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An intriguing study involving walking stick insects led by the University of Sheffield in England and the University of Colorado Boulder shows how natural selection, the engine of evolution, can also impede the formation of new species.

The team studied a plant-eating stick insect species from California called Timema cristinae known for its cryptic camouflage that allows it to hide from hungry birds, said CU-Boulder Assistant Professor Samuel Flaxman. T. cristinae comes in several different types -- one is green and blends in with the broad green leaves of a particular shrub species, while a second green variant sports a white, vertical stripe that helps disguise it on a different species of shrub with narrow, needle-like leaves.

While Darwinian natural selection has begun pushing the two green forms of walking sticks down separate paths that could lead to the formation of two new species, the team found that a third melanistic, or brown variation of T. cristinae appears to be thwarting the process, said Flaxman. The brown version is known to successfully camouflage itself among the stems of both shrub species inhabited by its green brethren, he said.

Using field investigations, laboratory genetics, modern genome sequencing and computer simulations, the team concluded the brown version of T. cristinae is shuttling enough genes between the green stick insects living on different shrubs to prevent strong divergent adaptation and speciation. The brown variant of the walking stick species also is favored by natural selection because it has a slight advantage in mate selection and a stronger resistance to fungal infections than its green counterparts.

"This is one of the best demonstrations we know of regarding the counteractive effects of natural selection on speciation," said Flaxman of CU-Boulder's Department of Ecology and Evolutionary Biology, second author on the new study. "We show how the brown population essentially carries genes back and forth between the green populations, acting as a genetic bridge that causes a slowdown in divergence."

A paper on the subject appeared in a recent issue of the journal Current Biology. Other study co-authors were from the University of Sheffield, Royal Holloway University of London, Utah State University, the University of Nevada, Reno and the University of Lausanne in Switzerland.

"This movement of genes between environments slows down the genetic divergence of these stick insect populations, impeding the formation of new species," said Aaron Comeault, a former CU-Boulder graduate student and lead study author who conducted the research while at the University of Sheffield. Comeault is now a postdoctoral researcher at the University of North Carolina at Chapel Hill.

The new results underscore how combining natural history and cutting-edge genetics can help researchers gain a better understanding of how evolution operates in nature. It also shows how natural selection can sometimes promote but other times hinder the formation of new species, according to the research team.

Walking sticks are one of nature's oddest insect groups and range in size from the half-inch long T. cristinae to species in Borneo and Vietnam that are more than a foot long. Most walking sticks rely on plant mimicry to protect them from predators.

Source: University of Colorado at Boulder [August 06, 2015]

Research reveals that large areas of 'degraded' forest in Southeast Asia can play an important role in conserving mammal diversity.

Mammals can be one of the hardest-hit groups by habitat loss, and a lot of research has been carried out to find the best ways to conserve mammal diversity.

Much of this research has focused on very large-scale changes in land use and the impacts this will have on overall mammal diversity. However, many important decisions about land use are made at much more local scales, for example at the level of individual landowners.

Now, in a detailed study led by Imperial College London that looked at mammal diversity across different small-scale landscapes in Borneo, researchers have identified previously logged forests as an overlooked source of refuge for mammals.

These 'selectively logged' forests, where only certain tree species are removed, are often considered to be degraded and are frequently cleared to make way for plantations. The new results, published in the >journal Ecological Applications, suggest they should be better protected.

The team recorded mammals using trap-and-release techniques and motion-sensing cameras over three years, creating an unprecedented 20,000 records of species in three land-use types: old-growth forest, logged forest and oil palm plantation. This is one of the most intensive studies of rainforest mammal diversity ever undertaken.

To their surprise, they found that mammal diversity for large mammals, like the clouded leopard and civets, was similar for both old-growth forests and logged forests. For small mammals, such as squirrels and rodents, the diversity was actually higher in logged forests.

Both sizes of mammals however suffered heavy losses of diversity in oil palm plantations. Most species discovered on the plantations likely spilled over from adjoining forests or riparian zones -- strips of forests surrounding rivers to reduce the chance of flooding.

Lead researcher Dr Oliver Wearn, who completed the research for his PhD in the Department of Life Sciences at Imperial, said that the surprise result that mammal diversity remains high in logged forests may be because of the way habitats are distributed.

"The logging process creates a greater variation in habitat types in a smaller area, from untouched areas on steep slopes to completely denuded areas of open grassland. Old-growth forests would likely have the same diversity if we looked at them on a much larger scale."

Dr Wearn also stresses that while a greater diversity is recorded now in these logged forests, it cannot yet be certain that this diversity will remain in the future as the knock-on effects of habitat loss take effect on mammals and other rainforest species.

He added: "What we can say from this study is that protecting those large areas of forest that have already been logged could help conserve mammal species better than preserving fragmented pockets of forests inside oil palm landscapes."

This study complements another recent study from Imperial, where researchers recommended rehabilitating logged forests as a way to prevent highly threatened species from becoming extinct.

"Where old growth forests remain, however, these are still the best habitats for mammals and other native species, and should be the absolute top priority for conservation," said Dr Wearn.

Author: Hayley Dunning | Source: Imperial College London [August 22, 2016]

The Piltdown Man scandal is arguably the greatest scientific fraud ever perpetrated in the UK, with fake fossils being claimed as evidence of our earliest ancestor.

Published 100 years on from Dawson's death, new research reveals that the forgeries were created using a limited number of specimens that were all constructed using a consistent method, suggesting the perpetrator acted alone.

It is highly likely that an orang-utan specimen and at least two human skeletons were used to create the fakes, which are still kept at the Natural History Museum.

Between 1912 and 1914 Museum palaeontologist Arthur Smith Woodward and the amateur antiquarian Charles Dawson announced the discovery of fossils from Piltdown in Sussex. These were supposedly a new evolutionary link between apes and humans. They indicated a species with both an ape-like jaw and a large braincase like a modern human. Before he died in 1916, Dawson claimed to have discovered further evidence at a second site.

The forgeries helped misdirect the study of anthropology for decades. While doubts were raised from the start, it took 40 years for the scientific community to recognise that the remains had been altered to seem ancient and had been planted in the sites.

The new research, published in >Royal Society Open Science, was undertaken by a multi-disciplinary team from institutions in Liverpool, London, Cambridge and Canterbury. They used the latest scientific methods to test the Piltdown specimens to uncover more about how the forgery was done.

DNA analyses show that both the canine from the first Piltdown site and the molar from the second site probably came from one orang-utan, related most closely to orang-utans now occupying south-west Sarawak (Borneo). In addition, the shape and form of the molar from the second Piltdown site was almost certainly from the other side of the jawbone planted in the first site.

3D X-ray imaging (Micro-CT scans) show that many of the bones and a tooth were filled with Piltdown gravel and the openings plugged with small pebbles. Holes in the skull bones were filled with dental putty, which was also used to re-set the teeth in the jaw and to reconstruct one of the teeth that fell apart while it was being ground down.

Dr Laura Buck co-author on the paper from the Division of Biological Anthropology, University of Cambridge commented on the project's importance. "Even today, over a hundred years after the Piltdown fraud was perpetrated, it remains relevant because of the huge impact it had on the course of Palaeoanthropological research at the beginning of the twentieth century."

"Fossil human remains from Africa, such as the Taung child from South Africa, were largely ignored when first found because they didn't fit with preconceptions of what an early human relative would look like, based on Piltdown Man. This serves as an important reminder to researchers today to study what is there and not what we think should be there," Buck said.

Dr Isabelle De Groote from Liverpool John Moores University and lead author on the paper, thinks the results point to a clear conclusion: "Although multiple individuals have been accused of producing the fake fossils, our analyses to understand the modus operandi show consistency between all the different specimens and on both sites. It is clear from our analysis that this work was likely all carried out by one forger: Charles Dawson."

Source: University of Cambridge [August 11, 2016]