Genetic diversity within many species is declining globally, according to a recently published study.
“Any threat that reduces the size of a population, or which causes a larger population to become fragmented into two or more smaller populations, can cause a loss of genetic diversity,” lead researcher Catherine Grueber, from the Conservation Genetics Specialist Group at the IUCN, the global wildlife conservation authority, told Mongabay by email. “This is because decreasing a population’s size causes its gene pool to shrink too.”
Genetic diversity allows species to adapt to crises like disease, climate change and hunting, so a shrinking gene pool can make them less resilient.
To find out how the gene pools of various species were faring, Grueber and her colleagues looked at 882 papers published between 1985 and 2019 that analyzed genetic changes in specific animals, plants and fungi. In all, they gathered trends in genetic diversity for 628 species, some with multiple populations analyzed.
The study found that genetic diversity was declining in two-thirds of the analyzed animal and plant populations. These include populations of range-restricted species like the Arctic fox (Vulpes lagopus) and more widespread ones like the black-tailed prairie dog (Cynomys ludovicianus).
The description of the decline in terms of populations, not species, “is particularly relevant for widespread species, because even though a species may be found in many places, some of its populations may be declining or even lost. Losing those populations risks losing important genetic diversity for the species overall,” said Grueber, who is an associate professor at the University of Sydney.
Different species were affected by different kinds of threats, mostly the direct or indirect result of human activities. For example, birds were more impacted by land-use change, and fish by harvesting, the study found.
One-fifth of the species analyzed are listed as threatened on the IUCN Red List, while the rest aren’t considered threatened or lack data to determine their conservation status.
While the decline in genetic diversity is concerning, some of the studies analyzed described conservation actions that could slow or reverse genetic loss “by improving habitat quality, by restoring habitat, by establishing new populations, or by moving individuals among populations, among many others,” Grueber said.
“Because genetic diversity loss is common in small populations, even actions that maintain diversity can be a good outcome,” she added.
One example is the golden bandicoot (Isoodon auratus) in Western Australia, “for which new populations were established without loss of genetic diversity, which improves the outlook for the species,” Grueber said.
Similarly, plague caused by a certain flea can devastate black-tailed prairie dog populations. But conservationists have found that dusting their burrows with an insecticide to control the fleas helps those populations maintain higher genetic diversity than the ones not receiving the treatment. The genetic diversity of Arctic fox populations has likewise remained stable or even improved following conservation actions like the wild release of individuals from captive-breeding programs.
Banner image of a black-tailed prairie dog by Rhett A. Butler/Mongabay.