The Roles of Life History and Mating System in Speciation: Genomic Evidence From the Incarvillea sinensis Complex

Area of Science:

• Plant evolutionary biology
• Speciation mechanisms
• Population genomics

Background:

• Understanding the sequence of life-history and mating-system transitions is crucial for plant speciation.
• The Incarvillea sinensis complex offers a model system with annual selfing and perennial outcrossing populations.

Purpose of the Study:

• To investigate the temporal order and interplay of life-history and mating-system evolution in the Incarvillea sinensis complex.
• To determine the drivers and genomic consequences of these transitions.

Main Methods:

• Crossing experiments to assess reproductive isolation.
• Population genomic analyses using SNP and chloroplast sequencing.
• De novo genome assemblies for annual and perennial individuals.

Main Results:

• Complete post-zygotic isolation between annual and perennial lineages.
• Strong genetic divergence between life histories with no contemporary gene flow.
• Annuals showed reduced genetic diversity, elevated differentiation, and more chromosomal rearrangements compared to perennials.
• Life-history divergence occurred in the early Pleistocene, while mating-system shift to selfing was a more recent event in the late Pleistocene.

Conclusions:

• Life-history transition (annuality) likely preceded mating-system transition (selfing).
• Adaptation to arid environments may have driven the evolution of annuality, initiating speciation.
• Subsequent evolution of selfing further promoted reproductive isolation and genomic differentiation, completing speciation.