Nearly one fifth of the genetic diversity of the planet’s most vulnerable species may already be lost, an analysis published today (September 22) in Science finds. If accurate, it would mean that many species are already below a conservation threshold proposed last year by the Convention on Biological Diversity (CBD) a part of the United Nations Environment Programme.

Calculating lost genetic diversity

Moisés Expósito-Alonso was in his back yard in Menlo Park, California, last year reading a monograph on the unified theory of biodiversity—“kind of a nerd thing to do,” he says—when an idea dawned on him. He kept seeing concepts related to biodiversity and realized that those concepts should also relate to the genetic diversity of a given species.

Expósito-Alonso, an evolutionary geneticist and ecologist at Stanford University, says that one equation in particular caught his eye: the species-area relationship (SAR), a function that predicts that species-level biodiversity becomes richer as habitat area expands. Essentially, it says that “when you explore ecosystems, you continuously find more species because you find more little niches to which different species have adapted,” he says. And as humans have increasingly carved up ecosystems for our own purposes, the SAR holds that the reverse is also true—shrinking habitat areas diminish species biodiversity. Researchers have used the SAR to estimate extinction rates, and it has been cited in policy-making decisions, Expósito-Alonso says; so, he began to wonder if a genetic diversity equivalent existed that could analogously predict how habitat loss reduces genetic diversity.

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