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Population genetics of mosquitoes (Diptera: Culicidae): Investigate the population genetics and breeding structure of mosquito vectors of human malaria in Asia using multilocus genotyping. Human malaria in Asia is making a comeback due to a number of factors. Conventional management of disease transmission is becoming increasingly difficult because of insecticide resistance evolution in mosquito vectors and drug resistance in the parasites. Therefore, the use of genetically modified mosquitoes is being considered. We believe that a thorough understanding of the population genetics of the primary vectors of malaria in Asia is essential for both conventional and GM-mosquito based management strategies.<P> The main hypothesis to be addressed is: the use of multilocus genotyping and landscape genetic analysis enables the identification of cryptic genetic discontinuities - breaks in gene flow without obvious cause - or secondary contact among previous isolated populations, information which can then be used for identifying breeding units. These breeding units are then targeted using wither conventional methods of management or GM mosquito releases. <P>Wood roaches (Cryptocercidae: Dictyoptera): Characterize patterns and levels of variation among populations of the wood-feeding cockroach, Cryptocercus, from the eastern and the western U.S. using mitochondrial and nuclear DNA sequences. Kambhampati et al. (1996) showed that sequence divergence in mitochondrial rRNA genes was consistent with that among congeneric insects. Aldrich et al. (2004a) described morphological variation among three new species of Cryptocercus described by Burnside et al. (1999) from the eastern U.S. Studies are now underway to quantify the breeding structure of Cryptocercus species using protein and DNA sequence analyses. The data are expected to provide insights into the evolution of eusociality in termites since Cryptocercus are evolutionarily closely related to termites. We hypothesize that there is high levels of inbreeding among individuals in a log which leads to high relatedness and could be a prelude to cooperation. <P>Genomics of termites (Isoptera): We are undertaking large scale genomic studies on the termite Reticulitermes flavipes with the ultimate aim of understanding the genetic basis of eusociality and caste differentiation. We have initiated expressed sequence tag (EST) analysis from cDNA libraries constructed from workers, soldiers, alates, and larval stages. We will fabricate microarrays with 5000 genes and undertake a detailed analysis of differential gene expression. Finally, we will be constructing a BAC library and sequencing 10 random clones to obtain an initial characterization of the termite genome. Our hypothesis is that caste differentiation is underlain by the differential expression of many different genes and that the gene expression patterns can be identified using microarrays and related to differences in caste morphology, behavior, and physiology
Non-Technical Summary: How insect populations are structured in space and time is of direct relevance to their management. Examples: How genes that confer resistance to insecticides among different insects in different geographical locations is determined by their ability to migrate, which can be estimated by our approach. The project will generate information on the population genetics and evolution of insects. Examples: This project examines the population genetics of mosquitoes that transmit human disease and this information can be used to control such mosquitoes and reduce disease prevalence. This project will study the genes that underlie termite development and behavior; these genes can be targeted for termite control. <P> Approach: This project will entail the use of multilocus genotyping and genomics to study the population genetics and genomics of insects, respectively. For population genetic studies, microsatellites will be developed for each insect species to be studied. Samples of insects will be collected at the appropriate locations, brought to the laboratory and assayed for genetic variation. The data will be analyzed standard population genetic methodology as well as tests for specific questions to be addressed for a given species. For genomics, we will use two approaches. cDNA libraries will be constructed and 15000-20000 clones will be sequenced at random. These sequences (ESTs) will be analyzed using various genomics and bioinformatics tools to identify their function. The ESTs will then be spotted onto a microarray slide and used in studies of differential gene expression among various termite castes. A second approach will be the use of a BAC library which will include, in small pieces, the entire genome of the insect. A subset of these BAC clones will be sequenced to obtain an initial characterization of the genome. Future efforts will be directed toward obtaining the complete genome sequence of the insect (in this case, a termite).