DISSERTATION RESEARCH: Chromosome inversions and reproductive isolation in an avian hybrid zone

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Scientists' understanding of the way in which two species arise from a common ancestor has greatly improved since the time of Darwin. We now know that the most common way species form is when different populations become geographically separated from each other and begin to genetically diverge. We also know that this process can take millions of years. But at any time, during the process of splitting, populations may come back into contact and form a narrow zone of contact where individuals from one group mate with individuals from the other group (a hybrid zone). While hybridization generally leads to a slowdown in the rate at which new species form because their genomes are no longer separate, several mechanisms have been identified whereby hybridization can actually promote divergence. This project focuses on the evolution of chromosome inversions, rearrangements to the structure of the genome that act as genetic barriers between young species that share some gene exchange in narrow hybrid zones. This information is critical to understanding the natural consequences of geographic divergence, periodic gene exchange, speciation, and the resulting biodiversity that is present on Earth. Education-related public outreach efforts at the Field Museum of Natural History, where the research takes place, will involve Chicago area high school and undergraduate students.These researchers study a hybrid zone between subspecies of the long-tailed finch (Poephila acuticauda). Subspecies differ in beak color (yellow vs. red) and hybridize across a narrow contact zone in northern Australia. Genetic differences between subspecies are largely restricted to one chromosome. Several large chromosome inversions are on the same chromosome. The researchers will examine the genomes of individual birds from across the hybrid zone to identify the genes encoding a reproductive isolating trait: beak color.