The researchers also identified the order of evolutionary events. Most often woody plants became herbs or developed skinnier water-conducting pipes before moving into freezing climates. In contrast, plants usually began dropping their leaves after moving into freezing climates.
Identifying these evolutionary adaptations and likely paths to them, required the team to build two robust sets of data. First, researchers created a database of 49,064 species, detailing whether each species maintains a stem above ground over time, whether it loses or keeps its leaves and the width of its water-carrying pathways. To these they added whether it is ever exposed to freezing, using resources from the Global Biodiversity Information Facility and a global climate database. Then, researchers took that information and combined it with an unprecedented dated evolutionary tree with 32,223 species of plants, allowing them to model the evolution of species' traits and climate surroundings. This "timetree," which can be viewed at OneZoom here, is the most comprehensive view yet into the evolutionary history of flowering plants.
"Until now, we haven't had a compelling narrative about how leaf and stem traits have evolved to tolerate cold temperatures," Zanne said. "Our research gives us this insight, showing us the whens, hows and whys behind plant species' trait evolution and movements around the globe."
To build on these findings, researchers will use the massive tree to explore other aspects of the evolutionary history of plants, especially to examine how plants respond to additional environmental pressures besides just freezing.
Researchers will use information from the findings in countless other ways as well, Reich says.
|Contact: Patty Mattern|
University of Minnesota