Getting the picture: Hawaiian picture-wings are among the most remarkable of the islands' 10,000 native insect species.
Picture-wings are part of the Hawaiian Drosophilidae family, widely considered the most remarkable and intensively studied group of the state's nearly 10,000 native insect species. More than 500 species of Drosophilidae have been named and described; an additional 250 to 300 await identification at the University of Hawaii.
Drosophilidae--both its Drosophila and Scaptomyza genera--are renowned in the scientific community. The flies are viewed as model organisms. The genera help scientists better understand how new species are formed. New theories of evolutionary biology have been developed and tested as a result of research that has been conducted on the Drosophilidae family, particulary picture-wings, part of the Drosophila genus.
"Research on this group of insects from every aspect of biology has enabled scientists to not only test classical concepts of biology, but, more important, it has provided an opportunity to formulate new ideas," says Dr. Kenneth Kaneshiro, director of the Center for Conservation Research and Training at the University of Hawaii.
"This group has been recognized as one of the best groups for investigating the dynamics of evolutionary process," he says. It has been illustrated in biology texts as examples of historical biogeography and the radiation of species.
Although the Drosaphilidae family may be represented by more than 1,000 species, some of those individuals' numbers are falling. Picture-wings, like numerous Hawaiian species--25 percent of the country's endangered and threatened plains mad birds are found in Hawaii--are one such example. Some scientists worry that the species eventually could be eradicated.
Biologists at the University of Hawaii and the Pacific Island Ecosystems Research Center have surveyed picture-wings in Hawaii Volcanoes National Park since 1971. Results suggest a long-term decline for many species. Some populations are so small they could be eliminated by a natural event such as a hurricane.
In January 2002, the U.S. Fish and Wildlife Service announced plans to list 12 species of picture-wings as candidates for the Endangered Species list. Several other species were named shortly thereafter, expanding the candidate list to 15. Researchers believe that number could grow to 50 once more data are gathered.
About one-third of the world's Drosophila including picture-wings, occur only in Hawaii. The species are located throughout the high islands of the Hawaiian archipelago, a group of 132 islands, reefs, and shoals that includes Halcakala and Hawaii Volcanoes national parks and stretches some 1,500 miles.
Each picture-wing proposed for listing as endangered is found on only a single island. Each breeds in only one or a few related plant species, some of which also are threatened or endangered.
Several species of picture-wings are found within certain areas in Haleakala National Park. They are more widespread in Hawaii Volcanoes National Park. The flies are associated with native plants in both wet and dry conditions in both parks.
The species are restricted to native Hawaiian ecosystems, most of which are found in higher elevations with cooler temperatures, and likely could not survive outside of such habitats. If, say, the male flies are exposed to temperatures above 70 degrees Fahrenheit, even for a few minutes, they could become sterile.
Individual species, however, have adapted to various environments within the ecosystems. Some occupy dry forests; others live in rainforests. For this reason, biologists and scientists believe that picture-wings represent an extraordinary case of habitat-specific evolution, perhaps more than any group of animals in the world.
"Any impact on these native ecosystems will have consequences on these insects," says -Kaneshiro, "which are, for most of the species, [already] found in relatively low population sizes."
Hawaiian Drosophila became threatened when humans and invasive alien species, such as the non-native western yellowjacket wasp, began to inhabit the islands, according to Kaneshiro. Habitat degradation caused by alien weeds mad wild animals, such as mouflon sheep, deer, and pigs, also have contributed to the species' declining numbers. Habitat lost or "damaged because of fire, biological pest control, and predation from alien insects, particularly ants and wasps, have played a part in the picture-wings' threatened stares, as well.
Collectively, picture-wings, often referred to as the "birds of paradise" of the insect world because of their spectacular courtship displays, are the largest Drosophila species, although their morphologies, size, and color are varied.
Many are about the size of common houseflies, mammoth compared with their mainland relatives, with wingspans exceeding 20 millimeters. Others are extremely small, with less than a five-millimeter wingspan. Some are a shiny black with no markings on the wings, while others have color patterns on their body; abdomen, and head mad elaborate markings on their wings.
The flies have three main body parts: a head, thorax, and abdomen. Two antennae protrude from the front of the head between their eyes. Their wings mad three pairs of legs are attached to the thorax.
Their lifespan varies, depending on the species. Some live only a few days, whereas others live close to a year and are sometimes kept alive in a laboratory.
Hawaiian picture-wings and other Drosophilidae have supplied the scientific community, and the general public, with a wealth of biological knowledge over the years.
"The results [of research on the genus] have been applied to ... controlling agricultural pests, such as tephritid fruit flies Mediterranean fruit fly; Oriental fruit fly--and we are now beginning to use these flies for biomedical and pharmaceutical research," Kaneshiro says.
Protecting the picture-wing species, and the rest of the Drosophilidae family, by preserving and restoring its natural habitat and eliminating invasive alien species is vital. The benefit to human-kind is too great not to.
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|Title Annotation:||Rare & Endangered|
|Date:||Jan 1, 2004|
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