Comparative Transcriptomics and GWAS across North American Pyrobombus
In the bumble bee subgenus Pyrobombus, a largely North American lineage, several major groups mimic each other across Western American mimicry complexes, with black forms attained in Pacific coastal regions and red forms attained in the Rocky mountain distributions of these taxa. These species have intervening taxa in the phylogeny that have different patterns and thus could involve different loci or sorting of ancestral variation. We perform genome sequencing and a genome wide association analysis in males of both color forms in B. Vancouverensis to identify gene elements initially driving the variation and enable comparison in loci involved in the same polymorphisms in co-mimicking species. This species presents additional challenges to comimics such as B. melanopygus as the color is continuous between the two forms, suggesting regulation may be multigenic. We also examine the genes driving differential coloration across three sets of comimicking pairs (B. vancouverensis red and black form, B. melanopygus red and black form, sister species pair B. huntii (red) and B. vosnesenskii (black)) using RNA-seq differential gene expression analysis across developmental stages spanning the start (P15 pupation), middle (0hr of eclosion), and late stages (12 hr after eclosion) of coloration. With this system, we examine how gene expression of red/black epidermal segments shifts across the lineage, to determine (1) which genes are changing to generate these phenotypes, (2) whether the same genes or different genes of the same gene networks are implicated in repeated phenotypes, and (3) how expression and roles of core regulatory genes shift across the clade. Two sister group lineages that are black form were also analyzed for their transcriptomes: B. impatiens (P15, 0hr, 12hr) and B. bimaculatus (P15, 0hr), to assess evolution of gene expression patterns. In addition to our current transcriptomics data, we are also utilizing the raw sequencing files from a previously published bioproject for Bombus melanopygus (PRJNA721780).