As endangered species face increasing threat from changing environmental pressures, Emily Longworth examines cloning as a viable resort for species conservation
Conservation of species has been an international issue for centuries, and it is one of the key roles of our modern-day zoos and botanic gardens. Storing living collections of plant species and creating seed banks across continents has been practised for as long as biologists had means to transport their specimens. However, recent advances in genetic and molecular biology have founded a whole new type of conservation: cloning.
In the last few weeks, Embrapa, an agricultural research agency in Brazil, announced their plans to begin cloning eight species that are on the International Union for Conservation of Nature (IUCN) list of endangered species. In particular, it aims to clone the maned wolf, native to South America, in the next month. The maned wolf (Chrysocyon brachyurus) has been classed as “near threatened” by IUCN.
Only 13,000 maned wolves remain in the entirety of South America. Disease and habitat distruption have been the biggest threat to the welfare of the maned wolf, whose population has remained steadily in decline for years. Very often, they are killed as pests, not unlike foxes are, as they are inclined to kill chickens on farmlands.
The initiative to clone them has its priorities set on increasing numbers of captive specimens, as opposed to repopulating natural habitats. This is because they feel that the cloned animals may be very vulnerable if released into wild habitats. The cloned species will be maintained in captivity as a way of a ‘reserve’, in case wild populations should collapse or experience more severe decline in the future.
The seven other species that have been listed for protection are black lion tamarins, bush dogs, coatis, collared anteaters, gray brocket deer and bison, which are also listed as endangered by the IUCN. Already, 420 wild tissue samples have been taken from maned wolves in Brazil.
This is not the first time that rare or endangered species have been cloned. The European mouflon, a small wild sheep, was viably cloned in 2001. Having been classified as endangered in its original habitat, the mouflon clone survived for seven months. This made it the first clone that survived past infancy. Previously, attempts were made to clone the Pyrenean ibex, although this clone died merely 48 hours after its birth in 2000.
The cloning of the mouflon sheep was modelled on the same technology that was used to clone Dolly the sheep in 1997. This is comprised of somatic cell nuclear transfer (SCNT), which is also often referred to as “therapeutic cloning”. It works by retaining the nucleus of a somatic cell from the cloning subject, which is then fused with an egg cell from a host animal. A surrogate mother then carries the embryo until birth.
One of the key differences in cloning of the European Moufflon after Dolly was that a different sheep species was used as the surrogate mother. This made the cloning process more of an apparent success, but another factor that contributed to the success of the sheep was the extent that researchers know about their life cycles.
“We know a lot about the reproductive cycles of cattle and sheep that we don’t know for species like the black rhino and the Sumatran tiger, which makes exotic species more difficult to clone,” says Oliver Ryder, of the Centre for Reproduction of Endangered Species in the San Diego Zoo, California.
This may impact negatively for the efforts to conserve the South American species such as the maned wolf. But in cases where efforts to preserve habitat are not effective enough, cloning may be a last resort.
Betsy Dresser, director of the Audubon Center for Research of Endangered Species, in New Orleans, says that: “Any tool for saving endangered species is important, cloning is just another reproductive tool, like in-vitro fertilisation.”
There are still many problems that face the long-term viability of cloning, however. In the case of the Pyrenean Ibex, there was only one female left in existence at the time of cloning, named Celia. This means that even if it were possible to successfully clone the last remaining female, there would have been no male species available to breed with the clone.
For a population of an extinct animal to be re-established, several requirements need to be met. Primarily, a range of genetic material from the natural population is required to create genetic diversity amongst a cloned population. Without genetic diversity, the gene pool of the species is severely narrowed, and their potential to survive is hugely mitigated.
In this way, there never would have been chance for Celia, the last ibex. But with this knowledge of what is necessary for the establishment of a new population done entirely with cloning, it is possible that researchers may succeed in repopulating the maned wolf and other South American species in captivity.
“The key is foresight, to just save a little piece of skin, blood or other living cells before the genes from these individuals are lost from the planet forever,” says Robert Lanza of Advanced Cell Technology in Marlborough, Massachusetts.
With the viability of cloning becoming a reality, there are chances that cloned animals can save species lines in the course of the next century. Cloned species will be allowed to repopulate wild habitats if the natural populations are threatened to near extinction, which will potential enable us to never repeat the mistake of the dodo loss.