Host-parasite co-evolution of Drosophila innubila and its parasites
Though Drosophila melanogaster is a staple system for studying evolution, little is known about its ecology. Additionally, Sophophora (the group containing D. melanogaster) represents only ~300 of the Drosophila species, compared to the ~1400 Drosophila in the sister clade. Mycophagous Drosophila have been extensively studied ecologically for ~40 years, are highly diverged from D. melanogaster, and are preliminary models for the evolution of toxin-tolerance, immunity, host-parasite evolution and behavior. I study D. innubila, a species of mycophageous Drosophila of particular interest due to its high frequency infection by a DNA virus and a male-killing Wolbachia. I’m particularly interested in identifying novel methods of parasite regulation, outside those characterized in D. melanogaster. I also examine the evolution of Drosophila innubila Nudivirus (DiNV), the parasite infecting D. innubila, I find two competing viral haplotypes with differing viral titers and differing rates of transmission. These two viral types are maintained against each other due to a trade-off between transmission and virulence.
- Unckless (2011), A DNA virus of Drosophila.
- Hill and Unckless (2017) Baculovirus Molecular Evolution via Gene Turnover and Recurrent Positive Selection of Key Genes.
- Hill and Unckless (2018) The dynamic evolution of Drosophila innubila Nudivirus.
- Hill, Koseva and Unckless (2019) The genome of Drosophila innubila reveals lineage-specific patterns of selection in immune genes.
- Hill and Unckless (2020A) Recurrent evolution of two competing haplotypes in an insect DNA virus.
- Hill and Unckless (2020B) Selection and demography shape genomic variation in a ‘Sky Island’ species.
Horizontal spread of transposable elements in Drosophila
Previously the transposable element ‘P-element’ horizontally invaded D. melanogaster, causing the hybrid dysgenesis phenotype, a phenotype where females lacked fully developed or functional ovaries. I identified the spread of P-element to D. simulans and characterized hybrid dysgenesis in this species. More recently I have been using sequencing information of the P-elements in D. melanogaster and simulans, combined with world fruit trade data to characterize the phylogeography of the spread of P-element worldwide. I have also been interested in the rates of horizontal transfer of TEs between species of overlapping ranges, using the sympatric D. pseudoobscura group as a study system. I find rampant horizontal exchange between the species, suggesting that hybrid dysgenesis may not be as catestrophic a phenotype in the wild as in the lab.
- Kofler et al (2015) The recent invasion of natural Drosophila simulans populations by the P-element.
- Hill, Schlotterer & Betancourt (2016) Hybrid dysgenesis in Drosophila simulans associated with a rapid invasion of the P-element.
- Hill & Betancourt (2018) Extensive horizontal exchange of transposable elements in the Drosophila pseudoobscura group.
- Hill (2019) Transposable element dynamics are consistent across the Drosophila phylogeny, despite drastically differing content.
- Hill et al (in prep) The phylogeography of dysgenesis-causing transposable elements in Drosophila melanogaster and simulans.
- Hill et al (in prep) The evolution of the piRNA pathway across the Drosophila phylogeny.
Balancing selection in the Drosophila immune system mediated by rampant gene duplication
While it appears that a majority of immune genes in Drosophila melanogaster are evolving under positive selection, a few genes, such as AMPs, and immune genes in other species, appear to be under balancing selection, likely due to a trade off between the benefit of a resistance allele under infection and its cost when not infected. I’m interested in the population genetics of these genes and the causes of the signatures of balancing selection, specifically if these are driven by duplication events. I am currently using machine learning to identify if AMPs duplicate more than background genes across the Drosophila phylogeny.
- Chapman, Hill and Unckless (2019) Balancing selection drives maintenance of genetic variation in Drosophila antimicrobial peptides.
- Hill & Unckless (2019) A simple deep-learning approach for detecting duplications and deletions in next-generation sequencing data.
- Hill & Unckless (In prep) Rampant duplication drives antimicrobial peptide diversity across the Drosophila phylogeny.
Speciation and genome evolution in the Drosophila dunni subgroup
The Drosophila dunni subgroup is a species group spread across Carribbean islands, with one species per island. The species in this subgroup are recently diverged with differing levels of isolation between species. I am interested in the divergence between two species, D. nigrodunni and D. arawakhana, in which one direction of the cross produces only female offspring and reduces the lifespan of mated females. I suspect divergence in seminal fluid proteins may drive these effects to some degree and so am no investigating genome evolution and seminal fluid protein evolution across this species group.