DEVELOPMENTAL EFFECTS OF THE INTERACTION BETWEEN EVOLUTION, DIET, AND THE MICROBIOME

Abstract

Phenotypic variation is generally thought of resulting from the combined effects of genetics and environmental variation. However, in recent studies, the role of the microbiome has become more apparent, providing insight into phenotypic changes in hosts. Genome Wide Association Studies (GWAS) have further uncovered genetic alterations in D. melanogaster that point towards microbial genetic influence on host phenotype, thereby suggesting its prominence in studying factors driving phenotypic variation. There is currently a lack of studies investigating the interaction between host genetic variation, microbiome genetic variation, and environmental variation. This thesis aims to address this gap by providing information on these integrated effects on phenotypic variation. Using D. melanogaster as a model, twelve permutations of treatments based on High Sugar (HS) or Control (C) diets, HS or C microbiomes, and flies derived from HS or C evolutionary lines were studied in three separate trials. The results demonstrate a strong correlation between diet and developmental time, as well as a combinational association between fly evolutionary line and food type with developmental timing. The effects of the microbiome were less apparent. These results on development may be attributed to decanalization and stress-related effects of a High Sugar Diet. Further research is necessary to quantify bacterial genomic correlations with host genome for HS and C fly lines to quantify the role of diet on the host and bacterial genomics. Additionally, understanding other phenotypic effects such as nutritional indices would be beneficial for revealing the extent of the interplay between host genetic variation, microbiome genetic variation, and environmental variation on phenotypic variation (Vp = VG-host + VG-micro + VE).