Host Plant Phenology and Insect Speciation

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9509125 WOOD Many insect species are restricted to feed on specific host plants. How this specialization comes about, whether it is a requisite for speciation and whether it requires geographic isolation are open to debate. When insects acquire novel host plants it is important to understand the mechanisms and consequences, for a number of reasons. Changes in host plant usage occur in natural communities and thus are important factors in attempts to understand the origin / structuring of insect-plant communities and geographic patterns of insect species diversity. If a new host plant is commercially important, the result is often the creation of a new pest. In cases of existing pest species such host plant changes can lead to genetic alterations between populations on different plants that require new management practices. Thus to understand natural and managed plant communities the processes that initiate and the ultimate consequences of insect shifts to new host plants must be understood. In this proposal insects from a single population will be manipulated by placing them in seven different environments. Each environment consists of different combinations of natural and novel host plants. Three environments consist of novel and natural hosts which allows the determination of whether divergent host specialization can occur when there is potential free insect movement between host species. The remaining environments are to examine the process of host specialization when free insect movement between natural and novel host plants is prohibited. The experiment will be done in the field utilizing 28 large screened walk-in rooms. Each of the seven environments will be replicated four times. Variables to be examined will be host plant species effects on insect life history timing of egg hatch, mating, and egg deposition. At each of these life history stages differential host effects on survival will be determined. The extent of movement between hosts within each of the seven enviro nments will be determined using marked insects.