for National Geographic News
In a study released today, researchers warn that the loss of plants and animals currently listed as threatened or endangered could have a domino effect on other species that depend on them.
The scientists estimate if the nearly 12,200 animals and plants worldwide currently listed as threatened or endangered were to disappear, another 6,300 "affiliate" species could also be lost.
"Many plants and animals have a diverse selection of insects, fungi, and other organisms associated with them that are uniquely adapted to their host," the researchers wrote in a study published in tomorrow's issue of Science.
Such specialization makes affiliate species especially vulnerable to extinction should the host species die out, the scientists say.
The researchers believe these dependent species should now be included in current extinction estimates. They add that coextinction (the loss of one species resulting from the loss of another) is a largely unexamined and potentially substantial contributor to the current global extinction crisis.
The team used a model based on known coevolved relationships between organisms such as fig trees and the fig wasps that pollinate them, and parasitic butterflies and their host ants. The analysis identified a further 6,300 endangered species.
The study also highlights at least 200 plants and animals that have already been lost through coextinction.
Co-author Navjot Sodhi says an examination of the skins of extinct animals would likely reveal many more examples of coextinct creatures.
"A parasite on the dodo could have gone coextinct if the dodo was its only host bird," said Sodhi, a biologist at the National University of Singapore.
While the plight of parasitic lice and mites are unlikely to attract outpourings of public sympathy, more charismatic insects are also at risk.
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