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The whitefly sibling species group Bemisia … The whitefly sibling species group Bemisia tabaci (Genn.) (Hemiptera: Aleyrodidae) is the most important whitefly pest worldwide, causing millions of dollars in damage by reducing crop (floricultural, horticultural, fiber) yields each year worldwide. It colonizes a large number of non-agricultural eudicot species, and is the sole insect vector for the largest known group of ssDNA plant viruses (genus Begomovirus) that infect endemic as well as cultivated plants. The group is so named because it is considered, but not demonstrated genetically or in any other satisfactory way to comprise a group of variously related strains (races, biotypes) and perhaps even closely related species. Members of the group are indistinguishable morphologically, making them difficult to control at the level of selective ‘exclusion’ (economic, regulatory), and also making them a fundamentally interesting group from an evolutionary standpoint since they can only presently be distinguished on the basis of a suite of phenotypes and an informative molecular marker. Phenotypic variation is manifest in differences in invasiveness, fecundity, host preference/range, long or short distance flight behavior, extent of reproductive isolation, suite of endosymbionts (some whose HSP aids in whitefly-mediated virus transmission), insecticide resistance, vector competency, and in ability to cause phytotoxic disorders caused solely by feeding. They are loosely ‘identified’ and categorized phylogeographically based on the mt-COI gene, the most informative of several molecular markers studied so far. Examination of microsatellites (STRs) and other population-informative loci (RAPDs, AFLPs) show concrete evidence of high genetic differentiation and complex population structure among and within clades. Tight phylogeographical distribution, high genetic differentiation, together with structure within populations are consistent with the ability of B. tabaci to adapt to a broad range of ecological environments spanning tropical, subtropical, and mild temperate climes around the globe. Whether phenotypic plasticity is driven by genome-level differentiation (mutation and corresponding evolutionary changes in protein coding), or at the physiological level e.g. modulation of gene expression, and/or epigenetic regulation is not known, but could be informed by sequencing and analysis of multiple exemplar genomes of this widely studied sibling species group. Furthermore, how associated endosymbionts (horizontally and vertically transmitted) contribute to plasticity or to adaptations that may require cooperative gene product interactions between the unrelated prokaryotic genomes and/or the eukaryotic (insect) genome, are entirely unstudied. Consequently, the B. tabaci sibling species group provides an exquisite model for elucidating gene networks and functional mechanisms that drive the phenotypic plasticity in this ancient whitefly group, at times leading to biotype formation, and likely also to recent speciation, in some instances. This new knowledge will open uncharted avenues toward understanding the genomic features that influence the evolutionary and population biology of insect sibling species, endosymbiont-host evolution, and virus-vector interactions. Knowledge gained will readily have application to understanding the genomics contributions to biology and evolution in other sibling species groups and complexes, both within and outside of the Hemiptera. The proposed effort would best be undertaken as a comparative one, involving sequencing multiple genomes (up to 10) of genetically and behaviorally divergent B. tabaci haplotypes worldwide.
Note: I am willing to coordinate procurements of a diverse suite of B. tabaci biotypes and haplotypes representative of this sibling species group from different continents and (agro+) ecosystems. fferent continents and (agro+) ecosystems.
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