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'Everything is interrelated' say genetic scientists

Tree of life's family tree

Scientists have written the family tree for the tree of life.

Researchers from around the world and several Canadian universities say it's taken nine years of work to analyze the genetics of 1,100 plant species from algae to elm trees. That work, released Wednesday in the journal Nature, has allowed them to pinpoint a billion years of evolutionary relationships between plants as different as cannabis and cucumbers, orchids and oaks.

"Everything is interrelated," said the University of Alberta's Gane Wong, one of the paper's dozens of co-authors.

Science has known for a long time that species with significant differences can be related through a common evolutionary ancestor. In plants, those relationships have been studied mostly through how they look or behave. Do they have trunks? Flowers? How do their seeds form?

Wong and his colleagues — nearly 200 of them — have been looking at how the links are expressed through genetics.

They isolated and sequenced genetic RNA material from 1,124 different plant species. They took care to select a wide variety of plant types and not to focus on species, such as cereal crops, important to humans.

"We wanted to look at how plants evolved," said Wong. "This is going all the way back to algae.

"One of the things biologists constantly argue over is which came before what. How did this species evolve?"

New species are created when a mutation begins splitting one species into two. Eventually, the two themselves mutate, which leads to another two, and so on, until there's a vast branching tree of life with a half-million different plant species in it.

Wong and his colleagues wondered if the record of those ancient mutations would be preserved in the RNA.

"Can we, from the RNA sequence, draw this tree of life for all 1,000 species?" asked Wong. "For 95 per cent or so, the answer is, yes, we can do it quite well and probably better than you could do by just looking."

The computing power needed to resolve that much information was significant. Data to be analyzed was measured in terabytes, where one terabyte equals a million million bytes.

Even then, the team couldn't resolve everything. They couldn't find branches in the tree for about five per cent of species, either because there wasn't enough data or because it dated from so long ago it couldn't be read accurately.

"We're talking about events that happened a billion years ago."



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