NSF Award
0342538
The insect family Delphacidae, commonly called planthoppers, is a relatively large and widely distributed group of plant-feeding insects. The economic importance of planthoppers is well documented. The family includes at least 55 species that feed on economic plants and includes major pests of five of the top ten major world food crops, such as rice, sugarcane, maize, taro, and cereals. The importance of planthoppers as pests, particularly on rice, has driven research on their control. Plant damage results both from direct feeding and transmission of various plant diseases capable of causing millions of dollars of damage annually to the worldwide agricultural industry. Some planthopper groups tend to be specialist grass feeders (including cereal crop grasses), whereas other groups feed on sedges, rushes, and dicots. Based on environmental cues, nymphs of grass-feeding planthopper species develop into either short-winged or long-winged forms. Short-winged forms produce more offspring under favorable conditions, while long-winged forms are able to disperse into new environments when conditions are unfavorable. Despite the well-established scientific and economic importance of planthoppers, evolutionary relationships among planthopper groups are essentially unknown, effectively limiting biological studies on these insects. The purpose of this research is to reconstruct, using a combination of evidence taken from anatomical comparison and DNA analysis, the evolutionary relationships within the planthopper family Delphacidae based on a worldwide sample of these insects. By determining and interpreting planthopper evolutionary history in the contexts of geographic distribution and host plant association, the researchers will test their hypothesis that host plant shifts to grasses are responsible for the evolutionary success (i.e., greater diversity and range) of advanced planthoppers.<br/><br/>The understanding of planthopper evolution generated by this research will be of particular importance to the control of known planthopper crop pests, as well as for the control of future outbreaks of novel planthopper pests. This work will also provide a framework for integrating the considerable number of scientific studies that have been conducted on individual planthopper species. The researchers will also develop Internet accessible keys to aid in the identification of planthopper species; these keys will be of considerable value to both scientists studying these insects, as well as workers in agriculture environments affected by these insects. Additionally, the cutting-edge evolutionary analyses carried out through this research will serve as a model for similar studies on other plant and animal groups.
