From ScienceDaily we learn (Apr. 11, 2011),
“A polyploidy event is basically the acquisition, through mutation, of a ‘double dose’ of genetic material,” explained Yuannian Jiao, a graduate student at Penn State and the first author of the study. “In vertebrates, although genome duplication is known to occur, it generally is lethal. Plants, on the other hand, often survive and can sometimes benefit from duplicated genomes.” Jiao explained that, over the generations, most duplicated genes from polyploidy events simply are lost. However, other genes adopt new functions or, in some instances, subdivide the workload with the genetic segments that were duplicated, thereby cultivating more efficiency and better specialization of tasks for the genome as a whole.
Jiao also explained that, although ancient events of polyploidy have been well documented in plant-genome-sequencing projects, biologists had dated the earliest polyploidy event in flowering plants at around 125 to 150 million years ago. “There were hints that even earlier events had occurred, but no good evidence,” Jiao said. “That’s what makes our team’s findings so exciting. We identified at least two major events — one occurring in the ancestor of all seed plants about 320 million years ago, and another occurring in the flowering-plant lineage specifically, about 192 to 210 million years ago. That’s up to 200 million years earlier than such events were assumed to have taken place.”