Genetic relationships between flowering plant species (angiosperms) can be ordered on a tree-of-life, with the evolutionary history (EH) of a species represented by its position on the tree and the length of the branches. New branches arise when species diverge. The tree is not symmetrical and some families contain more species than others. When extinction occurs randomly, more EH will be preserved because most families are species-rich. With non-random extinction, however, families containing small numbers of species are at greater risk of disappearing and more EH is potentially lost.
Using the IUCN Red List of Threatened Species1 to identify Vulnerable, Endangered and Critically Endangered flowering plant species, researchers ran trials to compare the impact of random extinction with non-random extinction over a 100-year time span. In addition, the study measured originality (OG) or how irreplaceable a contribution a family makes to evolutionary history. Researchers suggest that species in families with higher originality should receive high priority status as Evolutionary Distinct Globally Threatened (EDGE)2 species.
It was found that if extinction patterns are random, the risk of entire families becoming extinct is relatively low over the next 100 years. When extinction is not by chance, but concentrated in species-poor families, there is a significant risk of entire families being lost. The study found that of the 52 families at risk, all species are at risk in over half. This compares with only 4 families at risk under random extinction scenarios.
Researchers do not believe that all threatened species will become extinct, although some unlisted species might be lost before they are listed. Instead, they estimate that within the next 100 years about one third of the species at risk will actually be lost.
This research suggests that with limited resources available for conservation, efforts should focus on families with a small number of species. More research is needed to understand the loss of the unique traits of flowering plant species and their influence on the functioning of ecosystems.