 |
|
|
Tropical Scientists Find Fewer Species Than ExpectedMINNEAPOLIS / ST. PAUL -- An eight-year National Science Foundation-funded study of New Guinean rainforest plants and the insects that feed on them has yielded a new and dramatically lower estimate of the number of species on the planet. The estimate, which lowers the number of species from approximately 31 million to between four and six million, is based on the finding that insects specialize their feeding not on individual species of plants, but on genera and even families of plants. In "bringing some reality" to estimates of world biodiversity, the study allows scientists to get a better handle on how fast species are being lost, said University of Minnesota plant biologist George Weiblen, the principal plant expert on the research team. The work will be published in the April 25 issue of Nature. It is important to know how fast biodiversity is being lost, but this is hard to gauge without a solid baseline, Weiblen said. Scientists advising governments on policies to curtail species losses must have credible estimates of species numbers if they are to shape appropriate policies. The stakes are high because losses of too many species or certain kinds of species can cripple tropical forest ecosystems, which normally stabilize soil and climate, purify and recycle water, and produce food, medicine, building materials or other useful products, he said. The current study took a cross-disciplinary approach; besides Weiblen, the principal scientists were insect expert and project coordinator Scott Miller of the Smithsonian Institution and insect community ecologists Yves Basset of the Smithsonian Tropical Research Institute in Panama and Voytech Novotny of the Czech Academy of Sciences. The team compared insect communities feeding on 51 tropical plant species, most belonging to either the fig family, the mulberry family or the coffee family. While previous work had also based estimates of total species on numbers of insects--the most species-rich class of animals known--scientists had assumed that each plant-eating insect species tended to feed on one or very few plant species. If true, the estimates of the number of herbivorous insects should be tied to the number of plant species. "Instead, most insects turn out to be specialized not to plant species, but rather to a genus [grouping of species] or family [grouping of genera] of plants," Weiblen said. "Fewer effective plant 'hosts' means fewer herbivores. Where people had assumed that different insects' food sources overlapped very little, we found that many insects share their food plants with other insect species. There are actually few extreme specialists among tropical insect herbivores." New Guinea's species diversity made the island an ideal laboratory for the study. Its tropical forests are about the same area as Texas but contain five percent of the world's biodiversity, Weiblen said. The island has 12,000 species of plants; in comparison, Weiblen's home state of Minnesota has only about 1200 species. The work began in 1994 with studies of the insects eating 15 species of figs--Weiblen's area of specialty--that co-occur in the rainforest. The study then expanded to include the mulberry family, which is related to figs, then members of the coffee family and more distantly related plants. The team used DNA sequences to sort out the evolutionary relationships between plants and looked at how insect species were distributed on them. They found that the tropical forest plant community was dominated by clusters of closely related plant species and that insects tend to feed on multiple close relatives in a given plant genus or family. Because the number of insect species was tied to broader--and therefore less numerous--categories of plants, estimates of their numbers had to be diminished, Weiblen said. Once the estimate of herbivorous insects had been made, the researchers plugged that number into equations to estimate the total number of species in the world. Such equations take into account the proportion of insects that are herbivorous, the proportion of all species that are insects or other members of the arthropod group, the proportion of all plant species that are found in New Guinea, and other factors. Depending on whether insects as a whole follow the pattern of beetles, whose food preferences are quite broad, or moths and butterflies, which are more particular, they estimated that the world contains a total of between about 4.8 million and 6 million species. "Our estimates bring some reality to predictions about declining biodiversity in the sense that the consequences for insect herbivores of losing a particular host plant species may not be as dire as previously thought," Weiblen said. "But that is no reason to ignore the decreasing number of species worldwide. [Harvard biologist] E.O. Wilson predicted in his book 'The Future of Life' that half of all species will suffer extinction in 50 years if current land use patterns continue. Because the consequences are so severe, we've got to refine our predictions and conserve as many species as possible."
Can't find it? Try searching ScienceDaily or the entire web with: |
Science Video News
Hawaii's Kilauea volcano is once again putting on a show. > watch video
A local zoo showcases baby leopards, the first to be born in a South Korean zoo. > watch video
A new report finds that in the Northern Hemisphere, average global surface temperatures climbed... > watch video
Related News Topics> more ...
Related Science Stories> more ...
Related Encyclopedia Articles> more ...
Related Book ReviewsRain Forest Insects Eat No More Tree Species Than Temperate Counterparts (August 24, 2006) -- A study initiated by University of Minnesota plant biologist George Weiblen has confirmed what biologists since Darwin have suspected -- that the vast number of tree species in rain forests accounts ... > full story
New Areas Of High Biological Diversity Discovered (May 21, 1999) -- By concentrating on the humble terrestrial flatworm, biologists from the Zoological Museum at Amsterdam University (UvA) have discovered three new "hotspots" of biological diversity: New Zealand, ... > full story Plants, Insects Play Cat And Mouse Game (October 25, 2001) -- Plants and insects play a far more intricate game than we suspect, says a University of Toronto researcher in the journal Science this month. Likening the game to one of cat and mouse, botany ... > full story
A 300-Million-Year Old Twosome: The Cycad And Its Pollinator (August 6, 1998) -- Living fossils of the plant world, the cycads can trace their lineage back to about 300 million years ago. In a world without flowers, forests of these palm-like plants were the main feature of the ... > full story Just How Many Species Are There, Anyway? (May 26, 2003) -- One barrier to protecting biodiversity is that there are no good ways of figuring out how many species there are in large areas. Now we may finally be able to find out: a new method accurately ... > full story Plant Detectives Seek Sources Of Invasive Trees (August 13, 2002) -- Barbara A. Schaal, Ph.D., Washington University professor of biology and her graduate students use DNA sequences to reveal information on historical events. Schaal has traced the origins of cassava ... > full story Wildlife gardening -- Wildlife gardening is a school of gardening that is aimed at creating an environment that is attractive to various forms of wildlife such as birds, amphibians, reptiles, insects, mammals and so on. A ... > full article Trophic level -- In ecology, the trophic level is the position that an organism occupies in a food chain - what it eats, and what eats ... > full article Transgenic plants -- Transgenic plants are plants that have been genetically engineered, a breeding approach that uses recombinant DNA techniques to create plants with new characteristics.They are identified as a class ... > full article Pitcher plant -- Pitcher plants (or pitfall traps) are carnivorous plants whose prey-trapping mechanism features a deep cavity filled with ... > full article Biodiversity hotspot -- A biodiversity hotspot is a biogeographic region that is both a significant reservoir of biodiversity and is threatened with ... > full article Biodiversity -- Biodiversity or biological diversity is the diversity of life. There are a number of definitions and measures of biodiversity. One definition of a biodiversity hotspot is a region with many endemic ... > full article Deciduous -- In botany, deciduous plants, principally trees and shrubs, are those that lose all of their foliage for part of the ... > full article Purple loosestrife -- Purple loosestrife is a semi-aquatic herbaceous plant belonging to the loosestrife family, Lythraceae, native to the wetlands of Eurasia. It is a herbaceous perennial plant, growing 1-2 m tall, ... > full article Forest -- A forest is an area with a high density of trees. These plant communities cover large areas of the globe and function as carbon dioxide sinks, animal habitats, hydrologic flow modulators, and soil ... > full article Phytopathology -- Phytopathology or plant pathology is the science of diagnosing and managing plant diseases. It covers all infectious agents that attack plants and abiotic disorders, but does not include herbivory by ... > full article
|
