BLOOMINGTON, Ind. -- Extra genomes appear, on average, to offer no benefit or disadvantage to plants, but still play a key role in the origin of new species, say scientists from Indiana University Bloomington and three other institutions in this week's Proceedings of the National Academy of Sciences.
Plant biologists have long suspected polyploidy -- the heritable acquisition of extra chromosome sets -- was a gateway to speciation. But the consensus was that polyploidy is a minor force, a mere anomaly that accounts for 3 or 4 percent of the world's flowers and ferns.
The first direct, comprehensive survey of polyploid speciation in plant evolution severely challenges that notion.
"In the present paper, we make it clear that it is a common process," said evolutionary biologist and lead author Troy Wood, who began the research during graduate training at IU Bloomington. "Fifteen percent of flowering plant species and almost a third of fern species are directly derived from polyploidy."
Wood is now a research scientist at University of Muenster in Germany.
Could polyploidy provide plants with a powerful advantage over their chromosome-challenged peers? Not necessarily. The scientists' exhaustive survey of published phylogenetic and genomic data also shows that plant lineages starting with a polyploid ancestor appear to be no more successful at spawning species than diploid plants, which have two sets of chromosomes.
"The fact that polyploidy seems to have no effect on diversification rates should reduce the number of enthusiastic commentaries about the 'advantages of polyploidy,'" said IU Bloomington evolutionary biologist and paper coauthor Loren Rieseberg, who supervised the research. "However, our diversification rate analyses only examined recent polyploids. A future area of research should be to ask whether more ancient polyploidy events have increased diversification rates."
|Contact: David Bricker|