Phylogenomic Evidence of Fire Regime Changes: The Case of a Resprouting Juniper

Abstract

The onset of the Mediterranean climate, with its characteristic seasonal droughts and increased fire activity, marked a significant shift in the evolution of Mediterranean flora. One trait to adapt to this fire regime shift is the ability to resprout from a lignotuber. We used genotyping-by-sequencing (GBS) data to estimate the origin of lignotuber resprouting in the Iberian Juniperus oxycedrus complex and the period when fires—and the Mediterranean seasonality—became sufficiently frequent and stable to favour such plant adaptations. We then infer the demographic consequences of possessing this trait. Results indicate that resprouting and non-resprouting lineages diverged around 6.23 Ma, aligning with key aridification events (e.g., the Messinian Salinity Crisis) followed by the establishment of the Mediterranean climate. We propose that fire-adaptive traits, such as lignotuber resprouting, can serve as proxies to estimate fire regime shifts; by doing so, we provide new insights into the assembly of the Mediterranean biome.