Polyploidy-driven niche divergence and biogeographic patterns in Bothriochloa Kuntze (Poaceae)

Abstract

Polyploidy is a major evolutionary force that contributes to plant diversification, ecological plasticity, andbiogeographic expansion. In polyploid complexes, genome duplication can promote environmental nichedivergence among cytotypes, facilitating adaptation to distinct climatic conditions. Here, we test the hypothesisthat polyploidization drives ecological niche differentiation and geographic distribution in polyploid cytotypes ofBothriochloa Kuntze in the Americas. Using ecological niche modelling (ENM), PCA-env ordination and nicheoverlap analyses, we evaluated environmental niche shifts between hexaploid (2n = 60) and higher ploidy (2n =120, 2n = 180) cytotypes of five Bothriochloa species. We found a strong association between ploidy level andclimatic niche differentiation. Higher ploidy cytotypes exhibited broader ecological niches than hexaploids andoccupied a wider range of biomes, particularly those characterized by warmer and drier conditions. Nicheoverlap analysis revealed significant ecological divergence between ploidy levels, as evidenced by low values ofSchoener’s D and non-equivalent environmental spaces. Climatic variables, such as water vapour pressure, solarradiation, and temperature range, were key drivers of niche shifts. Our findings support the hypothesis thatpolyploidy facilitates ecological niche divergence, potentially enhancing establishment and diversification.Genome duplication thus emerges as a key mechanism promoting adaptation and biogeographic expansion inresponse to climatic gradients.