Speciation genomics in petunias

Closely related Petunia species have evolved highly specialized flowers that attract hawkmoths, hummingbirds, or bees as pollinators. Adaptation to contrasting pollinator preferences involved coordinated changes in flower color, scent composition, nectar volume, and morphology. In my research I aim to understand how these evolutionary transitions affect genome evolution and barriers to genetic introgression by combining comparative and population genomic approaches.

The role of genomic structural variation for adaptation

Genomes can be highly flexible and evolve based on processes that duplicate, remove, or rearrange genetic elements within or among chromosomes. The resulting genomic structural variation can be subject to selection and particular genome architectures might spread because they are beneficial for adaptation. I use a combination of comparative genomics and statistics to investigate whether genome architecture has evolved in a non-random way during adaptation to heterogeneous environments. I apply my work to sticklebacks and test whether genome structural changes may have facilitated their repeated and parallel transitions from marine to freshwater habitats.

Adaptation and speciation in stick insects

Californian stick insects of the genus Timema live and feed on various host plants, with several Timema species showing parallel adaptation to multiple hosts. I use population genomics to study the genetic and environmental processes contributing to local adaptation in these insects and that might be important for population differentiation with gene flow. I largely focus on one species, T. cristinae, which has adapted to different host plants and additionally exhibits a color polymorphism conferring crypsis on different plant parts within hosts (i.e., brown or green morphs cryptic on stems or leaves). I am interested in the evolution and the genetic architecture of this polymorphism, which is maintained in full sympatry by balancing selection.

Hybrid zone simulations

I use computer simulations to study the genomic outcomes of hybridization and admixture. In particular, I am interested in the efficiency of different genetic architectures of reproductive isolation in maintaining species differences in secondary contact, and their effects on introgression and gene flow between species. Together with Alex Buerkle, I worked on the software dfuse that can simulate genomic outcomes of hybridization with different genetic architectures of fitness.

Poplar hybrid zones

I studied the genetics of reproductive isolation and species differences in replicate hybrid zones of European aspen (Populus tremula) and white poplar (P. alba) during my doctoral dissertation. My work revealed that geographically distinct Populus hybrid zones show very similar patterns of genetic ancestry and introgression, indicating a strong role of genetically based reproductive barriers. By jointly inferring genetic ancestry and paternity from genomic data, we could show that postzygotic selection acting on recombinant seedlings contributes substantially to the maintenance of species barriers between these hybridizing, wind-pollinated forest trees.