Study Suggests European wipe-out of early Americans

The first large scale study of ancient DNA from early American people has confirmed the devastating impact of European colonisation on the Indigenous American populations of the time.

According to the study, a striking absence of the pre-Columbian genetic lineages in modern Indigenous Americans, showing extinction of these lineages with the arrical of the Spaniards. None of the genetic was found in almost 100 ancient humans were present or showed evidence of descendants in today's Indigenous populations. The separation appears to have been established as early as 9000 years ago and was completely unexpected, so the scientists were examined many demographic scenarios to try and explain the pattern. The only scenario that fit the observations was that shortly after the initial colonisation, populations were established that subsequently stayed geographically isolated from one another and that a major portion of these populations later became extinct following European contact. This closely matches the historical reports of a major demographic collapse immediately after the  the Spaniards arrived in the late 1400s

The ancient genetic signals also provide a more precise timing og the first people entering the Americas - via the Beringian land bridge that connected Asia and the north-western tip of North America during the last ICe Age.

Soruce: Science Advances

Tiger-spray DNA shown as valuable conservation tool

Scientists have demonstrated a new technique to non-invasively survey tigers using their scent sprays, which are detected much more frequently in the wild than scat--the 'breadcrumb' that researchers have traditionally used to track the endangered animals. The findings show that DNA taken from tiger spray is just as good or even better than scat in identifying individual tigers and their gender, and have the potential to increase the power of conservation surveys and management. 

"Genetic monitoring of tiger source populations is a conservation priority," said Anthony Caragiulo, a postdoctoral researcher in the American Museum of Natural History's Sackler Institute for Comparative Genomics. "The utility of this new method is really impactful because it will let us dramatically build upon the number of tigers that can be surveyed and, consequently, increase our understanding of these elusive animals--hopefully before they are gone."

Despite intense conservation efforts, there are fewer than 3,200 tigers (Panthera tigris) in the wild, living in less than seven percent of their historical range. When a population is confined to small islands of wilderness, as are tigers, there is a higher risk of inbreeding and loss of genetic diversity, leaving the species with weaker young. To combat this, the Museum has been working with the global wild-cat conservation organization Panthera to establish "genetic corridors" that allow tigers to seek new territory for prey and new populations for breeding. "Tracking" individual cats using genetic markers lets researchers map movement within and between populations.

Genetic tracking has traditionally relied on extracting DNA from scat collected in the wild. But in humid, tropical landscapes--like those in Sumatra, where a number of tigers live--scat often degrades before researchers can find it. Scent sprays left by tigers on trees and overhanging leaves degrade less quickly, and can be detected by researchers between two and eight times as frequently as scat. So, to boost the effectiveness of genetic monitoring of tigers in warm regions, the research team questioned whether DNA could be extracted from sprays.

The researchers collected spray samples from three captive tigers in Ontario with cotton swabs that were then stored in tubes of buffer to help preserve the DNA. Tiger spray is a combination of anal gland secretions--said, surprisingly, to have a floral scent like citrus--and urine, which contains DNA in the form of cells from the urethra. The researchers were able to amplify microsatellite loci, which are noncoding DNA sequences with unique numbers of repeated nucleotides providing enough information to "fingerprint" individual tigers, and portions of the sex chromosome to determine whether they are male or female.

"We recently spent weeks looking for tiger scat in the field with very little luck," said Rob Pickles, monitoring specialist for Panthera. "Although this new spray technique wouldn't replace scat studies entirely, we now know that we can use both methods in conjunction to drastically increase our monitoring abilities."

The next step for the researchers is to test the technique in the field, where it also could be used to monitor other scent-spraying animals, like lions.

This Story is taken from Science Daily

Ancient DNA extracted from extinct Giant kangaroos

A team of scientists led by Dr Bastien Llamas and Professor Alan Cooper from the University of Adelaide's Australian Centre for Ancient DNA (ACAD) have extracted DNA sequences from two species: a giant short-faced kangaroo (Simosthenurus occidentalis) and a giant wallaby (Protemnodon anak). These specimens died around 45,000 years ago and their remains were discovered in a cold and dry cave in Tasmania.

Dr Bastien Llamas with a skull of an extinct short-faced kangaroo (Simosthenurus occidentalis)

From the out come of this research work it is found that the extinct giant wallabies are very close relatives of large living kangaroos, such as the red and western grey kangaroos. Their skeletons had suggested they were quite primitive macropods─a group that includes kangaroos, wallabies, pademelons and quokka.

The research has also confirmed that short-faced kangaroos are a highly distinct lineage of macropods, which had been predicted on their unusual anatomy.

In addition to poor DNA preservation, most of the extinct Australian megafauna do not have very close relatives roaming around today, which makes it more difficult to retrieve and interpret the genetic data.

Although ancient DNA confirms that the short-faced kangaroos left no descendants, it also shows their closest living cousin could be the banded hare-wallaby (Lagostrophus fasciatus), which is now restricted to small isolated islands off the coast of Western Australia.

The research is published online (ahead of print) in Molecular Biology and Evolution.

Source: Science Daily