Protein sequencing memecahkan misteri Darwin untuk mamalia aneh Amerika Selatan--T-REC-komunitas reptil-semarang--KSE-komunitas satwa eksotik

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Protein sequencing memecahkan misteri Darwin untuk  mamalia aneh Amerika Selatan

Para ilmuwan telah selesaikan potongan teka-teki evolusi hampir 200 tahun yang mengelilingi kelompok mamalia yang Charles Darwin sebut " binatang aneh yang pernah ditemukan . " Penelitian baru menunjukkan bahwa ungulates atau hooved di Amerika Selatan - yang terakhir  hilang  10.000 tahun yang lalu - sebenarnya terkait dengan mamalia seperti kuda daripada gajah dan spesies lain dengan ikatan evolusi kuno ke Afrika ...read more

Protein
sequencing solves Darwinian mystery of strange South American mammals

Date:

March 18, 2015

Source:

University of York

Summary:

Scientists have
resolved pieces of a nearly 200-year-old evolutionary puzzle surrounding the
group of mammals that Charles Darwin called the "strangest animals ever
discovered." New research shows that South America's native ungulates, or
hooved mammals -- the last of which disappeared only 10,000 years ago -- are
actually related to mammals like horses rather than elephants and other species
with ancient evolutionary ties to Africa as some taxonomists have maintained.

.......................

scientists have resolved
pieces of a nearly 200-year-old evolutionary puzzle surrounding the group of
mammals that Charles Darwin called the "strangest animals ever
discovered." New research led by the Natural History Museum, the American
Museum of Natural History and the University of York shows that South America's
native ungulates, or hooved mammals -- the last of which disappeared only
10,000 years ago -- are actually related to mammals like horses rather than
elephants and other species with ancient evolutionary ties to Africa as some
taxonomists have maintained. Published today in the journal Nature,
the findings are based on fossil protein sequences, which allow researchers to
peek back in time up to 10 times farther than they can with DNA.

Ian Barnes, Research Leader at the Natural History Museum and one of the
paper's authors, explained: "Although the bones of these animals had been
studied for over 180 years, no clear picture of their origins had been reached.
Our analyses began by investigating ancient DNA to try to resolve the
problem."

"Fitting South American ungulates to the mammalian family tree has
always been a major challenge for palaeontologists, because anatomically they
were these weird mosaics, exhibiting features found in a huge variety of quite
unrelated species living all over the place," said Ross MacPhee, one of
the paper's authors and a curator in the American Museum of Natural History's
Department of Mammalogy. "This is what puzzled Darwin and his collaborator
Richard Owen so much in the early 19th century. With all of these conflicting
signals, they couldn't say whether these ungulates were related to giant
rodents, or elephants, or camels -- or what have you."

However, the team soon realized that ancient DNA -- that is, genetic
material extracted from fossils -- did not survive in these fossils, because
the DNA molecule survives poorly in the warm, wet conditions like those typical
of South America. The breakthrough came when the researchers switched to
analysing collagen, a structural protein found in all animal bones that can
survive for a million years or more in a wide range of conditions. The chemical
structure of the amino acids that make up a protein is ultimately dictated by
specific coding sequences in the organism's DNA. Because of this key
relationship, amino acid compositions of the same protein in different species
can be analysed and compared, providing insight into how closely the species
are related.

"People have been successful in retrieving collagen sequences from
specimens dating up to 4 million years old, and this is just the start,"
said University of York Professor Matthew Collins, whose lab did the sequencing
work. "On theoretical grounds, with material recovered from permafrost
conditions, we might be able to reach back 10 million years."

The scientists used proteomic analysis to screen 48 fossils of Toxodon
platensis andMacrauchenia patachonica, the very species whose
remains Darwin discovered 180 years ago in Uruguay and Argentina. "By
selecting only the very best preserved bone specimens and with various
improvements in proteomic analysis, we were able to obtain roughly 90 percent
of the collagen sequence for both species," said lead author Frido Welker,
a Ph.D. student at the Max Planck Institute for Evolutionary Anthropology and
the University of York. "This opens the way for various other applications
in paleontology and paleoanthropology, which we are currently exploring."

With modern techniques, the researchers were able to conclusively show that
the closest living relatives of these species were the perissodactyls, the
group that includes horses, rhinos, and tapirs. This makes them part of
Laurasiatheria, one of the major groups of placental mammals. The molecular
evidence corroborates a view held by some leading paleontologists that the
ancestors of these South American ungulates came from North America more than
60 million years ago, probably just after the mass extinction that killed off
non-avian dinosaurs and many other vertebrates.







Story Source:

The above story is based on materials provided by University of York. Note: Materials may be edited
for content and length.







Journal Reference:

1.    Frido Welker, Matthew J. Collins,
Jessica A. Thomas, Marc Wadsley, Selina Brace, Enrico Cappellini, Samuel T.
Turvey, Marcelo Reguero, Javier N. Gelfo, Alejandro Kramarz, Joachim Burger,
Jane Thomas-Oates, David A. Ashford, Peter D. Ashton, Keri Rowsell, Duncan M.
Porter, Benedikt Kessler, Roman Fischer, Carsten Baessmann, Stephanie Kaspar,
Jesper V. Olsen, Patrick Kiley, James A. Elliott, Christian D. Kelstrup,
Victoria Mullin et al. Ancient proteins resolve the evolutionary
history of Darwin’s South American ungulates. Nature, 2015
DOI: 10.1038/nature14249

http://www.sciencedaily.com/releases/2015/03/150318144841.htm

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