Resolving spatial complexities of hybridization in the context of the gray zone of speciation in North American ratsnakes (Pantherophis obsoletus complex)

Inferring the history of divergence between species in a framework that permits the presence of gene flow has been crucial for characterizing the “gray zone” of speciation, which is the period of time where lineages have diverged but have not yet achieved strict reproductive isolation. However, estimates of both divergence times and rates of gene flow often ignore spatial information, for example when considering the location and width of hybrid zones with respect to changes in environment between lineages. To connect phylogeographic estimates of lineage structure, migration, historical demography, and timing of divergence with hybrid zone dynamics, we used population genomic data from the North American ratsnake complex (Pantherophis obsoletus). We examined the spatial context of diversification by linking migration and timing of divergence to the location and widths of hybrid zones. Artificial neural network approaches were applied to understand how landscape features and past climate...