Heteroploidy hybridization and apomixis facilitate the origin of a new Elatostema species: Insights from evidence of phylogenomics, flow cytometry, cytology and morphology.

Apomixis can confer fertility upon spontaneous hybrids and allopolyploids, both of which have played a pivotal role in the evolutionary trajectory and diversification of flowering plants. We hypothesized that an unusual morphotype of represents a viable hybrid species between and , as opposed to a sterile F1 hybrid. To test this, we employed phylogenomic, flow cytometry (FC), cytological, and morphological analyses. A two‐step phylogenomic approach was used. Genome skimming was performed on one population, three populations of each parent ( , ), and ten and one species. Population genetic analyses were then conducted using RAD sequencing data from the type population of hybrid and parent species. Phylogenomic analyses using genome skimming and RAD sequencing data consistently supported a hybrid origin, placing close to or nested within and distant from . Chromosome counts revealed pentaploid, triploid, and tetraploid ploidy levels in , , and , respectively. FC suggested apomixis in and , while exhibited sexual reproduction. Morphological studies indicated that shares traits from both parents. Our findings demonstrate a novel reproductively viable hybrid species in , likely originated through a natural hybridization event involving heteroploidy, coupled with the inheritance of an apomictic reproductive pathway from its maternal parent. These results provide compelling evidence that hybridization and apomixis have played pivotal roles in driving reticulate evolution and promoting diversification within the .

Project(s)

Priority 4: Accelerated Taxonomy

Funder

Funder name	Awards
Guangxi Natural Science Foundation Program, China	(2022GXNSFAA035440)
Light of West China Program, Chinese Academic of Sciences, China	([2020]82)
National Natural Science Foundation of China, China	(32160082) - (32360297)
Guangxi Key Laboratory of Plant Conservation and Restoration Ecology in Karst Terrain, China	(22‐035‐26)
Science Research Foundation, Guangxi Institute of Botany, China	(Guizhiye 23004)
Basic Research Fund, Guangxi Academy of Sciences, China	(CQZ‐C‐1901)