Posts Tagged Genetic Diversity
I was watching yet another presentation about the possibility of reviving extinct life forms (http://www.ted.com/talks/hendrik_poinar_bring_back_the_woolly_mammoth.html). Now that we appear to have the technology, at least in theory, to extract DNA from long dead animals and place it in currently extant species there seem to be more and more articles about how terrific it would be to bring them back from oblivion. This particular talk concerned reviving the woolly mammoth but I have seen similar ones suggesting restoring the thylacine, or Tasmanian tiger, to life.
Technology has been astonishingly uninspiring when it comes to saving the world’s current long list of endangered species. While there have been a few cases of successful artificial insemination or an embryo from an endangered species being reared to term by a surrogate (http://www.scientificamerican.com/article.cfm?id=cloning-endangered-animals), the majority of effective conservation programs have relied on natural breeding to create enough animals to sustain a population, along with addressing the causes why the species became endangered in the first place. There are too many unknowns when it comes to artificially breeding wild animals: how best to harvest the eggs and collect sperm, how to freeze gametes and embryos, synchronising reproductive cycles, carrying a foreign species to term, providing appropriate milk, etc, etc. All these difficulties, and more, apply to the resurrection of extinct species.
If we are able to successfully impregnate a surrogate that takes the pregnancy to term, then what? We have a single individual being reared by an individual of a different species. If this works what do we then do with our mammoth or thylacine? Apparently appropriate mammoth habitat exists in Siberia. But what would our solitary mammoth do in such a place? We would need to produce at least 50 mammoths (probably more like 500: http://www.eoearth.org/article/Minimum_viable_population_size?topic=58074), to create a self-sustaining population. Given the paucity of genetic material available to play with, these mammoths would be virtual clones with very little genetic diversity. All conservation programs seek to maximise genetic diversity to avoid the problems that now occur in inbred populations e.g. Tasmanian devils and their contagious cancer.
What would be the point of bringing back one species? The mammoth will be no more than a curio, devoid of any real value, unless you bring back its entire ecosystem. This ecosystem would need to include not just all the extinct animals but also all the plants it shared its former existence with.
There is more logic in restoring the thylacine as it only became extinct in the 1930s, not 4000 years ago, but even there the Tasmanian ecosystem has changed in the past 70 years. Would it not make more sense to invest all that time, money and expertise into preventing other species from heading down the same extinction path, instead of wasting it on frivolous projects whose only purpose seems to be to let scientists marvel at their own cleverness?
Dr. F. Bunny
Who’s that you’ve got with you, Skip?
An OBP. What’s that, an Ordinary Bloody Parrot?
Sorry, an orange bellied parrot. Handsome fellow. Why is he looking so glum?
Because there are only 36 of his friends left in the wild (http://www.theage.com.au/environment/conservation/no-flight-of-fancy-this-rare-bird-needs-to-be-caught-to-survive-20120901-257ji.html).
But there has been a captive breeding program going for nearly 20 years. Hasn’t this program been breeding birds to release back into the wild?
I see. The captive parrots have poor fertility, possibly because the founders are descended from only six birds. Why weren’t birds brought in from the wild to increase their genetic diversity?
Oh, permission to do exactly that was sought several times but wasn’t given until now. A bit like shutting the gate after the parrot has bolted, eh Skip?
But I thought they were doing okay in the wild? Weren’t there at least 150 birds as late as 2006? So what’s caused the population crash?
No one knows? But I read that there are plans to release birds into the wild this summer (which has been happening most summers for over ten years now). If we don’t know why numbers have declined so dramatically, and prior releases have failed to increase population numbers, and a lot of the captive birds are inbred then that doesn’t seem like such a great idea does it? Why are you looking at me like that?
Hold on. Who is that over there? It looks like an eastern barred bandicoot. Some of them have been released onto French Island. Unfortunately that is turning into a bit of a debacle too. While French Island is meant to be fox free it certainly isn’t feral cat free. There’s even a picture of a cat with a bandicoot in its mouth (http://bird.net.au/bird/index.php?title=Eastern_Barred_Bandicoot). Despite that bandicoots have still been released onto French Island and (surprise, surprise) they are being predated by the cats that live there (http://bird.net.au/bird/index.php?title=French_Island_Eastern_Barred_Bandicoot_Trial_Release). The New Zealanders did not start returning birds to their offshore islands until every last cat and rat had been eradicated from them. You would think the Australians would have learnt something from that. You are still looking at me strangely, Skip.
Dr. F. Bunny