The Genetic Basis of Mimicry in Bumble Bees
Open Access
- Author:
- Terranova, Tatiana
- Area of Honors:
- Biology
- Degree:
- Bachelor of Science
- Document Type:
- Thesis
- Thesis Supervisors:
- Heather M Hines, Thesis Supervisor
Stephen Wade Schaeffer, Thesis Honors Advisor - Keywords:
- Bombus
evo-devo
pigmentation genetics
Mullerian mimicry
color genetics
bumble bee - Abstract:
- Pigmentation provides an excellent phenotypic model for studying how genome-level mutations lead to phenotypic differences. Bumble bees are an emerging model for revealing the genomic potential for evolutionary change due to their exceptional color diversity and natural replicates driven by Mullerian mimicry. Two co-mimics are Bombus melanopygus, a red-black dimorphic species, and Bombus vancouverensis, a red-black polymorphic species. Previous work in B. melanopygus has revealed that major developmental Hox gene AbdB works as an upstream switch triggering downstream melanization shifts in the mid-abdomen and utilized transcriptomics to identify downstream pigmentation effectors at single developmental stage. In this thesis, I determine cross-developmental timing of these key coloration genes in B. melanopygus using RT-qPCR and compare these to the genes involved in parallel phenotypes across development in B. vancouverensis using transcriptomic data. AbdB was also found to be differentially expressed early in B. vancouverensis implicating a shared phenotypic switch and suggesting this is an evolutionary hotspot in Bombus coloration. nubbin, a wing development gene implicated in B. melanopygus coloration, was also found to be differentially expressed in B. vancouverensis , suggesting nubbin may play an intermediate developmental role across species. Both B. melanopygus and B. vancouverensis were found to trigger some of the same downstream core melanin genes, but varied in the roles of other genetic players. B. vancouverensis appears to rely on restriction of dopa via pale and upregulation of yellow to create black morphs, while B. melanopygus had some differential expression of pale but lacked yellow differential expression. For the red morph, both B. vancouverensis and B. melanopygus employ high differential expression of dopamine-reducer ebony, but generate red pheomelanin using different enzymes. Through comparing developmental gene expression of ebony, pale, AbdB, and nubbin, B. vancouverensis appears to “lag” behind in differential expression compared to B. melanopygus, a heterochronic switch which could explain the intermediacy in phenotypes found in B. vancouverensis compared to B. melanopygus. This thesis reveals the alternate genetic strategies to attaining convergent phenotypes and provides a framework for future comparative coloration work in these bees.