Genomic tools for species discovery inflate estimates of species numbers, biologists contend

Date: January 31, 2017

Source: University of Michigan

Increasingly popular techniques that infer species boundaries in animals and plants solely by analyzing genetic differences are flawed and can lead to inflated diversity estimates, according to a new study from two University of Michigan evolutionary biologists.

Lacey Knowles and Jeet Sukumaran investigated the accuracy of inferences made by a mathematical model widely used to quickly determine the boundaries between species without the time-consuming, painstaking process of comparing specimens in museum collections.

They found that the genetic approach, formally known as the multispecies coalescent model, can lead to species estimates that are five to 13 times higher than the true numbers.

Because the species is the fundamental unit for all evolutionary and ecological studies, their findings are expected to have wide-ranging implications, from biodiversity studies to conservation planning. Their results are scheduled for online publication Jan. 30 in Proceedings of the National Academy of Sciences.

"This is an area that has really taken off over the last decade. On its surface, the genomic approach looks like a panacea because it's very fast and doesn't require any kind of taxonomic expertise," said Knowles, a professor in the U-M Department of Ecology and Evolutionary Biology and curator of insects at the university's Museum of Zoology.

"So it's been promoted as a way to speed up inventories of biodiversity by combining the automation of genomics with the statistical power of these models. The only problem is, this method is not doing what we think it is doing, resulting in an overestimate of species numbers."

The U-M researchers say their paper serves as both a warning and a call to action -- a warning against reliance on genomic data alone and a call for new methods to improve genomic-based species delimitation approaches.

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