Hybridization in plants may result in hybrid speciation or introgression and, thus, is now widely understood to be an important mechanism of species diversity on an evolutionary time scale. However, no study has attempted to investigate the genome-wide patterns of hybridization and gene flow among fern species.
In a study published in Molecular Biology and Evolution, researchers from South China Botanical Garden (SCBG) and Xishuangbanna Tropical Botanical Garden (XTBG) tested the hypothesis that Gymnosphaera metteniana (scaly tree fern) originated through hybridization between G. denticulata and G. gigantea.
The researchers combined analyses of cytology via flow cytometry, phylogeny, population genomics, and climatic niches.
They detected substantial introgression of G. denticulate into G. metteniana probably via unreduced gametes. The timing of hybridization and polyploidization likely coincided with the period of intensified East Asian monsoon around the Pliocene and Pleistocene epochs in southern China.
While they demonstrated ecological niche separation between the allotetraploid G. metteniana from its diploid progenitor, G. gigantea, the similar niche observed between G. metteniana and G. denticulata suggested that either some degree of intrinsic genetic isolation or local adaptation may be playing an important role in the evolution of reproductive barriers.
“To our knowledge, our study represents one of the best-documented cases thus far of allopolyploid speciation in ferns”, said a correspondence of the study.
Principal investigator of Macroevolution group
Center for Integrative Conservation, Xishuangbanna Tropical Botanical Garden, Chinese Academy of Sciences, Menglun, Mengla, Yunnan 666303, China