NSF Postdoctoral Fellowship in Biology FY 2019: Mitochondrial genome architecture as a driver of speciation in parasitic lice

Sweet Andrew D, Urbana IL

Investigators

Abstract

This award supports an NSF Postdoctoral Research Fellowship in Biology, Research Using Biological Collections. The fellowship supports research and training of the fellow that will utilize biological collections in innovative ways. Most animals have mitochondrial DNA on a single chromosome. However, some species of parasitic lice have their mitochondrial DNA separated onto multiple chromosomes. It is not known how or why such a rare condition is maintained in lice. The fellow seeks to address this knowledge gap by testing whether differences in mitochondrial genome architecture (that is, single vs. multiple chromosomes) are linked to natural selection and speciation, the processes largely responsible for generating biodiversity. To this end, the fellow will rely on museum collections to compare DNA sequences and body measurements of lice species that have multiple mitochondrial chromosomes to those that have a single chromosome. This work will help answer a particularly puzzling question in biology while simultaneously showing a mechanism that generates biodiversity. The project will also include educational components that promote biodiversity among general audiences at both local and national scales. The fellow will use multiple lines of evidence obtained from museum specimens to specifically address whether fragmented mitochondrial chromosomes act as a buffer to speciation via mito-nuclear incompatibility. First, the fellow will compare phylogenetic diversity, mutation rates, and genomic selection in two groups of avian lice that are known to have different mitochondrial architectures: wing (fragmented chromosomes) and body (single chromosomes) lice from doves. Lower mutation rates but higher diversification, divergence, and selection in body lice would suggest that single mitochondrial chromosomes promote speciation. Second, the fellow will test mutation rates and levels of selection in cryptic species of lice. Cryptic species have indistinguishable morphological differences but are highly divergent genetically. If pairs of cryptic body louse species have inseparable morphology with high genetic divergence and signatures of positive selection, whereas cryptic wing louse species do not, this would again indicate that single chromosomes promote speciation. The fellow will receive extensive training in morphology-based inquiry and genome evolution. This project will also include a component for training Purdue University undergraduate students in molecular/bioinformatic methods. Additionally, results from the work will be incorporated into lesson plans, outreach displays, and educational publications focused on evolution and biodiversity. This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.