With all respect to the author of this research and article in Science, I would like to express my appreciation of what microRNA's have done in jawless vertebrates. They have managed to tip the scale of mono and paraphyl to one side.
This may be the way forward in in our closely related cichlids, microRNA's may be able to decipher the relationships.
Hastings
========
Genetic evidence is laying to rest a long-standing argument over the evolution of jawless vertebrates -- hagfish and lampreys -- and providing insights regarding the common ancestor of all vertebrates.
For years, biologists have debated the origins of jawless vertebrates -- molecular biologists have argued that molecular evidence shows they are each other's closest relatives, while morphologists maintained that detailed anatomical features suggest lampreys were more closely related to jawed vertebrates.
In the most recent study, published Monday (18 October) in Proceedings of the National Academy of Sciences (PNAS), scientists on opposite sides of the argument looked at microRNA data, and found jawless vertebrates are indeed monophyletic, meaning they evolved from a common ancestor not shared by jawed vertebrates.
"I was staggered by this paper," said Philippe Janvier, a paleontologist at the Muséum National d'Histoire Naturelle in Paris, France, and a long time supporter of the idea that lampreys were more closely related to jawed vertebrates. "It's very hard for me to recognize that I've been wrong in my assumption," said Janvier, who did not participate in the research, but this paper provides "very, very strong support for the monophyly -- the common origin of lampreys and hagfishes apart from the origin of the jawed vertebrates."
Biologists originally classified lampreys and hagfish (cyclostomes) as part of a single group due to their gross anatomical similarities -- they were both eel-like creatures that lacked jaws. But more detailed morphological analyses in the 1970s suggested that lampreys were actually more closely related to jawed vertebrates, and hagfish were more primitive. This idea dominated the field until the early 1990s, when molecular evidence once again placed lampreys and hagfish together on the evolutionary tree. Over the next two decades, more and more molecular data emerged to support this monophyly hypothesis, but many morphologists continued to argue that lampreys were more similar to jawed vertebrates.
To resolve the debate, paleontologist Kevin Peterson of Dartmouth College and his colleagues turned to a new source of data -- microRNA. They created small RNA libraries for two different lamprey species, a hagfish, and a catshark (a jawed vertebrate). The team found all but two of the 46 miRNAs found in lampreys and jawed vertebrates in hagfish as well. Furthermore, they found four miRNA families unique to hagfish and lampreys, supporting the idea that the two groups are monophyletic.
"This adds a third type of data, [and] it does come down firmly on the side of cyclostome monophyly," said zoologist Sebastian Shimeld of the University of Oxford, who was not involved in the work.
This was no surprise to Peterson, who was already convinced of this conclusion by the molecular data. But his colleague and coauthor Phil Donoghue of the University of Bristol had been a strong proponent of the opposing view. Upon seeing the miRNA results, he decided to reanalyze the seemingly contradictory morphological data. Compiling all the data previously used to support the paraphyly hypothesis, that lampreys should be lumped with jawed vertebrates, and eliminating obsolete or inaccurate data, the analysis revealed inconclusive results.
"Lo and behold there really is no signal for paraphyly in phylogeny," Peterson said. Between the molecular data, the new miRNA analysis, and "especially with Phil's reanalysis of the morphology, I think you'd be hard pressed to assert strongly that cyclostomes are not monophyletic."
The results could indicate that the common ancestor to vertebrates is more complex than previously believed, Peterson added. If lampreys were more closely related to jawed vertebrates, and hagfish were basal to both groups, one could imagine "a successive building of the vertebrate body plan," Peterson explains -- "you start simple and then you make it more complex." If, on the other hand, lampreys are more closely related to hagfish, the last common ancestor of vertebrates most likely had all the derived characters still found in lampreys and jawed vertebrates, and hagfish simply lost some of these traits after they split from lampreys.
"I think [this study] is the tipping point where the vast majority of new researchers and some of the old morphologists will start to believe" that lampreys and hagfish form a single group, said evolutionary biologist Jon Mallatt of Washington State University, who did not participate in the research.
A.M. Heimberg, et al., "microRNAs reveal the interrelationships of hagfish, lampreys, and gnathostomes and the nature of the ancestral vertebrate," PNAS, www.pnas.org/cgi/doi/10.1073/pnas.1010350107, 2010.
Read more: Jawless evolution explained - The Scientist - Magazine of the Life Sciences http://www.the-scientist.com/news/display/57752/#ixzz137Ev5y83
Friday, October 22, 2010
Wednesday, November 4, 2009
MUTATIONS RESPONSIBLE FOR ENVIRONMENTAL ADAPTATIONS
MUTATIONS RESPONSIBLE FOR ENVIRONMENTAL ADAPTATIONS
While my blog is rooted on Lake Malawi cichlids biodiversity, sometimes I find stories which are indirectly related to the issue of rapid radiation of Lake Malawi cichlids. As we may all know the puzzle in cichlid evolution is to solve the oring of this stunning biodiversity of Lake Malawi. Among the factors responsible for this puzzle are mate choice basing on the male breeding colour morphs. Today, the study in bacteria has managed to locate the mutations which are responsible for phenotypic changes due to environment. In simplistic sense, think of colour morphs in cichlids and water levels or environment or geographic locations in Lake Malawi, is it possible to indetify the mutations responsible?? Think of red tops (P. zebra), blue tops (P. zebra), blue black tops (P. zebra) and C. afra. Is it possible to locate the mutations responsible??
Now read on the story below:
==============================
Researchers for the first time have tracked the specific genetic mutations -- occurring over just a few generations -- that allow bacteria to respond to environmental changes, they report online in Nature today (November 4).
"We showed how evolution happens in real time," said Hubertus Beaumont, a biologist from Leiden University in the Netherlands and first author on the study.
Studies have shown bacteria and other organisms can switch back and forth between phenotypes to better survive in new environments. For instance, Beaumont said, many bacteria switch their surface antigens when invading a host, so they can avoid being attacked, and certain desert plants are programmed to germinate seeds at random time intervals, increasing their chances of encountering rain. "This bet-hedging strategy is very simple, but captures the essence of evolution." Beaumont said. "Natural selection in these uncertain environments causes an organism to evolve protective traits." Exactly how such phenotypic adaptability emerges, however, was unknown.
In order to observe how bet-hedging evolves, Beaumont and his colleague Paul Rainey at Massey University in New Zealand observed Pseudomonas fluorescens, a common rod-shaped bacterium, in a new type of environment. They already knew that the bacteria grow well in a test tube that's shaken manually or in an incubator that allows oxygen to circulate in the culture. So instead of shaking the test tube, a condition to which the bacteria are well-adapted, the researchers watched the bacteria grow in non-shaken test tubes.
As expected, some of the bacteria adapted to the novel environment, forming colonies with an advantageous "wrinkly" morphology as opposed to the ancestral bacteria, which grew smoothly. The team identified these new colony types in the test tube and transferred them to fresh tubes, repeating this process 15 times to select for the new variations. Eventually, the bacteria evolved the ability to rapidly switch their phenotypes between the "wrinkly" and "smooth" cell-types to prepare themselves to cope with the different environments.
"I find these results really intriguing," said Martin Ackermann, an environmental microbiologist at Eidgenössische Technische Hochschule Zurich (or ETH Zurich) in Switzerland who was not involved in the research. "It is amazing to see that phenotypic switching can evolve so rapidly, in the course of a just a few rounds of selection. As far as I know, this has not been observed before."
Beaumont and Rainey then sequenced the evolved bacterial genome and found all the mutations that had arisen and that might have contributed to this new trait. The team identified nine mutations distinguishing bet-hedgers from their ancestors. They pinpointed one specific mutation as the one which allows the phenotype to switch back and forth between different morphologies, while the other mutations, they found, were essential for growing the new type of bacteria.
"It's yet another beautiful study at multiple levels from Paul Rainey's team," said Richard Lenski, a microbial ecologist at Michigan State University who didn't participate in the research, in an email. "This is a neat demonstration that the evolution of bet-hedging was contingent on other mutations that had occurred earlier in the lineage." These earlier changes improved the fitness of the bacteria at each stage.
"The results thus suggest that phenotypic switching is a strategy that can readily evolve," and may capture the earliest evolutionary solutions to life in fluctuating environments, Ackerman wrote in an email.
While my blog is rooted on Lake Malawi cichlids biodiversity, sometimes I find stories which are indirectly related to the issue of rapid radiation of Lake Malawi cichlids. As we may all know the puzzle in cichlid evolution is to solve the oring of this stunning biodiversity of Lake Malawi. Among the factors responsible for this puzzle are mate choice basing on the male breeding colour morphs. Today, the study in bacteria has managed to locate the mutations which are responsible for phenotypic changes due to environment. In simplistic sense, think of colour morphs in cichlids and water levels or environment or geographic locations in Lake Malawi, is it possible to indetify the mutations responsible?? Think of red tops (P. zebra), blue tops (P. zebra), blue black tops (P. zebra) and C. afra. Is it possible to locate the mutations responsible??
Now read on the story below:
==============================
Researchers for the first time have tracked the specific genetic mutations -- occurring over just a few generations -- that allow bacteria to respond to environmental changes, they report online in Nature today (November 4).
"We showed how evolution happens in real time," said Hubertus Beaumont, a biologist from Leiden University in the Netherlands and first author on the study.
Studies have shown bacteria and other organisms can switch back and forth between phenotypes to better survive in new environments. For instance, Beaumont said, many bacteria switch their surface antigens when invading a host, so they can avoid being attacked, and certain desert plants are programmed to germinate seeds at random time intervals, increasing their chances of encountering rain. "This bet-hedging strategy is very simple, but captures the essence of evolution." Beaumont said. "Natural selection in these uncertain environments causes an organism to evolve protective traits." Exactly how such phenotypic adaptability emerges, however, was unknown.
In order to observe how bet-hedging evolves, Beaumont and his colleague Paul Rainey at Massey University in New Zealand observed Pseudomonas fluorescens, a common rod-shaped bacterium, in a new type of environment. They already knew that the bacteria grow well in a test tube that's shaken manually or in an incubator that allows oxygen to circulate in the culture. So instead of shaking the test tube, a condition to which the bacteria are well-adapted, the researchers watched the bacteria grow in non-shaken test tubes.
As expected, some of the bacteria adapted to the novel environment, forming colonies with an advantageous "wrinkly" morphology as opposed to the ancestral bacteria, which grew smoothly. The team identified these new colony types in the test tube and transferred them to fresh tubes, repeating this process 15 times to select for the new variations. Eventually, the bacteria evolved the ability to rapidly switch their phenotypes between the "wrinkly" and "smooth" cell-types to prepare themselves to cope with the different environments.
"I find these results really intriguing," said Martin Ackermann, an environmental microbiologist at Eidgenössische Technische Hochschule Zurich (or ETH Zurich) in Switzerland who was not involved in the research. "It is amazing to see that phenotypic switching can evolve so rapidly, in the course of a just a few rounds of selection. As far as I know, this has not been observed before."
Beaumont and Rainey then sequenced the evolved bacterial genome and found all the mutations that had arisen and that might have contributed to this new trait. The team identified nine mutations distinguishing bet-hedgers from their ancestors. They pinpointed one specific mutation as the one which allows the phenotype to switch back and forth between different morphologies, while the other mutations, they found, were essential for growing the new type of bacteria.
"It's yet another beautiful study at multiple levels from Paul Rainey's team," said Richard Lenski, a microbial ecologist at Michigan State University who didn't participate in the research, in an email. "This is a neat demonstration that the evolution of bet-hedging was contingent on other mutations that had occurred earlier in the lineage." These earlier changes improved the fitness of the bacteria at each stage.
"The results thus suggest that phenotypic switching is a strategy that can readily evolve," and may capture the earliest evolutionary solutions to life in fluctuating environments, Ackerman wrote in an email.
Friday, October 23, 2009
Malawi at the root of humankind 6 MYA
Malawi could be the cradle of humankind-researcher
KARONGA, Malawi (Reuters) - The latest discovery of pre-historic tools and remains of hominids in Malawi's remote northern district of Karonga provides further proof that the area could be the cradle of humankind, a leading German researcher said.
Professor Friedemann Schrenk of the Goethe University in Frankfurt told Reuters that two students working on the excavation site last month had discovered prehistoric tools and a tooth of an hominid.
"This latest discovery of prehistoric tools and remains of hominids provides additional proof to the theory that the Great Rift Valley of Africa and perhaps the excavation site near Karonga can be considered the cradle of humankind," Schrenk said.
A hominid is a member of a family of primates which includes humans and their prehistoric ancestors.
The discovery was at Malema excavation site, 10 km (6 miles) from Karonga.
The site also contains some of the earliest dinosaurs which lived between 100 million and 140 million years ago and early hominids believed to have lived between a million and 6 million years ago.
He is leading a team of researchers from Europe and Africa to establish an African center for interdisciplinary studies on mammal and hominid evolution in the southern African nation.
Karonga is about 615 km (380 miles) north of the capital Lilongwe and is near the border with Tanzania.
KARONGA, Malawi (Reuters) - The latest discovery of pre-historic tools and remains of hominids in Malawi's remote northern district of Karonga provides further proof that the area could be the cradle of humankind, a leading German researcher said.
Professor Friedemann Schrenk of the Goethe University in Frankfurt told Reuters that two students working on the excavation site last month had discovered prehistoric tools and a tooth of an hominid.
"This latest discovery of prehistoric tools and remains of hominids provides additional proof to the theory that the Great Rift Valley of Africa and perhaps the excavation site near Karonga can be considered the cradle of humankind," Schrenk said.
A hominid is a member of a family of primates which includes humans and their prehistoric ancestors.
The discovery was at Malema excavation site, 10 km (6 miles) from Karonga.
The site also contains some of the earliest dinosaurs which lived between 100 million and 140 million years ago and early hominids believed to have lived between a million and 6 million years ago.
He is leading a team of researchers from Europe and Africa to establish an African center for interdisciplinary studies on mammal and hominid evolution in the southern African nation.
Karonga is about 615 km (380 miles) north of the capital Lilongwe and is near the border with Tanzania.
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