The loss of species that are genetically rare and geographically isolated is more damaging to the overall diversity of life on Earth over time than previously thought, according to a mathematical model described online in Ecology Letters.

Conservation needs to consider the evolutionary relationship between species said lead author of the study Hélène Morlon of the University of California at Berkeley. Preserving the most unrelated species and unique genetic types would maximize protection of biological innovations developed over millions of years.

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To build the model, the researchers traced 538 species of woody plants genetic lineage back to their common ancestor. The species all came from Mediterranean habitats in Australia, California, Chile, and South Africa. They then mathematically analyzed how evolutionary diversity increases with the size of the geographic area. The breakdown of evolutionary similarity caused by geographic separation was also calculated.

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They found that the extinction of certain plants would have a larger impact on biological diversity than previously thought, Morlon said. Plant types with limited ranges could represent unique biological innovations. But some types of plant were found in multiple regions, so the loss of one of them would not be wiping out an entire lineage.

“If you consider a branch of the tree of life that is present in the Northwest and also in South Africa, you can lose one while the other remains to preserve diversity on the planet,” Morlon said.

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The research suggests that when conservation strategies are developed, scientists and officials need to consider whether species are evolutionarily unusual. The mathematical modeling system could serve to help people decided what species need special consideration.

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By prioritizing the preservation of the widest span of evolutionary diversity possible, the biological variety of the Earth could bounce back faster from the current wave of human-caused extinctions.

PHOTO 1: A plant from the proteaceae family Banksia hookeriana growing in Australia. CREDIT: H. Morlon

PHOTO 2: These plants, commonly known as laurel protea, grow in South Africa. They are an example of related woody plants growing in geographically distant regions. CREDIT: H. Morlon