Gehyra rohan: A new species of Gecko from the Bismarck Arichipelago..

The Bismark Archipelago is a large group volcanic islands to the east of Papua New Guinea. This wide scatting of mostly small oceanic islands is a biodiversity hotspot, with each island typically having its own flora and fauna descended from small numbers of individuals that managed to reach the islands after they rose from the sea. Despite this importance, the remote nature of the islands means that many are relatively unexplored by biologists, and the discovery of even quite large animals there is not unusual.

In a paper published in the journal Zootaxa on 14 December 2016, Paul Oliver of the Division of Evolution, Ecology and Genetics, Research School of Biology, and Centre for Biodiversity Analysis at The Australian National University, Jonathan Clegg of Aquatic and Terrestrial Ecology at the Royal Belgian Institute of Natural Sciences and the Biodiversity Inventory for Conservation, Robert Fisher of the Western Ecological Research Center of the U.S. Geological Survey, Stephen Richards of the South Australian Museum and Peter Taylor and Merlijn Jocque, also of Aquatic and Terrestrial Ecology at the Royal Belgian Institute of Natural Sciences and the Biodiversity Inventory for Conservation describe a new species of Gecko from the Bismarck Archipelago.

The new species is placed in the genus Gehyra, which has previously been recorded from Southeast Asia east to the Ryukyu Islands and southeast to the islands of Melanesia and Oceania, and given the specific name rohan, which is the local name in the Nali language given to the species on Manus Island in the Admiralty Islands, a name requested by the people of Sohoniliu Village on Manus Island. The species is exceptionally large, reaching 130-150 mm in length, and brown in colour and mottled with patches of lighter brown, white, black and orange.

Specimen of Gehyra rohan from Mussau Island in the St Matthias Islands. S. Venter in Oliver et al. (2016).

The species was found at a number of separate localities on Manus Island in the Admiralty Islands, as well as possibly on the neighbouring islands of Los Negros and Nauna. It was also found on Mussau Island in the St Matthias Islands, and possibly Fiji. The species was found in both primary and disturbed lowland rainforest, living primarily in the trees, though the species was also found in and around Human habitations and in one case in a cave. One specimen was observed to 'glide' about 3 m to another tree when disturbed.

A molecular phylogenetic study suggests that Gehyra rohan is most closely related to Gehyra georgepottshaasti, a species found on Vanuatu, and Gehyra vorax, a species found in Fiji, but that it probably diverged from these species during the late Miocene; earlier than some estimates for the emergence of the Admiralty Islands, Fiji or Vanuatu. This suggests that the genus Gehyra has been in the region since at least the Miocene, possibly occupying a series of now vanished volcanic islands prior to the emergence of the modern islands.

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Identifying Archaic Human DNA in gene sequences from modern Melanesians.

Modern DNA recovery techniques have allowed scientists to recover genetic sequences from a number of Neanderthal individuals (members of a fairly well known Archaic Human population found in Europe and West Asia before about 40 000 years ago) as well as some Denisovans (members of a poorly understood Archaic Human population found in Central Asia before about 50 000 years ago). This has led to the discovery of genetic material derived from these ancient populations within many modern Human groups, and, more recently, attempts to determine what genes preserved from Archaic Human groups might contribute to modern Humans. Such studies have found evidence of Neanderthal DNA in all non-African modern populations, while Denisovan DNA has been found only in Melanesian populations.

In a paper published in the journal Science on 17 March 2016, a team of scientists led by Benjamin Vernot of the Department of Genome Sciences at the University of Washington present the results of a study of the genomes of 1523 modern Humans from around the globe, including 35 Melanesians from Papua New Guinea and the Bismarck Archipelago, and attempt to analyse the preserved DNA sequences in these individuals.

Melanesian genomic variation in a global context. (A) Locations of the 159 geographically diverse populations studied. Information on the Melanesian individuals sequenced (blue triangles) is shown in the inset. Vernot et al. (2016).

All Humans, including Archaic populations such as Neanderthals and Denisovans, share almost all of their DNA. In this context 'Neanderthal DNA' or 'Devisovan DNA' refers to variable alleles found in the ancient population, but not in modern African populations not thought to share any genetic heritage since the ancestors of these groups left Africa in the Middle Pleistocene.  An allele is one of two or more different genes that can occur at a gene locus, for example different alleles for blue or brown eyes may be found at the gene locus for eye colour in Humans

The highest proportion of Neanderthal DNA was found in modern East Asians, with Europeans having a slightly lower level and South Asians a slightly lower level still. The proportion of Neanderthal found in Melanesians was much lower (roughly half) than that found in any of these groups, but still much larger than the highest found in any African group (people from the Western Division of The Gambia).

Only Melanesians were found to have significant levels of Denisovan DNA (trace amounts were found in samples from East and South Asians), who had slightly higher levels of Denisovan DNA than they did Neanderthal DNA - though the combined level of Denisovan and Neanderthal DNA found in Melanesians was slightly higher than that found in East Asians.

The areas of DNA from Archaic populations were not random, but rather similar sections of Archaic DNA appear to have been retained in different populations. This suggests that some Archaic DNA alleles were strongly selected against in the ancestors of modern humans, while others appear to have been more useful. In particular Vernot et al. note that a section of Archaic DNA alleles in an area of chromosome 7 associated with language skills has been lost in all modern Humans. Conversely a number of Archaic alleles associated with the metabolism have been retained in different modern Human populations, including genes associated with glucose metabolism and lipid processing. A number of genes associated with the immune system have also been conserved.

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Genetic data from two new Denisovan individuals.                                                                 The Denisonvans were an ancient people who are known from only a single archaeological site, a cave...

Neanderthal DNA from a 37 000-42 000 modern Human jaw from Romania.     Neanderthals first appeared in Europe around 300 000 years ago and were replaced by anatomically modern Humans between 45 000 and 35 000 years ago. Genetic studies if modern Human populations show that almost all non-Africans have traces of Neanderthal...

Human remains from the Middle Pleistocene of Normandy.                                                                Early and Middle Pleistocene Human remains are extremely rare in northern Europe, having to date...

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