CONSERVATION OR CURIOSITY?Among the thrills of citizen science is the possibility of discovering a new species or, better yet, the ‘rediscovery’ of a species thought to be extinct. However, an increasingly likely prospect is that genetic technology will allow scientists to make the notion of extinction … well ... extinct, at least for some species. As resurrecting versions of extinct species becomes increasingly feasible, conservation genetics researcher Helen Taylor questions whether ‘de-extinction’ can ever become a useful conservation tool.

Imagine you’re walking through the Tasmanian bush. You hear something snuffling in the undergrowth. You pause as a creature emerges. It’s sleek and dog-like, with pointed ears

twitching and alert, but it also has a long straight tail and tiger-esque stripes on its back. It eyes you inquisitively, head cocked, gives an exceptionally wide-mouthed yawn, and trots back into the forest, disappearing between the gum trees. You’ve just encountered a thylacine – an animal declared extinct in 1936.

This may seem an unlikely meeting, but a world repopulated by thylacines, moa, mammoths and other long-lost creatures is the vision of many researchers and philanthropists behind the de-extinction movement. It’s an exciting idea that has captured people’s imaginations, but is it feasible? If so, is it really the futuristic conservation strategy its supporters claim we need?

We’re closer than you thinkIn 2009, a mountain goat kid was born via caesarean section at a captive-breeding facility in Spain. It struggled to breathe and died from a lung defect within ten minutes of being delivered – sad, but not unusual in a breeding program. This was no ordinary mountain goat; the kid was a clone of the last known Pyrenean ibex, or bucardo – a subspecies of Spanish ibex that went extinct nine years earlier. Scientists used skin cells taken from Celia, the last known living bucardo, to grow clonal embryos, which they implanted into 57 Spanish ibex and Spanish ibex goat hybrid surrogate mothers. Only one of the resulting seven pregnancies went to term, culminating in the tragically short life of the only animal to be brought back from extinction so far.

The Franco-Spanish team behind bringing back the bucardo are not the only researchers striving towards de-extinction. At the University of New South Wales, Professor Mike Archer’s Project

Lazarus team has produced very early stage embryos of the gastric-brooding frog, a remarkable amphibian that could turn its stomach into a womb until the species went extinct in 1983.

In America, de-extinction devotee Professor George Church believes he is two years away from creating an elephant embryo that contains woolly mammoth DNA. The bucardo did not survive, the frog embryos die a few days into development, and an Asian elephant with a few mammoth genes is definitely not a mammoth, but these are still significant steps towards reviving species that we once thought were gone for good.

No facsimile Even if de-extinction projects prove successful, they won’t create exact copies of the species we have lost. Current pathways to de-extinction introduce genetic information from species closely related to the target animal into the resurrected species. The end result looks similar, but it’s not an exact genetic copy.

The first option is to try to get back to your de-extinction target by ‘back breeding’ existing species, aiming to create an animal that looks like the extinct species by choosing individuals with similar characteristics. Alternatively, you could take the route trialled with the bucardo and the gastric-brooding frog. Take a cell from a closely related species, clear out its nuclear DNA, fill it with DNA from the extinct species, grow an embryo in a test tube and implant it in the womb/egg of the closely related species. The new DNA can come from two sources: ancient, fragmented DNA from permafrost or museum specimens, with the gaps in the genetic code filled in with DNA from a closely related species, or from a fully intact genome sequenced from some kind of tissue sample preserved before the species went extinct. Even when you don’t need to fill in gaps in the genomes, the cell from the closely related species

CONSERVATION INNOVATION

Image: Joseph Wolf

De-extinction:

40 | Wildlife Australia | SPRING 2017

will contain mitochondrial DNA from that host species. This mitochondrial DNA will end up being present in every cell of the new organism, and it’s still up for debate how important that type of DNA is in speciation. So, the new creature might look a bit (or even a lot) like its extinct predecessor, but it is not a genetic facsimile, and it may not behave in the same way.

For extinct mammals, cloning methods require embryos to be grown in the womb of a closely related species. For a thylacine, for example, this could be a Tasmanian devil, but it introduces environmental differences even before birth that could have important epigenetic consequences, changing the way genes are expressed. Fostering by a closely related species will likely result in an absence of at least some behaviours that would have been natural prior to extinction. So, we could make a mammoth-like elephant but not a mammoth. We can’t resurrect species, but we can probably create proxies similar to the extinct species. Extinction really is forever, but these proxies could still play an important role in restoring ecosystems.

The case for de-extinctionUnderstandably, de-extinction comes with ethical concerns. Many worry about the animal rights issues for the resurrected species and their surrogate mothers, and scientists ‘playing God’. Some also suggest we will care less about conserving species if we believe extinction is not forever and we can simply ‘de-extinct’ species later on. Others raise the issue of a handful of resurrected individuals in zoos or labs, marvelled at as curiosities but with no hope of a return to the wild: essentially, scientific circus freaks.

Conversely, many de-extinction fans feel we have a moral obligation to restore species that humans drove to extinction. They argue that resurrected proxies could play an important conservation role. When a species goes extinct, it leaves a hole in an ecosystem. If another species does not move into the vacant niche, then that job no longer gets done. The loss of moa from New Zealand likely altered the composition of forests because moa were such important browsers. Could bringing back moa help restore New Zealand’s forests? An overriding motivation for many de-extinction fans is, understandably, excitement around the possibilities and the technological advances; it’s very sexy science. But to move from cool to conservation, de-extinction needs to overcome numerous hurdles.

Ecosystem re-integrationThe ecosystems for many de-extinction candidates have experienced numerous changes in the time since extinction. If the habitat the species used to live in no longer exists, should we even consider bringing that species back? New Zealand now plays host to over 2400 naturalised exotic plant species – it’s impossible

to predict how a moa proxy would interact with them and whether the outcomes would be positive or negative. A species’ contribution to its ecosystem also doesn’t stop with what it eats.

Every individual animal carries its own communities of microbiota – bacteria, fungi, and microbes – as well as parasites, all of which are important players in the health of the individual and the ecosystem it inhabits. Many of these tiny organisms disappeared with their extinct hosts. If we bring back proxies, should we also bring back proxies of their internal fauna? It’s a tough ask given that we often don’t know the exact composition of these internal ecosystems. Resurrected proxies might resemble their extinct counterparts biologically, but resurrecting their ecology is perhaps even more challenging.

Importantly, we don’t necessarily need to bring back extinct species to fill functional gaps in ecosystems. If a species has been lost in one area but still exists in another, once the reasons for extinction have been removed, the species could be reintroduced. Tasmanian devils don’t have to be confined to Tasmania – they could rip apart carcasses all across their historical Australian range, given half a chance. Alternatively, if a species with an important ecosystem function is totally extinct, but another species could fulfil the role, that species could be introduced. This has already been trialled, introducing a tortoise from the Seychelles to resume the grazing and seed dispersal functions of the extinct giant tortoise of Mauritius, and is planned for more tortoise species in Madagascar and the Galapagos.

Avoiding a genetic bottleneckSmall initial starting populations could also quickly turn de-extinction into re-extinction. In conservation management, we generally try to avoid populations becoming too small, as that leads to reduced genetic diversity, inhibiting a species’ ability to adapt to changing circumstances. The chance of inbreeding also increases, which can cause issues with reproduction and survival, keeping the population small and leading to an almost inescapable extinction vortex. If the resurrected proxies are to become functional, self-sustaining populations, they will need to overcome this issue.

It’s also highly unlikely that we would know how much genetic diversity originally existed in the population before it went extinct. We might have genetic material from museum collections and/or fossils, which will give us some idea what variants of each gene previously existed in the species, but it is unlikely to be the whole story. So we might be able to genetically engineer some of the historical genetic diversity back into the resurrected proxy, but not all of it. Our resurrected proxy will potentially be more vulnerable to disease events and climate change than its extinct predecessor – not the strongest start.

The first extinct species to be ‘resurrected’, and the only one at the time of writing, was the Pyrenean Ibex, although the kid died shortly after birth. Image: Joseph Wolf

Consideration must be given to how restoring species affects their former ecosystem. If moa were brought back, would we have to restore Haast’s eagle, which preyed on moa but is now also extinct? Image: John Megahan [CC]

Wildlife Australia | 41

Diverting funds from endangered speciesConservation funding is already stretched, and there are concerns that de-extinction could divert money away from conserving real live endangered species. Whether or not this is true largely depends on where the money for de-extinction comes from. If resurrection projects are funded by private, philanthropic donors, it can be argued that the money may never have gone to conservation otherwise. If, however, research funding is diverted away from conservation projects and towards de-extinction, then de-extinction could be to the detriment of existing conservation efforts. Increasingly, researchers and conservationists are using crowd-funding to underwrite their projects. In this arena, de-extinction competes with conservation, as both teams arguably target the same audience. It is also possible that some of the techniques being investigated for de-extinction could help conserve endangered species. Gene editing could be used to reintroduce lost genetic variation from museum specimens into surviving populations with low genetic diversity. In this way, de-extinction could benefit conservation, although perhaps not quite in the way its proponents envisage.

Carefully prioritising which species should be resurrected is also important. The most realistic and potentially useful candidates for de-extinction would be species that were only recently lost from the landscape. On that score, the gastric-brooding frog, the bucardo, and possibly the thylacine are decent targets, but mammoth and moa are not. Unfortunately, many de-extinction target species seem to have been selected based on charisma rather than conservation outcomes, casting doubt on the conservation motivations of many de-extinction projects.

Efforts to engineer functional proxies of extinct species are gathering momentum, and excitement is understandably high. The techniques that emerge from de-extinction research may or may not prove useful for conserving threatened species, but they won’t bring back exact replicas of extinct creatures. While you or your children may one day see a thylacine-like creature padding through the bush, it won’t be a thylacine (not unless the species is ‘rediscovered’ rather than ‘resurrected’). More importantly, the challenges of producing a proxy are only the beginning. Releasing these creations into the wild is fraught with problems that are only just starting to be considered. Interestingly, the people considering the post-release challenges for resurrected species tend to be conservation scientists rather than de-extinction researchers. Those pushing for de-extinction may claim there are biodiversity benefits, but so far, de-extinction seems driven by curiosity rather than conservation concern.

READING Steeves TE, Johnson JA, Hale ML. Maximising evolutionary potential in functional proxies for extinct species: a conservation genetic perspective on de-extinction. Functional Ecology 31.5: 1032–1040. Bennett JR, et al. 2017. Spending limited resources on de-extinction could lead to net biodiversity loss. Nature Ecology & Evolution, 1, p.0053. Berns GS, Ashwell KW. 2017. Reconstruction of the cortical maps of the Tasmanian tiger and comparison to the Tasmanian devil. PloS one, 12(1): p.e0168993 Seddon PJ, 2017. The ecology of de-extinction. Functional Ecology, 31(5): 992–995. Iacona G, et al. 2016. Prioritizing revived species: what are the conservation management implications of de-extinction? Functional Ecology.

HELEN TAYLOR is a Marsden-funded research fellow at the University of Otago in Dunedin, New Zealand. She is a conservation geneticist who investigates what happens to populations when they get very small. Helen mainly works with threatened birds and is currently investigating whether inbreeding is causing poor male fertility in New Zealand’s birds.

CONSERVATION INNOVATION

I S THE THYLACINE EVEN EXTINCT?

The thylacine was declared extinct decades ago, yet 6–10 sightings (some more credible than others) are still reported annually. In 2016, Sleightholme and Campbell analysed 1167 confirmed and geo-referenced

reports from 1900–1940 of captured, killed or sighted thylacines and determined that they likely survived in the Tasmanian wilderness until the mid-1940s. A 2017 study by Carlson, Bond and Burgio used mathematical extinction theories to determine that the species could not have lasted beyond the 1960s. Despite the unlikelihood of the thylacine’s continued existence, millions of dollars have been plunged into searches. In 2016, The Bulletin offered an $AUD1.25 million prize to anyone who could prove the thylacine still lived; the money went unclaimed. More recently, a historical sighting on Cape York has prompted an extensive

camera study. Recounting his 1983 sighting to media and researchers, tour guide operator Brian Hobbs elaborated on the characteristic red eyeshine of the creature in the dark. When a respected park ranger also revealed a nocturnal sighting in the area in the 1980s, it captured the interest of Dr Sandra Abell and Professor Bill Laurance from James Cook University. Fifty camera traps, baited with a known attractant and set several kilometres apart on Cape York, will be carefully monitored for any sign of the animal until November 2017. If the thylacine lurks in northern forests, it will join a short but celebrated list of animals that have returned from extinction, including the Javan elephant, New Zealand takahe, mountain pygmy-possum (see p. 19) and the New Guinea highland wild dog (see p. 49).

Carlson CJ, Bond AL, Burgio KR. 2017. Estimating the extinction date of the thylacine accounting for unconfirmed sightings. bioRxiv, p.123331. Sleightholme SR, Campbell CR. 2016. A retrospective assessment of 20th century thylacine populations. Australian Zoologist, 38(1):102–129.

Professor Mike Archer’s Lazarus Project aims to resurrect the gastric-brooding frog. Photo: Hal Cogger

Could the Tasmanian devil prove a suitable surrogate for a thylacine proxy? A 2017 study by Gregory Burns and Ken Ashwell, who reconstructed and compared white matter tracts in the brains of Tasmanian devils and thylacines, revealed differences in the cortex, possibly because predatory thylacines need better planning and decision-making abilities than scavenging Tasmanian devils; such differences would need to be considered if de-extinction with a surrogate were to go ahead. Photo: Matthias Appel

42 | Wildlife Australia | SPRING 2017