BROWN (US) — Just as a company creates new, better versions of a product, plants play around with design and performance before flooding the environment with new, improved versions of themselves.
It has been long assumed that species proliferate soon after plants develop a new physical trait, but a study finds rapid spawning doesn’t begin until plants have achieved an optimal configuration for market success.
The research is reported in the American Journal of Botany.
“Evolution is not what we previously thought,” says Stephen Smith, a postdoctoral research associate who works in the laboratory of Casey Dunn, assistant professor of biology at Brown University.
“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, including 55,473 species of flowering plants (angiosperms), the genealogical line that represents roughly 90 percent of all plants worldwide.
The group looked at the genetic profiles for six groupings of plants with the same ancestor (called a clade), including grasses (Poaceae), orchids (Orchidaceae), sunflowers (Asteraceae), beans (Fabaceae), eudicots (Eudicotyledoneae), and monocots (Monocottyledoneae). Together, these branches make up 99 percent of all flowering plants on Earth.
The common ancestor for the branches is Mesangiospermae, a clade that emerged more than 125 millions years ago. Yet with Mesangiospermae and the clades that spun off it, the boom in speciation did not occur around the ancestral root; instead, the diversification happened some time later, although a precise time remains elusive.
“During the early evolution of these groups,” Smith says, “there is the development of features that we often recognize to identify these groups visually, but they don’t begin to speciate rapidly until after the development of the features.”
The findings are consistent with the view that radiations tend to be lit by a long fuse, and also with the idea that an initial innovation enables subsequent experimentation and, eventually, the evolution of a combination of characteristics that drives a major radiation, the study says.
Triggers for the speciation explosion could be internal, such as building a better flower or learning how to grow faster and thus outcompete other plants. The winning edge could also have come from the arrival of pollinating insects or changes in climate.
To compile the phylogenetic tree, the group combined data from a survey of the peer-reviewed literature with a gene-wide classification of species gathered by GenBank, a genetic sequence database run by the National Institutes of Health.
“This is a nice example of how computer science and cyberinfrastructure initiatives can help to extend the limits of biological explorations,” says Alexandros Stamatakis, group leader of the scientific computing group at the Heidelberg Institute.
The National Science Foundation and the German Science Foundation funded the research. The computations to assemble the phylogeny were performed at Yale’s High Performance Computing Center and at the Texas Advanced Computing Center.
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