Calling Madagascar a biodiversity playground borders on a cliché. With more than 90% of plants and animals found only on this island in the Indian Ocean, this is a great place to study how geographic isolation drives evolution. Its plants and animals followed an evolutionary path 150 million years ago from the continent of Africa and 80 million years before it separated from the Indian subcontinent. The great island diversity and smaller gene pools allowed mammals to diversify more rapidly than their land relatives.
However, the island's isolation cannot protect its flora and fauna from overfishing, habitat loss, and the planet's changing climate. More than 120 of Madagascar's 219 mammal species are threatened, including 109 of its iconic lemurs. Extinction is a possibility if humans are not careful.
[Related: Giant beasts once roamed Madagascar. What happened to you?]
A study published Jan. 10 in the journal Nature Communication examined how long it took Madagascar's endangered mammals to face extinction, and estimated how long it would take for a new, equally complex group of mammal species to emerge in their native country. The answer is longer than other islands in the Caribbean: 23 million years.
"It is quite clear that there are entire lineages of unique mammals that exist only in Madagascar that are extinct or on the verge of extinction, and unless urgent action is taken, Madagascar will lose 23 million years of mammalian evolutionary history, meaning that these lineages are unique to the rest of the Earth. there will never be again,” study co-author Steve Goodman, MacArthur biologist at the Field Museum in Chicago and scientific manager of the Vahatra Society in Antananarivo, Madagascar, said in a press release.
One of Madagascar's remarkable losses to biodiversity is the faster pace of evolution, extinction, of the islands. More than 50 percent of Madagascar's mammals are on the International Union for Conservation of Nature's (IUCN) Red List of Threatened Species.
In this study, an international team of Madagascar, European and American scientists compiled a dataset of all mammal species known to have coexisted with humans on Madagascar over the past 2,500 years. They found 219 mammal species known to be alive today, including lemurs the size of a gorilla, and another 30 that have gone extinct in the last two millennia. These megafauna disappeared 500-2000 years ago.
[Related: Cave divers beneath Madagascar uncover secrets of the past.]
The team created a genetic family tree that shows how all of these species are related and how long it took for them to evolve from a common ancestor. Scientists can then determine how long it took for biodiversity to evolve and estimate how long it would take for evolution to occur if all endangered mammals went extinct.
It will take about 3 million years to restore the diversity of land mammals that have become extinct. Models show that it would take 23 million years to rebuild this diversity if all currently endangered mammals were to disappear.
"This is significantly longer than previous studies found on other islands such as New Zealand or the Caribbean," said study co-author Luis Valente, a biologist at the Naturalis Biodiversity Center and the University of Groningen in the Netherlands. statement. . Madagascar is already known as a biodiversity hotspot, but this new study puts into context how valuable this diversity is. These results open up a new evolutionary perspective on potential conservation benefits in Madagascar.
The team added that this is a turning point for the conservation of Madagascar's biodiversity, and we have about five years to advance conservation efforts on an island hampered by the political inequalities and corruption that can hinder land use decisions.
"Madagascar's biological crisis has nothing to do with biology. We are talking about a social economy," said Gudman. "We can't deny it. We have to push this thing as far as we can and try to give the impression to the world that it's now or never.
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