Should we hybridise endangered species?

With the ecosystems of the world up a certain creek without a proverbial paddle, and extinctions occurring faster than any time since the dinosaurs were wiped out, could we preserve some of the genetic material of endangered species by hybridising it with a close relative. In a world on fire, is that not worth a go? To talk through the pros and cons, the University of California Davis’ Andrew Whitehead.

Andrew - I think what's really cool to think about is that we, ourselves, as a species are a product of hybridisation. When modern humans migrated out of Africa, we encountered a number of other Hominid species and hybridised and interbred with them. And we can see that through the archaeological record and we can actually see it in our DNA. So it's cool to think that we ourselves are a product of hybridisation that just really emphasises that hybridisation is a natural process. Happens all the time. We as a species have also used hybridisation as agriculture. For example, domestication of various plants has involved hybridisation. For example, strawberries. Bananas are also a product of hybridisation of different cultivars. And we've also used it sparingly in conservation so far. Usually when a species is totally at the brink of extinction and is facing inbreeding depression, that's when individuals meet with close relatives and that can be really problematic genetically speaking. So probably the most well-known example is the rescue of Florida panthers by deliberately mating them with a different subspecies of panther from Texas. And that injected enough genetic variation into the Florida species so that, you know, they started doing better, at least brought them out of the death spiral of inbreeding depression.

Will - That sounds like a pretty potent argument in favour of hybridisation. Is that the only reason that we would do it, if they were in such dire straits that this was kind of the only way out?

Andrew - Our thinking about the use of hybridisation and conservation has really changed over the decades, and very, very quickly I might add. And part of that is that things are just getting more and more dire. And there are lots of really good reasons to avoid hybridisation because it can break down species barriers. And we're trying to deal with the biodiversity crisis. We're trying to maintain species. And through hybridisation we're sort of deliberately breaking those species barriers and homogenising species. And that seems to go antithetical to this idea of maintaining species diversity. But when certain important species are facing extinction, it's either no species or some blending of species is sort of the option that conservationists are faced with. And in those situations, I think over the last few decades, more of those situations have arisen and will continue to arise as species face the brink. And we're now facing these decisions about maintaining some of that genetic variation represented by that species, by blending that genetic variation with other species to at least maintain that ecosystem function. So maintaining isolated, intact original species is becoming harder and harder to do for some species. I think that should be the goal to maintain that diversity of ecosystems. But sometimes that's not possible.

Will - So to pick an example then, if there was a very fragile ecosystem that needed a large organism acting in the same way that an elephant is an ecosystem driver and that big mammal is dying out, would a hybridisation therefore be kind of useful in the way of keeping that ecosystem up and running?

Andrew - A thing to keep in mind is most ecosystems aren't a product of a single species. And usually when an ecosystem is in trouble, it's because many species are in trouble and fixing one species, trying to engineer the success of one species, is usually not going to cut it. And the problem is why is this ecosystem in decline in the first place. And it's usually because of factors that aren't going to be fixed by hybridisation. So hybridisation is in many instances a bandaid solution. It's a sideline solution. It might be important because what goes on on the sidelines, as we all know, can be important. But the main show is on the field, and that's the integrity of ecosystems. That's the integrity of the evolutionary process itself. And many argue that that's where conservation efforts should be focused, not on individual species, but on maintaining and conserving landscapes in a way that enables continuance of the evolutionary process.

Will - Yes, I suppose saving an organism or preserving as much of it as you can is all well and good, but if the place that it lives is on fire, that's not really going to help in the long run, is it?

Andrew - And it's important to recognise, if you look at the species that we work really, really hard to preserve, they're usually species that kind of look like us <laugh> that are big creatures with backbones that are cute and furry or that we like to eat. And those aren't necessarily the most ecologically important species in every instance. So we need to recognise our own bias in the species that we choose to conserve, that those efforts might be misdirected in terms of eyes on the prize of conserving ecosystems and evolutionary processes.

Will - So almost to step away from the genetics for just a second, and you've alluded to it throughout this entire thing, but rather than focusing the finite amount of time and effort that we have as conservationists on trying to hybridise individual species, what would you recommend instead for the overall health of the ecosystem?

Andrew - Part of what I think is an important part of the solution requires us to swallow our ego as a species <laugh>, and that's hard for us to do, and thinking that we are smarter than the natural sorting of genetic variation in enabling sort of long-term persistence of species. So conservation is often an intervention to preserve individual species. It's also often thought of as an intervention to preserve landscapes so that nature can take care of itself through other evolutionary processes. So to think that we can genetically engineer species in a more durable way than nature can is entirely delusional. So I think the meagre resources that we often have to deal with as a society to put towards conservation should be less towards these highly micromanaging intervention kind of things where we try to save individual species and more towards preserving landscapes and evolutionary processes so that nature can take care of itself, which is going to be much more efficient than a single species, us, thinking we know what the solution is at the genetic level.