Oct. 14 (UPI) -- For the first time, scientists sequenced the genome of the entire oak family -- surveying the DNA of some 260 oak species. The undertaking revealed the unique history and relationships that define the tree's evolution over the course of 56 million years.
A combination of genomic mapping and fossil data helped scientists trace the tree's diversification back through time. Their efforts could inform conservation strategies, as well as studies of other diverse tree families.
"This paper demonstrates that oaks have repeatedly and globally diversified in response to ecological opportunity," Andrew Hipp, lead study author and senior scientist at the Morton Arboretum in Lisle, Illinois, said in a news release. "The changes in the global landscape have given us the gift of the oak diversity we observe today."
The genomic analysis of Hipp and his colleagues at the Morton Arboretum were aided by scientists from 17 institutions around the world. Their efforts showed that there is no one region of the oak genome that houses the tree family's evolutionary history. Instead, scientists found the histories of different lineages hiding among a single gene or stretch of DNA. In fact, a small section of a tree's genome can house the evolutionary history of a single oak lineage, as well as the history of hybridization for a different lineage.
"The current study makes clear that the phylogeny we unravel will neither be unitary nor told by a small subset of the genome, as the regions of the genome capturing the divergence history for one clade are not the regions capturing the divergence history of another," researchers wrote in their paper, published this week in the journal New Phytologist.
The new analysis showed that oaks, in addition to diversifying as trees adapted to new ecosystems, continued to diversify across the same regions. Waves of diversification played out over the same areas, as new species migrated, interbred and hybridized with those that came before and and diversified once more.
"For the first time, this paper demonstrates that the history of different [oak] lineages is driven by different sets of genes," said study co-author Antoine Kremer from the French National Institute for Agricultural Research. "The story of oak evolution is especially fascinating due to the ecological and morphological convergence in different oak lineages that cohabit on the same continent."
In addition to providing food and shelter for a diversity of insects, mammals, birds and fungi, oaks have served as a vital natural resource for humans. Across human history, oak wood has been used to build ships, homes, wine barrels and furniture. And they provide more biomass than any other tree family in the world, helping to store carbon and clean the air.
Despite their tremendous service to human and ecological health, oaks are threatened in many parts of the world. Pests, disease and habitat loss are the tree family's greatest threats. The authors of the latest study hope their work will inspire communities to better protect the diversity of the oak family.