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China's Hengduan Mountains host some of the oldest flower lineages

China's Hengduan Mountains host some of the oldest flower lineages
The Hengduan Mountains are home to more than 3,000 plant species. Photo by Rick Ree/Field Museum

July 30 (UPI) -- Alpine flora found on China's Hengduan Mountains, near the Tibetan Plateau, has been evolving for longer than alpine flora found anywhere else on Earth, according to a new survey of biodiversity in the region.

The Hengduan Mountains, located in southwest China, began forming roughly 30 million years ago. New research, published Thursday in the journal Science, suggests unique groups of flowers have been growing and evolving there ever since. Today, the mountain slopes are home to more than 3,000 species.

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For the study, researchers at the Chinese Academy of Sciences and the Field Museum in Chicago used fossil and genetic analysis to piece together the evolutionary relationships among plants in the region going back tens of thousands of years.

By analyzing the genomes of the region's plants, scientists were able to tease out the relationships among them. Fossils helped researchers link plant families to the geologic timeline, revealing how long different plant lineages have been growing and evolving in the same place.

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The data not only revealed the region's flora to be especially ancient and varied, but also offered scientists fresh insights into the conditions that support the development of rich biodiversity.

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Using the results of their phylogenetic analysis, researchers constructed a model to simulate the development of biodiversity in the region.

"We used the model to simulate many thousands of possible biogeoraphic histories, and from the simulations that were consistent with the data, we drew inferences about how the alpine flora of the Hengduan Mountains was likely assembled," study co-author Richard Ree, curator of flowering plants at the Field Museum, told UPI.

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Both the model's simulations and phylogenetic data showed a combination of mountain building and monsoon-fueled erosion created conditions friendly to biodiversity.

"The conventional wisdom is that stability over many millions of years -- like in the tropics -- leads to more species, because new species are less likely to go extinct and more likely to adapt to a unique niche in the ecosystem," Ree said. "But as niches fill up, the rate of new species accumulation should go down."

The Hengduan Mountains are highly dynamic, not a pinnacle of stability. That dynamism was key to development of the region's biodiversity. Researchers were able to show relationships between geologic and meteorologic shifts and changes in speciation rates.

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Periods of uplifts across the mountain range, roughly 17 to 19 million years, corresponded with increases in biodiversity. According to their analysis, an intensification of the region's monsoon also triggered an increase in plant diversity.

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Generally speaking, mountains should have more niches than lowlands, due to different environmental conditions at different altitudes and on different slope faces," Ree said.

The ruggedness of a landscape, the research suggests, enhances local adaptation and speciation. Water also proved a boon to biodiversity.

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"The monsoons deliver moisture, which increases the carrying capacity -- the number of available niches -- for plants, but also caused extensive erosion, making valleys deeper and increasing the ruggedness of the landscape," Ree said.

Researchers suggest their work can provide context for the effects of climate change on biodiversity and evolution.

"[Our study] provides contextual knowledge about how shorter-term ecological processes related to climate change can play out over evolutionary timescales," Ree said.

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