Formation and establishment of neopolyploids from sterile hybrids in Drosera in a disturbed environment
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Formation and establishment of neopolyploids from sterile hybrids in Drosera in a disturbed environment Yuri Hoyo & Yoichiro Hoshino & Shiro Tsuyuzaki
Received: 29 November 2019 / Revised: 27 August 2020 / Accepted: 16 September 2020 # Institute of Botany, Czech Academy of Sciences 2020
Abstract Neopolyploid species have been used as model plants to elucidate the consequences of hybridization and polyploidy. Two Drosera species, D. anglica Hudson (2n = 4x = 40) and D. rotundifolia L. (2n = 2x = 20), and the hybrid D. ×obovata Mert. et Koch (2n = 3x = 30), which results from their crossing, have been reported from Hokkaido Island, northern Japan. Recently, we discovered unexpected higher ploidy levels within the population of these Drosera from a post-mined peatland, in Sarobetsu mire of Hokkaido. The ploidy levels were determined by flow cytometry. Polyploids were tagged and monitored at the site for three years. The morphological characteristics of the neopolyploid leaves and flowers were determined and compared to D. anglica, D. rotundifolia and D. ×obovata. Seeds collected from hexaploids were incubated in a laboratory to verify their viability. Hexaploids occurred in the field over the three years of monitoring and produced a few flowers and viable seeds; however, octoploids were extinct in the second year. The leaf
Y. Hoyo (*) Graduate School of Environmental Science, Hokkaido University, Sapporo 060-0810, Japan e-mail: [email protected] Y. Hoshino Field Science Center for Northern Biosphere, Hokkaido University, Sapporo 060-0811, Japan S. Tsuyuzaki Graduate School of Environmental Earth Science, Hokkaido University, Sapporo 060-0810, Japan
shape quantified by the blade length to blade width ratio showed that the ratios of hexaploids were intermediate between D. ×obovata and D. rotundifolia, suggesting that the origin of hexaploids was likely to originate from the triploid D. ×obovata. Polyploidy may occur in disturbed habitats more commonly than previously thought. Keywords Allopolyploidy . Chromosome-doubling . Drosera . Hybrid . Polyploidization . Speciation
Introduction Polyploidization often promotes plant speciation (Rieseberg and Wiltis 2007). All extent angiosperms have experienced multiple polyploidizations in their phylogenetic history that have contributed to the improvement of their genetic and morphological diversities (Soltis and Soltis 2009). Neopolyploid species are used as model plants to elucidate the mechanisms of evolution (Mandáková et al. 2013; Čertner et al. 2017). Drosera (Droseraceae) is a polytypic genus of worldwide distribution, including nearly 150 species, characterized by variation in chromosome number and a high incidence of new polyploid species (Juniper et al. 1989; Rivadavia et al. 2003). The centre of Drosera diversity appears to be Australia, where over eighty species are found and the polymorphisms of chromosome numbers and karyotypes are reported (Sheikh et al. 1995; Hoshi and Kondo 1998). Most of the northern hemisphere species, which belong to section Drosera (Sei
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