Researchers at Purdue University have recently published an article in the journal Biological Conservation, suggesting that genetics should play a stronger role in determining whether species are threatened with extinction. In the article, “The reduction of genetic diversity in threatened vertebrates and new recommendations regarding IUCN conservation rankings,” the authors argue that biologists need to identify ‘species of conservation need’ by estimating the expected loss of genetic diversity, stating that genetic diversity is necessary for allowing species to respond to changing environmental conditions.
Current criteria used by the IUCN (International Union for Conservation of Nature) for determining if a population is threatened or endangered include evidence of population decline, the range and occupancy of the population, and the estimated number of mature adults; but do not include genetic criteria. A dramatic decline in numbers tells wildlife managers that measures need to be taken to conserve the species, while increases can indicate that the population is recovering. Similarly, evidence of restricted or reduced species range, or declines in the breeding population of adults are used as indicators that a species is heading toward eventual extinction.
The study’s authors searched scientific literature to conduct a systematic, quantitative review of genetic species data published since 1990. They analyzed the data in the context of conservation by looking at how much genetic diversity exists between threatened and non-threatened species. They found that genetic diversity is reduced in threatened species, which suggests that inbreeding and naturally occurring random chance are reducing genetic diversity in endangered populations. As a species goes into decline, some populations are cut off from others, and when breeding does not occur between them, there is no gene flow, which leads to less genetic diversity over time. Additionally, the authors considered the criteria typically used to rank threats to species and found that the existing criteria fail to systematically identify populations with low genetic diversity. The current ways of identifying threatened species do not always do a good job of identifying the species with the highest risk of loss of genetic diversity.
In many places DNA is being used as way to estimate the population size of certain species. Advances in technology have made collection and storage of DNA less obtrusive and more cost effective. DNA has even been successfully extracted from the footprints of polar bears in snow, allowing researchers to identify individual polar bears without ever having to capture them. Hunters are increasingly being asked to submit a sample from their harvested animal for genetic analysis, and for some critically endangered species genetic samples from all known individuals are being stored for perpetuity. The library of genetic knowledge is continually growing.
While genetic diversity should not be the primary criteria for IUCN ranking, it seems reasonable to include it as an additional criteria for conservation ranking, especially in light of advances that make collection and analysis of DNA much more cost effective. Information obtained from better understanding genetic diversity could be the key to conserving endangered species.