Rainforest Lizards Yield Clues to Diversity
11/23/99
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Title: Rainforest Lizards Yield Clues to Diversity
Source: Environment News Service
Status: Copyright 1999, contact source for permission to reprint
Date: November 23, 1999
SAN FRANCISCO, California- Challenging long held views that
geographic isolation is the singular driver of species diversity in
tropical rainforests, a team of researchers reports that natural
selection in forest peripheries, or "ecotones," may play an equally
important role in the evolution of new species.
Researchers from Boston University, San Francisco State University
(SFSU), and the University of Queensland in Australia reported their
findings in the Proceedings of the National Academy of Science
(PNAS).
While studying a lizard known as the common skink, which inhabits
Australia's wet tropical rainforests and dry open forests,
researchers found that despite evidence of genetic exchange, skink
populations living within the ecotone between the two forests showed
significant differences in their physical appearance compared to
their rainforest counterparts.
In striking contrast, rainforest skink populations that have been
geographically isolated by a mountain barrier for millions of years
were uniformly similar, despite ancient genetic divergence.
The team sampled adult skinks from eight paired sights in rainforest
and open forest in the Wet Tropics World Heritage area of North
Queensland, Australia.
"The differences in the shape, size, and sexual maturity of skinks
between the rainforest and adjacent open forest populations, but not
between historically-isolated populations, suggests that natural
selection rather than isolation is promoting these physical
differences," said the study's lead author Chris Schneider of Boston
University. "This stands in stark contrast to the prevailing view
that geographic isolation alone is the key to population divergence
and speciation."
Because preserving the processes that maintain diversity in
rainforests is fundamental to effective conservation, the researchers
are launching a comprehensive investigation of the mechanisms
responsible for generating biodiversity in the world's tropical
rainforests.
With a US$2.6 million grant from the National Science Foundation
(NSF), evolutionary biologist Thomas Smith will lead an international
team of scientists, students, and policy makers on a three- continent
study to test alternative hypothesis of speciation, with the goal of
defining better conservation policy. Collaborating institutions
include NASA, the World Resources Institute, Boston University, UCLA,
and the University of Queensland.
"The general belief is that if we preserve rainforests, we're also
preserving the processes that create biodiversity. But considering
the role of ecotones, that may not be the case," said Smith. His
groundbreaking work published in Science two years ago revealed that
West African ecotones are hotbeds of evolution, functioning as
engines of biodiversity in the region's tropical rainforests.
The evolutionary mechanisms that have fostered plant and animal
species found in tropical rainforests, which harbor roughly half the
Earth's species, have been hotly debated for decades.
In their new study, the researchers will test competing speciation
hypotheses across various landscapes and diverse taxa -- including
birds, mammals, reptiles, and amphibians -- in Africa, Australia, and
South America. Their goal is to identify the key factors important to
speciation in tropical rainforests.
"Ultimately, what we're trying to do with this grant is put science
and policy on the same track," says Smith. "At present, conservation
programs tend to emphasize preserving areas of high species richness,
with little attention to the evolutionary processes that generate
biodiversity. Our research model is designed to provide the data
necessary to define more effective conservation policy."