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Evolutionary Biologist Discovers Missing Pieces of
the Evolutionary Puzzle in Ant Evolution
SAN FRANCISCO, CA (January 8, 2001) ó In one of the last remaining high plateau forests in Madagascar just outside Antananarivo, the country's capital, Academy Entomologist Brian Fisher recently discovered rare ants that could provide a critical piece of the puzzle of ant evolution. Fisherís find, an intact colony of a new type of ant in a rare group he has dubbed Dracula Ants, were living in a rotting log in an unprotected mountain rainforest. The new species may be the evidence evolutionary biologists need to understand the origin and evolution of ants and their social behavior.
Ants are arguably one of the most ecologically and numerically dominant families of organisms in almost every terrestrial habitat throughout the world, though they include only about one percent1 % of all described insect species. A major obstacle to understanding the evolution of ants from wasps has been the inability to clearly determine their primitive characteristics, which requires identifying the basal lineages within the ants (that is the nearest relatives to remaining ants). The abdomens of Dracula Ants resemble wasps more closely than most other ant species. Based upon initial studies, these ants are of a primitive lineage, and potentially the nearest relative of all other living ants. "These ants also pack a powerful sting much like the wasp," says Fisher. "If you do get stung by one of them, youíre one of the only people in the world to have had it happen."
The genus of the species was first identified in 1993 when scientists found several worker ants and were fascinated by the odd combination of primitive characteristics. "It was one of the most perplexing finds in Madagascar," explains Fisher. "Based on the collection of a few workers, we were pretty sure the existing hypotheses of the evolution of ants were wrong. However, it was impossible to understand the genus and propose a more accurate evolution of ants because we werenít able to find an intact colony, consisting of males, pupae and a queen."
Fisherís unprecedented capture of these ants, belonging to the rare genus Adetomyrma, will provide the first opportunity for scientists to study this enigmatic species, which is critical for understanding ant evolution. With only 282 known genera of ant species in the world, the discovery of a new genus is extremely uncommon. "The importance is not that these ants represent a new species, or a recently discovered genus, itís their implication for ant evolution. These ants are a classic example of a relic genus," he explains. "Madagascar, as an island, has evolved uniquely for a very long time, and so, the organisms on the island may represent pieces of the evolutionary puzzle that have gone extinct elsewhere. Whereas you might find one genus of ant both in North America and on the African continent, you wonít find Adetomyrma anywhere except on Madagascar, maybe even in this one specific forest region."
Fisher has observed queens of this rare group of ants cutting holes into their own larvae and sucking the hemolymph (insect blood), thus earning them their nickname, Dracula Ants. Using their mandibles, which Fisher points out look much like gardening tools, workers in some species stun prey, such as centipedes, with venom and bring larvae to feed on the catch, at which point the adults feed upon the larvae without killing them. Colonies of this strange new species may contain more than 10,000 workers, multiple wingless queens, and winged males.
A lucky set of circumstances allowed Fisher to discover these colonies of Dracula Ants. The endemic species was found in an unprotected forest about 90 kilometers from the capital city, an area tremendously threatened by deforestation. The proximity of the population to the capital makes this species vulnerable to the onslaught of an enemy exotic ant, which has perhaps already eclipsed other unknown species on the island.
The World Wildlife Fund and Conservation International have long recognized Madagascar as a "bio-diversity hotspot" as many of the islandís species are endemic, found nowhere else on Earth. Deforestation, erosion, desertification, and loss of natural habitat have plagued the island republic. Almost 85% of the natural forest has been lost in the last 20 years, yet no single factor, group of people, or economic scheme is to blame.
Fisher, Assistant Curator of Entomology, began his research in 1992 and estimates that he has discovered over 600 new species of ants on the island.