Data from: Integrating phylogeography and paleoecology to investigate the origin and dynamics of hybrid zones: insights from two widespread North American firs

Studying extent and direction of cytoplasmic introgression is useful to unravel hybrid zone dynamics between interbreeding species. The main objective of this study was to characterize the extent of cytoplasmic introgression in the Abies lasiocarpa × Abies balsamea species complex using markers from the mitochondrial (mtDNA) and chloroplast (cpDNA) genomes. Hybrid zone dynamics since postglacial colonization was inferred by assessing the concordance between current and historical locations of the hybrid zone using genetic and paleoecological data. Interspecific gene flow was higher for cpDNA than mtDNA markers and the geographic distribution of mitotypes was thus more congruent with species distributions than chlorotypes. This genetic signature was contrary to expectations under a moving hybrid zone scenario, as well as empirical observations in conifers. Genetic evidence for a stable hybrid zone was corroborated by the colonization chronology derived from published fossil data. While cpDNA interspecific gene flow seemed primarily driven by westerly winds, non-neutral factors may play a role in maintaining a complex yet stable hybrid zone.