Researchers from the Xishuangbanna Tropical Botanical Garden (XTBG) of the Chinese Academy of Sciences have uncovered a significant relationship between polyploidy and long-distance dispersal (LDD) in the global species diversification of the Rorippa plant genus. The study, published in Global Ecology and Biogeography, sheds light on the joint roles of polyploidy and LDD in shaping the biogeography of Rorippa, a Brassicaceae genus that originated approximately 7.10 million years ago.
Using nucleotide data from plastid genomes and low-copy nuclear loci, the researchers established well-resolved and dated phylogenies for 58 Rorippa species. Their analysis revealed a synergistic relationship between polyploidy and LDD, providing insights into their combined impact on global species diversification.
The study identified that LDD played a crucial role in the amphitropical disjunction of Rorippa, with polyploids demonstrating higher dispersal rates compared to diploids. Transoceanic speciation events were observed, with 21 polyploids and five diploids identified as products of such events. Additionally, the study found that polyploidy, following LDD, was more common than polyploidy preceding LDD.
Plastid biogeography analysis suggested that frequent LDD shaped the amphitropical disjunction of Rorippa species, with polyploidy playing a significant role during LDD. The overall global biogeography indicated that polyploidy may have mediated the success of LDD in the Southern Hemisphere.
The study establishes that polyploidy is not only a driver but also a responder to LDD in Rorippa, emphasizing a synergistic relationship between the two processes. The findings provide a framework for understanding the biogeographical consequences of polyploidization and the joint roles of polyploidy and LDD in shaping biodiversity distribution. Xing Yaowu of XTBG highlighted the significance of the results in comprehending plant species adaptation and spread to new geographic areas, offering valuable insights for the conservation and management of Rorippa.