America bottleneck cheetah dating genetic
Maybe they’ve found a way to co-exist without interacting much,” suggests Dr. But are the meetings and matings of brown and polar bears new? POSSIBLE EFFECTS OF CLIMATE CHANGE “Clearly the polar bear lineage has experienced many warming and cooling periods.
But these natural oscillations are different today because they still occur, but over a higher and continually increasing baseline due to the accumulation of greenhouse gases.
The situation is a little like Europeans unleashing smallpox on immunologically naive Native American populations.
The diminishing genetic diversity seen among polar bears could be a danger sign.
In contrast, cheetahs are famously genetically uniform.
Their numbers plummeted through a population bottleneck about 10,000 years ago, as the most recent ice age ended, and since then natural selection has maintained a set of genes well-adapted to their environment, which hasn’t changed that much since our ancestors stopped killing them .
In contrast, positive selection reflects gene variants that give an individual a reproductive advantage.
(Darwinian “fitness” refers to reproduction or a trait that fosters successful reproduction – not being physically fit.) Genomes bear signs of positive selection for traits that give a species an advantage: a variant of a gene that is present among many if not all members of one species, but is not in closely related species.
But what happens if their habitat changes, as it seems to be doing now?Yet the telltale sequences of A, T, C and G also reveal that the two types of bears meet up once in awhile, to dine on beached blubber, and, rarely, to mate.Brown bears sharing whale blubber and sperm with female polar bears gave rise to the so-called “ABC” bears, for the Admiralty, Baranof, and Chichagof islands of the Alexander Archipelago off the coast of southeastern Alaska, their home today.So even if polar bears have experienced climate change in the past, it’s getting warmer and they are going to lose more habitat, and if it continues we can only imagine we’re going to lose polar bear populations.But what, exactly, will happen is hard to predict,” Dr. Another danger of climate change altering habitats is that polar bears may encounter animals that carry pathogens to which the displaced arctic residents aren’t immune.