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RESEARCH PRODUCT

The plasticity of breeding system in arid-adapted Zygophylloideae

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Abstract The assurance of reproductive success is an important challenge for arid-adapted plants. Self-compatibility is suggested as a mechanism to compensate for the inadequate breeding opportunities in extreme environments. Zygophylloideae is an arid-adapted subfamily which has successfully radiated in different ranges of arid habitats. In order to study the significance of selfing for the reproductive success of the Zygophylloideae, we calculated pollen ovule ratios (P/O) and conducted bagging experiments for autogamy and xenogamy in eleven representative members of Zygophylloideae and three species of the sister subfamilies Tribuloideae and Larreoideae. Our results revealed an extremely high P/O in Zygophylloideae with significant differences between studied species. Control seed set and the seed set produced in autogamy and xenogamy experiments varied in different species. We used both P/O and seed set to estimate the breeding system. Our results indicated that the Zygophylloideae are all self-compatible with different degrees of selfing ranging from obligate autogamy in Augea, to facultative autogamy in Tetraena species, Fagonia and Zygophyllum atriplicoides, and further to facultative xenogamy in Roepera species and Zygophyllum fabago. Interestingly, the degree of selfing within South African species is associated with the aridity level of related habitats.