Tag: Science Magazine

“Gambling” wolves take more risks than dogs

Selected coverage: Science Magazine, Independent, Christian Science Monitor

Wolves pursue a high-risk, all-or-nothing strategy when gambling for food, while dogs are more cautious, shows a new study. This difference is likely innate and adaptive, reflecting the hunter versus scavenger lifestyle of wolves and dogs.

Would you rather get 100 euros for certain, or have a fifty-fifty chance of receiving either 200 euros or nothing? Most choose the first, as humans tend to be “risk-averse”, preferring a guaranteed pay-off over the possibility of a greater reward. It is thought that this human preference for “playing it safe” has evolved through natural selection: when you live precariously like our remote ancestors, losing all your food reserves might be catastrophic, while adding to them might makes less difference to your chances of survival.

Here, in one of the first studies on risk preferences in non-primates, scientists show through a series of controlled experiments that wolves are consistently more prone to take risks when gambling for food than dogs. When faced with the choice between an insipid food pellet and a fifty-fifty chance of either tasty meat or an inedible stone, wolves nearly always prefer the risky option, whereas dogs are more cautious.

“We compared the propensity to take risks in a foraging context between wolves and dogs that had been raised under the same conditions,” says Sarah Marshall-Pescini, a postdoctoral fellow at the University of Vienna and the Wolf Science Centre, Ernstbrunn, Austria, the study’s first author. “We found that wolves prefer the risky option significantly more often than dogs. This difference, which seems to be innate, is consistent with the hypothesis that risk preference evolves as a function of ecology.”

The study was done at the Wolf Science Centre, Ernstbrunn, Austria, a research institute where scientists study cognitive and behavioral differences and similarities between wolves and dogs. Here, wolves and dogs live in packs, under near-natural conditions within large enclosures.

Marshall-Pescini let each of 7 wolves and 7 dogs choose 80 times between two upside-down bowls, placed side-by-side on a moveable table-top. The animals had been trained to indicate the bowl of their choice with their paw or muzzle, after which they would receive the item that was hidden beneath it.

The researchers had taught the wolves and dogs that beneath the first bowl, the “safe” option, was invariably an insipid dry food pellet, while beneath the second bowl, the “risky” option, was either an inedible item, a stone, in a random 50% of trials, and high-quality food, such as meat, sausage, or chicken, in the other 50%. The side for the “safe” and “risky” option changed between trials, but the animals were always shown which side corresponded to which option; whether they would get a stone or high-quality food if they chose the “risky” option was the only unknown. Rigorously designed control trials confirmed that the animals understood this rule, including the element of chance.

Wolves are much more prone to take risks than dogs, show the results. Wolves chose the risky option in 80% of trials, whereas dogs only did so in 58% of trials.

The researchers believe that dogs evolved a more cautious temperament after they underwent an evolutionary shift from their ancestral hunter lifestyle to their current scavenger lifestyle, which happened between 18,000 to 32,000 years ago when humans first domesticated dogs from wolves. Previous research has suggested that species that rely on patchily distributed, uncertain food sources are generally more risk-prone. For example, chimpanzees, which feed on fruit trees and hunt for monkeys, have been shown to be more risk-prone than bonobos, which rely more on terrestrial vegetation, a temporally and spatially reliable food source.

“Wild wolves hunt large ungulates – a risky strategy, not only because hunts often fail, but also because these prey animals can be dangerous – whereas free-ranging dogs, which make up 80% of the world’s dog population, feed mostly by scavenging on human refuse, a ubiquitous, unlimited resource. So dogs no longer need to take risks when searching for food, and this may have selected for a preference to play it safe.” concludes Marshall-Pescini.

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Freya and Etu, a dog and wolf from the Wolf Centre. Credit: RoooBert Bayer

 

 

 

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Etu and Ela, wolf pups at the Wolf Centre. Credit: RoooBert Bayer
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Geronimo chose the “risky” option in 78% of trials. Credit: RoooBert Bayer

Fifteen shades of photoreceptor in a butterfly’s eye

Selected coverage: ABC, Christian Science Monitor, Science Magazine, Süddeutsche Zeitung

When researchers studied the eyes of Common Bluebottles, a species of swallowtail butterfly from Australasia, they were in for a surprise. These butterflies have large eyes and use their blue-green iridescent wings for visual communication – evidence that their vision must be excellent. Even so, no-one expected to find that Common Bluebottles (Graphium sarpedon) have at least 15 different classes of “photoreceptors” — light-detecting cells comparable to the rods and cones in the human eye. Previously, no insect was known to have more than nine.

“We have studied color vision in many insects for many years, and we knew that the number of photoreceptors varies greatly from species to species. But this discovery of 15 classes in one eye was really stunning,” says Kentaro Arikawa, Professor of Biology at Sokendai (the Graduate University for Advanced Studies), Hayama, Japan and lead author of the study.

Have multiple classes of photoreceptors is indispensable for seeing color. Each class is stimulated by light of some wavelengths, and less or not at all by other wavelengths. By comparing information received from the different photoreceptor classes, the brain is able to distinguish colors.

Through physiological, anatomical and molecular experiments, Arikawa and colleagues were able to determine that Common Bluebottles have 15 photoreceptor classes, one stimulated by ultraviolet light, another by violet, three stimulated by slightly different blue lights, one by blue-green, four by green lights, and five by red lights.

Why do Common Bluebottles need so many classes of photoreceptor? After all, many other insects have only three classes of photoreceptor and yet have excellent color vision. Likewise, humans have only three classes of cones, enough to distinguish millions of colors.

Arikawa and his colleagues believe that Common Bluebottles use only four classes of photoreceptor for routine color vision, and use the other eleven to detect very specific stimuli in the environment, for example fast-moving objects against the sky or colorful objects hidden among vegetation. A similar system is found in another butterfly previously studied by the same research group, the Asian swallowtail Papilio xuthus, which has six photoreceptors.

“Butterflies may have a slightly lower visual acuity than ourselves, but in many respects they enjoy a clear advantage over us: they have a very large visual field, a superior ability to pursue fast-moving objects and can even distinguish ultraviolet and polarized light. Isn’t it fascinating to imagine how these butterflies see their world?” says Arikawa.

The results are published in the open-access journal Frontiers in Ecology and Evolution.

EurekAlert! PR: http://www.eurekalert.org/pub_releases/2016-03/f-fso030116.php

Study: http://journal.frontiersin.org/article/10.3389/fevo.2016.00018/full

Scientists date the origin of the cacao tree to 10 million years ago

Selected coverage: Science Magazine, The Times Scotland, Daily Mail, Tech Times, Live Science,

With Shauna Hay, Royal Botanic Garden Edinburgh, UK

New research shows that cacao trees evolved around 10 million years ago, earlier than previously believed. Considerable genetic variation might remain to be discovered among wild cacao populations, which could be crossbred with cultivated cacao for greater resistance to disease and climate change.

Chocolate, produced from seeds of the cacao tree Theobroma cacao, is one of the most popular flavors in the world, with sales around 100$ billion dollars per year. Yet, as worldwide demand increases, there are fears the industry will fail to cope with growing public hunger for the product. The main problem, common to many crops, is the lack of genetic variation in cultivated cacao, which makes it vulnerable to pests and blights. Lack of genetic variation also puts cacao trees at risk from climate change, jeopardizing the long-term sustainability of the industry.

Now, however, new research suggests the cacao tree is much older than previously realised — and may have close relations capable of sustaining our sweet-toothed appetites.

“Studies of the evolutionary history of economically important groups are vital to develop agricultural industries, and demonstrate the importance of conserving biodiversity to contribute towards sustainable development. Here we show for the first time that the source of chocolate, Theobroma cacao, is remarkably old for an Amazonian plant species,” says Dr James Richardson, a tropical botanist at the Royal Botanic Garden Edinburgh, UK, and lead author of the study.

Together with researchers from the University of Rosario and the University of the Andes in Colombia, the University of Miami, USA, and the United States Department of Agriculture (USDA), Richardson found that Theobroma cacao is one of the oldest species in the genus Theobroma, having evolved around 10 million years ago. At the time, the Andes were not yet fully elevated, which explains why cacao trees today occur on both sides of the Andes.

The species’ early evolutionary origin is good news: it suggests that cacao has had enough time to diversify genetically, with each wild population adapting to its local habitat. Wild populations of cacao across the Americas may therefore be treasure troves of genetic variation, which could be bred into cultivated strains to make the latter more resistant to disease and climate change, and perhaps even create new flavors of chocolate.

“After ten million years of evolution we should not be surprised to see a large amount of variation within the species, some of which might exhibit novel flavours or forms that are resistant to diseases. These varieties may contribute towards improving a developing chocolate industry,” says James Richardson.

The researchers already plan to return to South America to sample all species related to cacao and investigate the characteristics of their native populations.

“We hope to highlight the importance of conserving biodiversity so that it can be used to augment and safeguard the agricultural sector. By understanding the diversification processes of chocolate and its relatives we can contribute to the development of the industry and demonstrate that this truly is the Age of Chocolate,” says coauthor Dr Santiago Madriñán of the University of the Andes in Bogotá, Colombia.

The study is published in the open-access journal Frontiers in Ecology and Evolution.

EurekAlert! PR: http://www.eurekalert.org/pub_releases/2015-11/f-sdt110515.php

Study: http://journal.frontiersin.org/article/10.3389/fevo.2015.00120/full

New fossils push the origin of flowering plants back by 100 million years to the early Triassic

Selected coverage: Science Magazine, Der Spiegel, BBC, NBC, Discovery News, The Independent

Drilling cores from Switzerland have revealed the oldest known fossils of the direct ancestors of flowering plants. These beautifully preserved 240-million-year-old pollen grains are evidence that flowering plants evolved 100 million years earlier than previously thought, according to a new study in the open-access journal Frontiers in Plant Science.

Flowering plants evolved from extinct plants related to conifers, ginkgos, cycads, and seed ferns. The oldest known fossils from flowering plants are pollen grains. These are small, robust and numerous and therefore fossilize more easily than leaves and flowers.

An uninterrupted sequence of fossilized pollen from flowers begins in the Early Cretaceous, approximately 140 million years ago, and it is generally assumed that flowering plants first evolved around that time. But the present study documents flowering plant-like pollen that is 100 million years older, implying that flowering plants may have originated in the Early Triassic (between 252 to 247 million years ago) or even earlier.

Many studies have tried to estimate the age of flowering plants from molecular data, but so far no consensus has been reached. Depending on dataset and method, these estimates range from the Triassic to the Cretaceous. Molecular estimates typically need to be “anchored” in fossil evidence, but extremely old fossils were not available for flowering plants. That is why the present finding of flower-like pollen from the Triassic is significant, according to the team of researchers who made the discovery.

Peter Hochuli and Susanne Feist-Burkhardt from the University of Zürich studied two drilling cores from Weiach and Leuggern, northern Switzerland, and found pollen grains that resemble fossil pollen from the earliest known flowering plants. With Confocal Laser Scanning Microscopy, they obtained high-resolution images across three dimensions of six different types of pollen.

In a previous study from 2004, Hochuli and Feist-Burkhardt documented different, but clearly related flowering-plant-like pollen from the Middle Triassic in cores from the Barents Sea, south of Spitsbergen. The samples from the present study were found 3000 km south of the previous site. The authors believe that even highly cautious scientists will now be convinced that flowering plants evolved long before the Cretaceous.

What might these primitive flowering plants have looked like? In the Middle Triassic, both the Barents Sea and Switzerland lay in the subtropics, but the area of Switzerland was much drier than the region of the Barents Sea. This implies that these plants occurred across a broad ecological range. The pollen’s structure suggests that the plants were pollinated by insects: most likely beetles, as bees would not evolve for another 100 million years.

EurekAlert! PR: http://www.eurekalert.org/pub_releases/2013-10/f-nfp092513.php

Study: http://journal.frontiersin.org/article/10.3389/fpls.2013.00344/full