New Biodiversity Theory Suggests Rain Forest Conservation Falls Short: Saving "Edge" Habitats May Be Key To Saving Rain Forest Biodiversity

June 19, 1997

In the June 20 issue of Science, a San Francisco State University researcher reports findings that challenge long-held views on how rain forest biodiversity is generated, and suggests the key to conservation may lie in protecting overlooked transitional zones along the forest periphery.

San Francisco, June 12, 1997 "A team of scientists led by SFSU researcher Thomas B. Smith reports in the journal Science that ecotones, the transition areas between rain forests and savannas, may be integral to generating biodiversity in tropical rain forests.

Conserving these ecotones may be critical to preserving the processes that maintain diversity in rain forests, says Smith and his colleagues, Robert K. Wayne, UCLA; Derek Girman, SFSU Romberg Tiburon Center; and Michael Bruford, the Institute of Zoology, London.

"Ecotones are dynamic environments that have typically been overlooked," says Smith, an evolutionary biologist who specializes in the tropics. "The general belief is that if we preserve rain forests we're also preserving the processes that create biodiversity. But our findings suggest that the engines generating new species and increased biodiversity may lie in the unprotected ecotones at the forest periphery. "

Funded by the National Geographic Society, the National Environment Research Council of the UK, the World Wildlife Fund and the Royal Society, the 6-year-long study of West African rain forests and ecotones suggests a new paradigm for how biodiversity is generated.

Using molecular genetic techniques to examine the DNA of 12 populations of the little greenbul (Andropadus virens), a common West African bird species that inhabits both rain forests and adjacent ecotones, and by measuring their distinct physical characteristics, the team uncovered evidence linking ecotones with speciation.

"The findings are significant because they contrast with past theories of rain forest speciation which attribute the evolution to new species to geographic isolation, to the dynamics within the forest during glacial periods," says 41-year-old Smith. "Although much more work is needed, our results suggest that, instead, ecotones may be vital to the production and maintenance of biodiversity in tropical rain forests by creating new species through the process of natural selection."

In an accompanying Science news article, evolutionary biologist John Endler, who in 1977 was the first to suggest that natural selection may overcome gene flow, says Smith's work is "a major first step" in supporting the long-held hypothesis that natural selection not only shapes the physical appearance of all living organisms, but also may be important to the formation of new species.

From 1990 to 1996, the team compared birds from the forest and ecotone sites. Using mist nets to trap them, they drew blood for genetic analysis and measured five physical characteristics--weight, bill depth, and wing, tarsus and upper mandible length.

Smith found that although the ecotone populations were significantly different physically from their rain forest counterparts, there was considerable gene flow between them. Smith says this means that differences in natural selection may drive populations apart, despite gene flow.

"If new species are formed this way," reports Smith in Science, "they may move from their ecotone cradle to the forest and contribute to the biodiversity. If the work is confirmed by other studies, it may reinforce an idea that many biologists have suggested in the past, that rain forests are sinks for new species, rather than areas where new species are generated."

Rain forests contain 50 percent of the world's species, yet constitute only 7 percent of the earth's land mass. As forests shrink, says Smith, ecotones are some of the first habitats to disappear as a result of burning, wood gathering and grazing.

"If further research supports the role of ecotones as centers for speciation, they will need to be preserved," he says. "If we lose these habitats, we may be losing the processes that generate biodiversity."

Smith's team is continuing their work at 22 sites in West Africa. They plan to expand the study to include plants and mammals.

SFSU is a highly diverse community of 27,000 students and 3,500 faculty and staff members. It is the second largest of the nationally recognized 23-campus California State University System. Founded in 1899, the university is approaching its 100th year of service to San Francisco, the Bay Area, California and beyond.

- ### -

*Note to Reporters: Smith is an internationally recognized evolutionary biologist specializing in the tropics. He is available for interviews June 13 to June 18 by contacting Merrik Bush in the Office of Public Affairs: (415) 338-6747.

**Photos of the ecotones, the researchers and the greenbul are available upon request by contacting Merrik Bush. These images, along with the press release, are currently available for viewing on-line by accessing the SFSU Public Affairs Web site and selecting "Press Check-In":

San Francisco State University

Related Biodiversity Articles from Brightsurf:

Biodiversity hypothesis called into question
How can we explain the fact that no single species predominates?

Using the past to maintain future biodiversity
New research shows that safeguarding species and ecosystems and the benefits they provide for society against future climatic change requires effective solutions which can only be formulated from reliable forecasts.

Changes in farming urgent to rescue biodiversity
Humans depend on farming for their survival but this activity takes up more than one-third of the world's landmass and endangers 62% of all threatened species.

Predicting the biodiversity of rivers
Biodiversity and thus the state of river ecosystems can now be predicted by combining environmental DNA with hydrological methods, researchers from the University of Zurich and Eawag have found.

About the distribution of biodiversity on our planet
Large open-water fish predators such as tunas or sharks hunt for prey more intensively in the temperate zone than near the equator.

Bargain-hunting for biodiversity
The best bargains for conserving some of the world's most vulnerable salamanders and other vertebrate species can be found in Central Texas and the Appalachians, according to new conservation tools developed at the National Institute for Mathematical and Biological Synthesis (NIMBioS) at the University of Tennessee, Knoxville.

Researchers solve old biodiversity mystery
The underlying cause for why some regions are home to an extremely large number of animal species may be found in the evolutionary adaptations of species, and how they limit their dispersion to specific natural habitats.

Biodiversity offsetting is contentious -- here's an alternative
A new approach to compensate for the impact of development may be an effective alternative to biodiversity offsetting -- and help nations achieve international biodiversity targets.

Biodiversity yields financial returns
Farmers could increase their revenues by increasing biodiversity on their land.

Biodiversity and wind energy
The location and operation of wind energy plants are often in direct conflict with the legal protection of endangered species.

Read More: Biodiversity News and Biodiversity Current Events is a participant in the Amazon Services LLC Associates Program, an affiliate advertising program designed to provide a means for sites to earn advertising fees by advertising and linking to