Unnoticed by the nearby residents of St. Johnsbury, Vermont, tiny leaf beetles that flit among the maple and willow trees in the area have just provided some of the clearest evidence yet that environmental factors play a major role in the formation of new species.
At Vanderbilt University, graduate student Scott Egan and his adviser Daniel Funk, associate professor of biological sciences, obtained this new evidence from an experimental study published online this week in the early edition of the Proceedings of the National Academy of Sciences.
Funk has investigated this odd group of leaf beetles (which resemble unappetizing caterpillar pellets) for 15 years. In recent years he and Egan have used Vermont populations that associate with red maples and Bebbs willows to investigate how divergent ecological habits promote speciation. Their past observations have suggested that such "maple leaf beetles" and "willow leaf beetles" may be in the process of dividing into two new species: Each prefers to feed and lay eggs on their own "host plant," where they grow and survive best. Although there is some intermixing, the beetles show a decided preference for mates from the same host. While maple and willow beetles are visually indistinguishable, the current degree of their divergence is highlighted by the willow beetles' willingness to starve to death rather than feed on the maple leaves readily consumed by their maple beetle cousins.
This research has established these inconspicuous beetles as an important example of how ecological factors contribute to evolutionary divergence and the origin of Earth's millions of species. "Without this process, life would not have the incredible number and variety of species that we take for granted," says Funk.
Although such ideas were raised just after Darwin wrote his famous book, On the Origin of Species, most 20th century research focused on the role of genetic factors and geog
|Contact: David F. Salisbury|