Scott Miller, NMNH insect taxonomist, remarked: It is amazing how few of the original assumptions have been tested in the last 20 years, despite a great number of general papers discussing the overall numbers. The work published this week in Nature estimates 3.7 to 5.9 million insects, much closer to estimates based on total numbers of insects represented in regional collections. The PNG study found very few species of moths, butterflies, beetles or grasshoppers and their relatives restricted to a single host plant species, but instead, so-called specialized species ranged across a plant genus.
The study emphasizes host-herbivore relationships with respect to phylogenetic relationships between host plants. Closely related tree species share around 50% of their insect herbivores. Large, speciose genera supported more distinct herbivore communities than did smaller genera. Even distantly related plant hosts shared up to a third of their leaf-feeding insects. Because species-rich genera dominate extremely biodiverse tropical forests, the group postulates that specialist herbivores are probably rare. Therefore, they regard genera rather than species as the preferred unit to use in biodiversity calculations and choose to multiply the numbers of insects collected per tree by the estimated total number of genera in New Guinea, rather than by total number of tree species to arrive at the grand total.
Between one and two million insects have been identified to date (funding for a complete catalog to summarize information from collections worldwide is lacking). Only about 10,000 are added each year. At this rate, it will take another 200-400 years to identify the rest (assuming their habitat is not destroyed in the meantime).
In order to understand life on this planet, there is an urgent need to speed up the process of identification. Miller, who develops databases for big collections, said: If you can create
Contact: Michele Urie, NMNH Office of Public Affairs
Smithsonian Tropical Research Institute