Evolutionary history a better key for conservation targets

An “extinction crisis” is affecting every continent on earth, but a new study published in the journal Proceedings of the Royal Society B has identified Australia, Central Asia, Spain and North Africa as among the most vital areas in need of protection “for conservation of the mammalian tree of life”.

Researchers led by Dan Rosauer from Australian National University have taken a new approach towards gaining the most conservation benefit from limited resources, both in terms of money and land.

Efforts that focus on preserving specific endangered species based on how many of each remain are well known and often highly visible. But the new study takes what its authors believe is a more realistic and effective global approach to conservation at the family tree level, taking into account a group’s evolutionary history — its phylogenetic diversity — and also how much territory is available to be set aside for the animals’ preservation. 

The study uses maps of about 4700 land mammals’ habitats, and genetic information on how species are related to each other, to identify important places across the world for protecting mammal diversity. It identifies key places on every continent, including parts of coastal Queensland, Australian deserts near Alice Springs, Sumatra and Java, Madagascar, India, China and Spain.

The researchers say their method is a substantially more effective solution “for conserving the diversity of mammal evolution along with minimum target areas for habitat protection”.

“This study seeks to protect all land mammals but it gives top priority to species with no close relatives, because if they were lost there would be nothing like them left,” Rosauer says. 

“This is the first time that anyone has mapped these priority areas for conserving the diversity of mammal evolution along with minimum target areas for habitat protection.”

He says that by using the most up-to-date genetic information, scientists can make superior decisions, protecting up to 32 per cent more of the diversity of the mammal tree of life through better use of limited resources.

Animals with few close relatives include the echidna and platypus in Australia, the lemur in Madagascar, the aardvark in Africa, and the mouse-like marsupial monito del monte (Dromiciops gliroides) in South America.

“The platypus and echidna separated from each other around 25 million years ago,” Rosauer says. “And they split from the rest of the early mammals way back in the time of the dinosaurs. By targeting areas with these really unique species, you would also protect a lot of other species, too.”

Rosauer says his team’s conservation solution is “substantially more effective” than one focused on species because a species-based approach ignores evolutionary relationships.

Rather than simply counting the number of animals in any given area, evaluating a conservation effort according to its genetic diversity quantifies the amount of difference represented by those animals. It takes into account factors such as ecosystem productivity and plant medicinal uses, and considers the value of protecting diversity that is not yet known to be important.

The study says the discrepancy between species-based versus genetic diversity evaluations increases rapidly as the amount of land available for conservation declines, as does the relative benefit for mammal conservation for the same area protected. “This benefit is equivalent to an additional 5900 million years of distinct mammalian evolution captured simply through a better informed choice of priority areas,” it says.

“Habitat loss is a major threat to the world’s mammal species — over 1000 mammal species are already threatened,” Rosauer says. “Scientists have often focused on the number of species in a protected area, but studies like this one consider the degree to which the family tree of life is well represented.”

The study identifies 2.7% of widely scattered global land as “highly irreplaceable for conserving the greatest possible portion of mammal diversity within the set limit of global land area, and thus critically important for ensuring the future of the world’s diverse mammal lineages.” 

High-priority areas for efficient conservation that were overlooked in species analysis but identified through genetic study were found across all continents, but particularly in parts of Australia, central Asia, Spain and North Africa. 

Most the areas identified for genetic conservation in western Russia, Australia, Madagascar, South Africa and north-west US did not match areas previously selected for species conservation. 

If more limited — or possibly more achievable — conservation options are considered, or if the pool of potential areas for conservation is smaller in the future, the choice between species and genetic-based priorities will matter greatly, and the use of phylogenetic information will be more important to protect the tree of life.

One of the study’s key aims, to which it returns again and again, is to highlight the limitations on land and funds to implement successful protection strategies. Although it identifies 12.9% of non-Antarctic global land as desirable for conservation, it says the resources and land available for the targeted “conservation of known portions of the tree of life may be far more limited than the size of existing conservation areas, or current agreements would suggest”.

It cites “strong biases” in the location of existing reserves, and notes that some areas designated for preservation based on genetic diversity “are often not managed effectively for conservation, so a clear indication of the very most irreplaceable areas under the most limited conservation scenarios may be of practical use to target improved management and identify new focuses for globally important conservation”.

“Safeguarding the tree of life is increasingly recognised as a high priority,” Rosauer says. “We conducted a first systematic global assessment of the conservation of phylogenetic diversity that uses realistic area targets and highlights the key areas for conservation of the mammalian tree of life.”

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