The tropics are the source of a majority of the planet's biodiversity, according to a new study, underscoring the need to preserve tropical forests, reefs and other ecosystems around the world.
In a paper appearing in the Oct. 6 issue of Science, paleontologists from the University of California, Berkeley, UC San Diego and the University of Chicago show that for one large group of marine animals - oysters, clams, scallops and other bivalve mollusks - about three-quarters of today's genera originated in the tropics and spread outward toward the poles, while only one-quarter originated at higher latitudes.
Other plants and animals probably have an overwhelmingly tropical origin also, said coauthor James Valentine, professor emeritus of integrative biology at UC Berkeley.
The finding partially answers a question that has puzzled biologists for more than 100 years: Why is there a greater diversity of life in the tropics - both in the oceans and on land - than at higher latitudes?
"These species are spilling out of the tropics and increasing the diversity in temperate and arctic regions," he said. "We should preserve the tropics, because without them, there is no source anymore for diversity in higher latitudes."
"The tropics are the engine for global biodiversity," added coauthor Kaustuv Roy, associate professor of biology at UC San Diego. "What this means is that human-caused extinctions in the tropics will eventually start to affect the biological diversity in the temperate and high latitudes. This is not going to be apparent in the next 50 years, but it will be a long-term consequence."
Valentine and Roy coauthored the paper with David Jablonski, professor of geophysical sciences at the University of Chicago.
The so-called "latitudinal diversity gradient" first became obvious as early naturalists and explorers returned from expeditions with more and more new species. Today, scientists estimate that the
Contact: Robert Sanders
University of California - Berkeley