Genome complexity: new review of epigenetics studies (Introduction)

by David Turell , Monday, May 01, 2017, 18:33 (2550 days ago) @ David Turell

Up-to-date review of epignetic studies from Reznick onward:

http://www.the-scientist.com/?articles.view/articleNo/49258/title/Evolution-s-Quick-Pac...

"Here was evolution—genetic change at the population level—happening right before Reznick’s eyes.

“'People thought, if we want to understand the process of evolution, we look at the fossil record,” says Reznick, now a biology professor at the University of California, Riverside. But by averaging phenotypic change across tens of thousands or millions of years, the fossil record underestimates rates of change on shorter timescales, so “for a very long time, people were looking at a biased image of how evolution happens.”

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"As Reznick was puddle-jumping across Trinidad, famed husband-and-wife evolutionary biologists Peter and Rosemary Grant in the Galápagos Islands were documenting changes in the size and shape of finch beaks following environmental fluctuations.

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"Within evolutionary biology there really has been an unheralded paradigm shift between 1980 and now,” says Reznick. “Most evolutionary biologists consider it routine to think of evolution as a contemporary process.”

"The concept, appropriately termed contemporary evolution, is now well accepted, agrees Stephen Ellner, an ecologist and evolutionary biologist at Cornell University. “At this point, there’s a general understanding that this is happening, and it’s happening all over.” The research has now shifted from documenting this phenomenon to studying its consequences.

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"The literature on “rapid evolution” is now 30 years deep. Using what are known as common garden experiments—raising animals from different populations in the same controlled environment (as Reznick did with the guppies)—researchers have observed some astonishing rates. In 1997, Reznick and his colleagues calculated rates of change in his guppy experiments of “up to seven orders of magnitude greater than rates inferred from the paleontological record,” the authors wrote in Science.6 That same year, Harvard University’s Jonathan Losos, then at Washington University in St. Louis, and collaborators published a Nature paper documenting the differentiation of anole populations over a decade and a half following the release of the lizards onto 14 small islands in the Bahamas in 1977 and 1981.

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"In 2011, for example, Reznick worked in collaboration with Martin Turcotte’s group at the University of Pittsburgh to demonstrate that evolving field populations of green peach aphids grew significantly faster and reached higher densities than control populations that could not evolve because they harbored no genetic variation. In 2014, Tim Farkas, a postdoc at the University of Connecticut, reported similar dynamics in experimental populations of stick insects, where the relative fitness of two morphs—equally represented at the outset—varied according to the density of the founding populations.

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"Uusi-Heikkilä knows without more solid fieldwork there’s still a steep hill to climb to convince skeptics; laboratory studies alone just won’t cut it. “I have to be very careful when I mention zebrafish and fisheries in the same sentence,” she admits. “But what we are able to do with this model system and experimental studies is disentangle the plastic and evolutionary effects to show that it is possible. Because I think previously people didn’t even believe this is possible. I mean, evolution can’t happen in a few generations, it’s something that takes millions of years.'”

Comment: Once again we are looking at adaptations, not species change. The fossil record suggests that it happens quickly since we don't find intermediate forms. Is speciation always by saltation? Is there more evolution to come or is the process at an end?