster and secure data communication: This is the goal of a new joint project involving physicists from the University of Würzburg. The German Federal Ministry of Education and Research funds the project with 14.8 million euro.
In our digital world data security and secure communication are becoming more and more important. Quantum communication is a promising approach to achieve...
On Saturday, 10 November 2018, the research icebreaker Polarstern will leave its homeport of Bremerhaven, bound for Cape Town, South Africa.
When choosing materials to make something, trade-offs need to be made between a host of properties, such as thickness, stiffness and weight. Depending on the application in question, finding just the right balance is the difference between success and failure
Now, a team of Penn Engineers has demonstrated a new material they call "nanocardboard," an ultrathin equivalent of corrugated paper cardboard. A square...
09.11.2018 | Event News
06.11.2018 | Event News
23.10.2018 | Event News
16.11.2018 | Health and Medicine
16.11.2018 | Life Sciences
16.11.2018 | Life Sciences