What makes two perfectly adapted populations stop being able to interbreed? I tend to approach this question by looking at the interactions between genes, and asking how the landscape of these interactions impacts the fate of evolving populations. I think this question is particularly exciting, since many parallels outside of biology exist (e.g. languages, branches of software, legal systems, etc.). Is the break-down of hybrid fitness observed in natural populations a general outcome for any two systems that diverge, or are some properties unique to biology?

While I'm intersted in the evolution of genome organization broadly, I think one of the most dynamic elements of many genomes is the sex chromosomes. Much of our theory and knowledge of sex chromosomes has been based on the rather old and slow to change systems in mammals and birds. However, research in the last few decades has demonstrated that these taxa represent a drastically different view of sex chromosomes than do many fish, amphibians and insects. However, time and time again studies find that these are unique elements when it comes to their role in speciation, introgression, development and many other biological processes. What are the drivers of the evolution of sex chromosomes and their maintenance? What determines the eventual degredation or turnover of these chromosomes?

One of the joys of being a population geneticist in our times is that many parameters that simply had to be assumed are now beginning to be known. On the basic end this means we know the number of genes, mutation rates of those genes, and something about the effective population size of different species. On the more complex end of the scale, we are beginning to truly measure epistatic interactions among vast numbers of mutations, computational methods allow us to get a good idea of the demographic changes in and between species and the selective forces that shape our genome are being measured. This presents a great opportunity for population geneticists to both participate in the analysis of genomic datasets to help infer these previously unknowable parameters, but also to test hypotheses that previously were intractible. Do genes that interact, for instance, end up more closely linked in the genome? Are the epistatic interactions observed in real data sufficient to explain rates of speciation? Is introgression common only between recent species, or is it something that happens even between highly diverged groups? Below is some introgression data (just plants) from a recent meta-analysis the Matute Lab and I performed. There is a large degree of variation in the amount of genome showing evidence for introgression (roughly proportional to Patterson's D) and genetic distance (here measured as Jukes-Cantor), and some of this variation seems to be taxon specific (you can toggle which orders are displayed by clicking them in the legend).

I have recently participated in an NIH T32 training grant for Medical Mycology and Molecular Pathogenesis. This program allowed me to apply many of the genomic techniques I have learned to something more practical - examining the evolutionary history of pathogenic fungi. These fungi are a group of organisms that have historically posed danger primarily to the global south and as a result have received very little attention in science. As part of the training program, I am helping the Matute lab look into species boundaries among Histoplasma species as well as examining the evolutionary relationships between different strains, the evolution of structural variation in these organisms and examining how reference bias impacts evolutionary inference in these (often highly structurally variable) species.