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
Listening in: Acoustic monitoring devices detect illegal hunting and logging
14.12.2017 | Gesellschaft für Ökologie e.V.
How fires are changing the tundra’s face
12.12.2017 | Gesellschaft für Ökologie e.V.
DNA molecules that follow specific instructions could offer more precise molecular control of synthetic chemical systems, a discovery that opens the door for engineers to create molecular machines with new and complex behaviors.
Researchers have created chemical amplifiers and a chemical oscillator using a systematic method that has the potential to embed sophisticated circuit...
MPQ scientists achieve long storage times for photonic quantum bits which break the lower bound for direct teleportation in a global quantum network.
Concerning the development of quantum memories for the realization of global quantum networks, scientists of the Quantum Dynamics Division led by Professor...
Researchers have developed a water cloaking concept based on electromagnetic forces that could eliminate an object's wake, greatly reducing its drag while...
Tiny pores at a cell's entryway act as miniature bouncers, letting in some electrically charged atoms--ions--but blocking others. Operating as exquisitely sensitive filters, these "ion channels" play a critical role in biological functions such as muscle contraction and the firing of brain cells.
To rapidly transport the right ions through the cell membrane, the tiny channels rely on a complex interplay between the ions and surrounding molecules,...
The miniaturization of the current technology of storage media is hindered by fundamental limits of quantum mechanics. A new approach consists in using so-called spin-crossover molecules as the smallest possible storage unit. Similar to normal hard drives, these special molecules can save information via their magnetic state. A research team from Kiel University has now managed to successfully place a new class of spin-crossover molecules onto a surface and to improve the molecule’s storage capacity. The storage density of conventional hard drives could therefore theoretically be increased by more than one hundred fold. The study has been published in the scientific journal Nano Letters.
Over the past few years, the building blocks of storage media have gotten ever smaller. But further miniaturization of the current technology is hindered by...
11.12.2017 | Event News
08.12.2017 | Event News
07.12.2017 | Event News
15.12.2017 | Power and Electrical Engineering
15.12.2017 | Materials Sciences
15.12.2017 | Life Sciences