Integration of De Novo Chromosome-Level Genome and Population Resequencing of Peganum (Nitrariaceae): A Case Study of Speciation and Evolutionary Trajectories in Arid Central Asia

Abstract

Natural hybridization is a significant driving force in plant evolution and speciation. Understanding the genetic mechanism and dynamic evolutionary trajectories of divergence between species and hybrids remains a central goal in evolutionary biology. Here, we examined the genetic divergence of Peganum and their intermittent and hybrid entities (IHEs) from large-scale sympatric and allopatric regions. We sequenced the genomes of Peganum from the Arid Central Asia (ACA) region and its surrounding areas, discovering that the origin of Peganum could be traced to the Hexi Corridor in eastern Central Asia, where migration led to geographic and environmental isolation, giving rise to new species based on natural selection. Different Peganum species, exhibiting excellent dispersal abilities, migrated to the same regions and underwent hybridization. The descendant species of Peganum inherited and developed adaptive traits from parent species through gene flow and introgression, particularly in DNA repair and wax layer formation, leading to the speciation of the IHEs. This study clarified the transition stages in hybrid speciation and identified the Mixing-Isolation-Mixing cycles (MIM) model as a speciation framework suitable for Peganum, marking the initial identification of this unique evolutionary model in the ACA region.