2025 Theses Doctoral

Phylogeography, diversification, and conservation of temperate mountain flora

Meek, Jared Bryant

Over the past two decades, multiple hypotheses and datasets have emerged to describe the impacts of mountain uplift, Quaternary glacial cycles, and climatic transitions on plant diversification in mountain systems across the world. While many studies have documented these large-scale dynamics for species in mountains generally, few have used population genomics to identify specific geographic barriers and quantify their impacts on population divergence and gene flow. My research uses phylogeographic and population genomic approaches to describe how these evolutionary processes and landscape features have influenced each other to drive diversification across two temperate mountain regions - the Hengduan Mountains of China and the North American Cordillera.

Chapter 1 focuses on the phylogeographic histories of twelve widespread Pedicularis species in the Hengduan Mountains Region (HMR). It is common to find many species of Pedicularis flowering in sympatry in this region, and an outstanding question is whether such species have experienced parallel phylogeographic histories as their populations have diverged across the HMR. This chapter outlines the phylogenetic and population genetic approaches I used to determine the population structure and migration potential for each species, highlighting areas of the landscape that appear to function as barriers to gene flow.

In Chapter 2, I characterize population structure and historical patterns of gene flow within the Pedicularis cranolopha species complex. Additionally, I use a dataset of historical-contemporary samples to develop a novel temporal genomics framework that allows us to test whether gene flow has increased in recent time due to human impacts across the HMR landscape. Since the Pedicularis cranolopha genome was recently assembled, I was able to use whole-genome sequencing (WGS) to assemble a more robust dataset for investigating genomic changes over time.

Chapter 3 begins to clarify the phylogenetic relationships of Delphinium sect. Diedropetala across the North American Cordillera. This clade includes 60 species which have rapidly diversified across mountain regions of western North America in the last 3-5 million years. In collaboration with researchers from the USDA Agricultural Research Service, I used RADseq data from 34 species to infer the first phylogeny of Delphinium species endemic to North America based on genome-wide data.