Silver Cords: The millennial journey of a species

Friday, December 13, 2013

The millennial journey of a species

Having evidence of the past is essential to preserve human culture. The evidence of the past can be stored in digital or analog format , by photography or family trees . However, these tools are often not very useful if we want to explore our history for centuries or millennia ago .

Fortunately, science has discovered two ways to approximate the time objects , organisms or prehistoric remains . The first technique uses radioactive atoms. Not many people know that nearly all matter ( including agencies ) has a tiny number of atoms over time, to emit radioactivity , are converted into other chemical elements. Scientists have measured accurately how quickly this change occurs , which serves as a natural clock.
For example , 50% of the atoms of the radioactive isotope carbon-14 5.730 years slow switching to nitrogen - 14 when an organism dies . Therefore, if measured a wooden statuette has 25% of the amount of carbon -14 would have a living organism , it can be inferred that the tree from which the wood came was cut about 11.460 years ago.
The second technique has a genetic basis and reveals when two species had a common ancestor. For example , if an earthquake crack to an island in two million years after the bodies of the two new islands , having no contact, evolve on their own to create new species. By comparing the genetics of two new species , scientists can approach the time when the island was separated and when there was the ancestor of those species.
This technique of measuring genetic fail two curious facts of nature . First is that the deoxyribonucleic acid or DNA , the genetic material that determines whether we are human , chickens or tomatoes , random changes very slowly , so it can be estimated statistically how many thousands or millions of years a number of mutations were slow to occur .
Second is that in sexual reproduction , the DNA of the father and the mother is mixed to create a unique DNA in the progeny . Certain types of DNA are transmitted , without mixing , directly through the stem . This DNA , called mitochondrial DNA , is perfect for studying the past of organisms.
Scientists Alondra Diaz- Lameiro , Taras Oleksyk , Fernando Bird- Pico and Juan Martinez - Cruzado, all of the Department of Biology of the Mayagüez Campus of the University of Puerto Rico , the study used mitochondrial DNA to study different species of the genus salamanquitas Sphaerodactylus . The team studied species living in Puerto Rico , Mona, Desecheo and Dominican Republic with the intention of solving the mystery of endemic salamanquitas Mona and Desecheo. Although it is believed they came to these two islands floating in vegetative matter (either as adults or eggs) and eventually became independent species , do not know when they arrived, or if floated from Puerto Rico or Dominican Republic .
Scientists tracked 113 salamanquitas of 14 different species at various locations in Puerto Rico , Desecheo , Mona and Dominican Republic . After obtaining his DNA , this genetic material was analyzed in the laboratory to determine how many had mutations in mitochondrial DNA . A smaller number of mutations are more genetically different species nearby .
Scientists discovered that the gecko Desecheo ( Sphaerodactylus levinsi ) is more related to Mona ( Sphaerodactylus monensis ) and this in turn has its most recent ancestors in a population of the species guaniquenses salamanquitas Sphaerodactylus nicholsi . The other species of Puerto Rico are not as genetically related to the previous three species. That is 30 miles Desecheo and Mona Mona 40 miles from Puerto Rico makes these trips of a salamanquitas almost unbelievable .
In addition, scientists found that salamanquitas of Dominican Republic are genetically more distant local salamanquitas , which reinforces the hypothesis that salamanquitas reached Mona and Desecheo floating from Puerto Rico , as winds and currents flowing southeast to northwest .
Mitochondrial DNA analysis also revealed that salamanquitas Desecheo from Mona reached approximately 2.6 million years ago from Guánica and Mona about 3 million years ago . The first salamanquitas came to Puerto Rico about 11 million years ago .
One aspect that helped the salamanquitas were successful in colonizing the islands of Mona and Desecheo was that its climate was quite similar to Guanica, which were more or less used .
The author is Associate Professor in Physics and Science Education at Morehead State University and a member of Puerto Rico Science ( www.cienciapr.org ) .

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