Insects which specialize in feeding on only certain groups of plants are important experimental organisms for addressing two fundamental questions in evolutionary biology. These are 1) what factors influence the appearance of new varieties or races of organisms? and 2) what factors determine the rate and direction of evolution? New varieties of insects have been found when new plants are introduced to or invade areas where an insect is already feeding on a related plant. Dr. Dingle proposes to study an insect species that feeds on various species of related plants and has switched in parts of its range to plant species that have been introduced as ornamentals. Dr. Dingle will study the evolution of the differentiation by examining the influence of genes and the environment on this evolution. Dr. Dingle will also examine the basis of host choice in the two populations and test to see if the two populations will still interbreed. In this way Dr. Dingle will attempt to learn if the two populations have differentiated enough to be separate species. The problem of adaptation to new host plants is of considerable basic and practical importance. Most important crop plants are introduced and it is important to know how readily insects can adapt to them and become pests. Many alien plants are accidentally introduced and may thus "escape" the insects which normally feed on them to become abundant weeds. To control them it is useful to know how readily new insects can adapt to them and replace the natural enemies they left behind. The insect studied here is particularly useful because the effect of a switch in host plants, a dramatic change in mouth part structure, is so easy to measure and manipulate. As a result of this switch, the insect has evolved changes in the structure of mouth parts used in feeding on the different plants. The research thus holds great potential for minimizing insect damage to introduced crops and to maximize damage to introduced weeds.
