Program in Ecology (PiE) and Department of Botany, University of Wyoming
Graduate Advisor: Dr. Catherine E. Wagner
Explaining how multiple closely-related species originate and co-occur in hotspots of biological diversity is a long-lasting enigma in evolutionary ecology. Why do some lineages undergo dramatic diversification whereas others do not? Situations where both species-rich and species-poor lineages within a taxonomic group co-occur provide us with natural experiments where we can test why such heterogeneity in diversification rates occurs. One simple hypothesis is that lineages with more restricted dispersal are more prone to form population isolates which subsequently become species; in this scenario, the limiting step to diversification rates are rates of population splitting. Although this is a simple idea that has long been conceptualized in the literature, it has rarely been tested due to limitations associated with collecting spatial population genetic data from whole clades of organisms – the data required to test such a hypothesis. Thankfully, the use of genomic sequencing technologies and computational resources provide us with the novel opportunity to re-evaluate this hypothesis with unprecedented resolution. Specifically, using next generation sequencing technologies, we can assess details of spatial genetic structure within species, and with the same datasets evaluate phylogenetic relationships among species, and using thousands of individuals. Understanding the links between spatial genetic structure and diversification rates represents an emerging frontier in evolutionary ecology, and also provides the potential for important insights into how to best protect the world’s most biodiverse communities.
Although many studies have sought to test for links between traits and diversification rates e.g., relatively few studies have explored the relationship between populationlevel processes and macroevolutionary patterns e.g. In the effort to link population-level processes to speciation, and speciation patterns to diversification, a key goal is better understanding the links between organismal traits and population-level demography (e.g. dispersal rates; population size). Patterns in spatial decay in genetic similarity (known as isolation-by-distance, or IBD) occur because of dispersal limitations leading to greater likelihood of individuals mating with individuals that are close in geographically rather than distant. Dispersal limitation may result from: (1) extrinsic environmental factors affecting animal movement (e.g. dispersal barriers), or extrinsic drivers governing population growth dynamics (e.g. resource availability), and (2) intrinsic organismal traits limiting the probability for dispersal (e.g. traits influencing movement). Studying patterns of spatial decay in genetic similarity in both species-rich and species-poor lineages, and the correlates of these spatial patterns, will help us to identify the drivers underlying hotspots and coldspots in biodiversity.
Share This Page
Fig. 1: Satellite view of Lake Tanganyika, East Africa (A), cichlid diversity in the sand and in the rocky littoral zone (B-C).
Fig. 2: Preliminary data on ß slopes calculated for 4 monotypic genera and 5 non-monotypic taxa from species-rich genera (A). A cladogram depicting relationships among taxa is shown in B. These preliminary data indicate that species from monotypic genera show less population structure than nonmonotypic genera.