We've talked before on ScienceBlogs about the extinction risk to Tasmanian Devils because of contagious cancer. Well, perhaps there's a light at the end of this population tunnel, Hope over Tasmanian Devil cancer:
The world's largest marsupial carnivore is facing extinction from a mystery facial cancer.
But scientists say Cedric appears to be naturally resistant to the contagious tumours which have killed half the devil population in Tasmania.
Cedric is the first Tasmanian Devil to have shown any immunity from the disfiguring disease.
I'll be entirely honest here: I'm not surprised. I just had a hard time believing that a species with a conservative census size of 20,000 didn't have enough extant genetic variation potentiality to come up with an evolutionary response. I've talked about the decimation of Native Americans due to disease, but even in this extreme case residual populations remained. A great deal of Native genetic material was also passed on to mestizo populations.
The power of disease and epidemics is perhaps the salient fact of existence for large organisms. It is one of the major likely reasons that complex eukaryotes tend to be sexual; asexual lineages just go extinct due to plagues. If the Tasmanian Devils were asexual Cedric would likely not exist; but as it is there is enough genetic variation that a resistant individual's immune profile will spread throughout the population and beat back the epidemic. Because of other exogenous factors conservation scientists will probably not be taking any risk (i.e., vaccines?), but nature is sometimes our best friend as well as an enemy.
Yes, of course this could be premature (read the story). But if not Cedric, nature will likely come up with another response. Biology is the science of exceptions, but we shouldn't get too fixated on the short-terms phenomena to forget the long-term dynamics. In the case of humans there are strong ethical reasons to care about short-term phenomena (i.e., selection on Native American populations today due to disease), but when it comes to animals we can give selection a freer hand.
Yay for Cedric! And hopefully others like him.
The world's largest marsupial carnivore
The world's largest remaining marsupial carnivore.