Desert bighorn sheep, which live in an untouched area, are better prepared for climate change than their relatives from other regions. This primarily concerns populations from Death Valley and Grand Canyon National Parks: they are more diverse from a genetic point of view. This is the conclusion a team of researchers came to after analyzing DNA samples from more than 1,600 individuals. As the authors note in an article for the journal Frontiers in Ecology and Evolution, their work will help to better protect bighorn sheep in a changing climate.
Global climate change is already affecting animals around the world. For example, yellow-bellied marmots that live in the mountains of western North America now survive better in summer, but worse in winter. And polar bears have to starve longer due to the lack of ice.
In the future, this process will only intensify, and in order to preserve biological diversity in a changing climate, scientists are trying to understand which species and populations are most vulnerable to change. A team of researchers led by Tyler G. Creech from the University of Oregon set out to find out how climate change over the next thirty years will affect the desert bighorn sheep (Ovis canadensis nelsoni). These ungulates live in the southwestern United States and northwestern Mexico, where it is already hot and dry. In the coming decades, the climate here will become even more severe, which makes zoologists worry about the well-being of the subspecies.
Creech and his colleagues extracted genetic information from the droppings of Desert Bighorns found in the states of Arizona, California, Nevada and Utah. Some of the populations studied live in ten sites that are managed by the US National Park Service, and some in unprotected areas in their neighborhood. The researchers were interested in how genetically diverse and isolated individual groups are.
The authors analyzed the genomes of 1,652 individuals from 62 populations and compared the data obtained with geographic and climatic factors. As a result, they concluded that different groups of bighorn sheep are quite different from each other in terms of genetic diversity and vulnerability to climate change. For example, populations in the south of the range, where the climate changes the fastest, turned out to be the most isolated and least genetically diverse. In addition, they live in low mountains and hills, and they don't have much room to shift their ranges upslope as temperatures rise. The most uncertain is the fate of sheep from the southern Mojave Desert and southeastern Utah.
In contrast, bighorn sheep from the northern parts of the range have higher genetic diversity and population connectivity, and local mountains make it possible to shift ranges upward for some time. The least vulnerable to climate change turned out to be populations that live in protected areas, little affected by human activities - for example, in the national parks Death Valley and Grand Canyon. They can become the key to the survival of the subspecies in the future.
The study of another subspecies of bighorn sheep has led scientists to ambiguous conclusions. They found that females who have more babies at an early age live longer on average. However, in maturity, such individuals reproduce worse, especially if there are more males among their offspring. Sons are likely to take over more resources than daughters, taking them away from potential younger siblings.