Principles of phylogeography and landscape genetics

Hello, my name's Ryan Garrick. I'm at the University of Mississippi and today I'm going to talk about two of my favorite topics, phylogeography and landscape genetics, which are actually quite closely related to one another. I'll try and point out some of, not only the similarities but also the differences between them.

I'll start with phylogeography. This is a sub-discipline that takes a view of a relatively deeper timescale and broader geographic scale than landscape genetics. It makes sense to start with the big picture.

This is a table summarizing some of the features of the sub-discipline of phylogeography as initially defined by Avise and colleagues many years ago. I think that some of these characteristics are really useful when we make a comparison between phylogeography and landscape genetics. I'll just highlight a few of them. First of all, the main goal of phylogeography is typically to understand and reconstruct long-term population history. Often the timescale of interests can be quite deep, certainly, plus the same age, perhaps earlier, such that we're reconstructing events that are unobservable to humans. So we're using inferences to determine what happens to generate the present-day patterns that we see. The spatial scale of analysis is often range-wide for the focal species. Some of the common types of interests in phylogeographic studies include understanding past events, whether they be range expansion, contraction, lineage splitting, or fusion events that impacted the present-day distribution of genetic diversity, but also understanding recurrence population processes, such as gene flow, for example. The primary data type that is used for phylogeographic analyses really includes geo-referenced DNA-sequence haplotype data. I've noted here that recently single nucleotide polymorphism data are also increasingly being used, but for the purposes today, I'll just assume that the underlying data are the haplotype data. There are non-genetic data that can complement phylogeographic analyses. These include data geological events, perhaps dated fossils and certainly, paleoclimatic or ecological niche modeling projected back into the past. The questions addressed are often those of basic research. Evolutionary questions about how species arise, and what kinds of events have shaped the spatial distribution of genetic diversity within species today.