# Historical introgression as a driver of diversification of diploid Picris (Compositae) in the Mediterranean Basin

## TL;DR

This study explores how historical hybridization events shaped the evolution of diploid Picris plants in the Mediterranean, contributing to their diversification.

## Contribution

The study provides evidence that historical introgression, rather than adaptive traits, drove diversification in diploid Picris species.

## Key findings

- Phylogenetic analysis identified two major introgression events shaping Picris evolution.
- Introgression events contributed to shifts in life strategy and fruit morphology.
- Hybridization events occurred in the Turkish endemic P. campylocarpa and related lineages.

## Abstract

The Mediterranean Basin is recognized as one of the world's most prominent biodiversity hotspots, where past climatic changes have driven range shifts, secondary contact between populations, and gene exchange. This study investigates the impact of historical introgression on the diversification of diploid members of the genus Picris (Compositae). Using nuclear and plastid genome data obtained through the Hyb‐Seq approach, we assess whether introgression contributed to the evolution of the Mediterranean Picris, potentially giving rise to multiple regional endemics. We also test whether introgression was associated with the transfer of traits such as life strategy and fruit morphology, which are involved in habitat‐specific adaptation. Phylogenetic network analysis revealed two major introgression events that shaped evolutionary trajectories within the genus. The earliest and most complex events involved the Turkish endemic P. campylocarpa, which hybridized with the most recent common ancestor (MRCA) of the P. cyprica–P. pauciflora lineage and with the MRCA of the B1 subclade, comprising the P. hieracioides group and the P. scaberrima–P. strigosa lineage. The latter introgression preceded shifts from iteroparity to semelparity and from heterocarpy to homocarpy, ruling out an adaptive introgression origin for these traits. Nevertheless, all detected historical introgression events contributed to the diversification of diploid Picris taxa.

The remarkable biodiversity of the Mediterranean Basin has developed over extensive geological timescales predominantly through geographical and ecological divergence, frequently associated with polyploidy. Recurrent paleoclimatic and paleogeological oscillations, however, have repeatedly facilitated the formation of contact zones, where hybridization has played a key evolutionary role in driving diversification and speciation, thereby underpinning the exceptional biotic richness within this global biodiversity hotspot.