Indiana University-Purdue University Indianapolis (IUPUI) / Development rate is a quantitative trait that displays significant variation within many species, including Cochliomyia macellaria Meigen (Diptera: Calliphoridae). Calliphorids are a family of dipterans known as blow flies and are commonly used in forensic entomology to estimate the minimum postmortem interval (PMIMIN), given some assumptions are made. In order to dissect the genetic underpinnings of development rate variation in this species, artificial selection for fast and slow development with population-based resequencing was used. The objective of this study is to isolate and characterize genomic regions that are correlated to development rate variation in blow flies. The first approach used known regulatory development genes from Drosophila melanogaster Meigen (Diptera: Drosophilidae) and isolated variants that were associated with development time changes in artificially selected fast and slow development C. macellaria strains. Three variants located in Ras and Eip74EF were associated with fast or slow development in selection strains with a significant change in allele frequency. The second approach involved the comparison of pooled artificially selected fast and slow C. macellaria genomes to investigate the genetic basis of development rate variation. When comparing the fast and slow genomes, 699 sequences were identified that contained 7290 variants with consistent changes in allele frequency. The variants indicated that the genomic regions that are associated with development rate were associated with developmental processes, including regulation of RNA polymerase II activity, and transporter activity, such as protein dimerization. Of the 699 sequences, 69 sequences were related to Achaete-scute complex and 14 were related to Cyp12A7. The identification of the genomic regions that associated with development rates from this study provides an important resource for future studies in identifying potential genetic markers to increase the effectiveness of PMIMIN estimates. By using significantly associated variants as a priori candidates for future studies, the data increases the understanding of natural development variation in blow flies.

This research explores the capacity for functional photoreception in larvae of the mountain pine beetle (Dendroctonus ponderosae), an extremely important forest pest insect that is well adapted for development beneath the bark of pine trees. Phototaxis tests, gene expression analysis and development experiments were integrated to assess mountain pine beetle larvae for light sensitivity. When presented with a phototaxis choice test, larvae preferred dark over light microhabitats, revealing that larvae sense and respond behaviourally to light. Long wavelength opsin transcription was identified in all life stages, including eggs and larvae, suggesting that D. ponderosae possesses extraretinal photosensitive capabilities across its life cycle. The long wavelength opsin could function in phototaxis or the development phenology of immature beetles, while the ultraviolet opsin, only found to be expressed in pupae and adults, is likely to function in dispersal via the compound eyes. Results from two development experiments reveal an effect of photoperiod treatment on beetle development rate when reared from the egg stage, but not when reared from mature larvae, indicating that a critical photosensitive life stage(s) must occur in D. ponderosae prior to the third larval instar. An effect of photoperiod on adult emergence rates, however, appears to be independent of larval rearing conditions. The discovery of opsin expression and negative phototaxis in eyeless mountain pine beetle larvae, in addition to an effect of photoperiod on immature development and adult emergence rates, suggest that light and photoperiodism likely function in survival and life cycle coordination in this species. / Graduate / 2018-10-17

No description available.