PROVIDENCE, R.I. [Brown University] Just as a company creates new, better versions of a product to increase market share and pad its bottom line, an international team of researchers led by Brown University has found that plants tinker with their design and performance before flooding the environment with new, improved versions of themselves.
The issue: When does a grouping of plants with the same ancestor, called a clade, begin to spin off new species? Biologists have long assumed that rapid speciation occurred when a clade first developed a new physical trait or mechanism and had begun its own genetic branch. But the team, led by Brown postdoctoral research associate Stephen Smith, discovered that major lineages of flowering plants did not begin the rapid spawning of new species until they had reached a point of development at which speciation success and rate would be maximized. The results are published in the American Journal of Botany.
"Evolution is not what we previously thought," said Smith, who works in the laboratory of Brown biologist Casey Dunn. "It's not as if you get a flower, and speciation (rapidly) occurs. There is a lag. Something else is happening. There is a phase of product development, so to speak."
To tease out the latent speciation rate, Smith and colleagues from Yale University and the Heidelberg Institute for Theoretical Studies in Germany compiled the largest plant phylogeny to date, involving 55,473 species of angiosperms (flowering plants), the genealogical line that represents roughly 90 percent of all plants worldwide. The group looked at the genetic profiles for six major angiosperm clades, including grasses (Poaceae), orchids (Orchidaceae), sunflowers (Asteraceae), beans (Fabaceae), eudicots (Eudicotyledoneae), and monocots (Monocottyledoneae). Together, these branches make up 99 percent of flowering plants on Earth.
The common ancestor for the branches is Mesangiospermae, a clade th
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