title: Strong reproductive isolation despite occasional hybridization between a widely distributed and a narrow endemic Rhododendron species.
abstract: Reproductive isolation (RI) plays an important role for speciation, but assessing reproductive barriers at all life-cycle stages remains challenging. In plants, most studies addressing the topic have been focusing on herbs with short generation times. The present study attempted to quantify several reproductive barriers between a hybridizing species pair of long-lived woody rhododendrons. Consistent with findings of previous studies, pre-zygotic reproductive barriers contributed more to total RI than post-zygotic reproductive barriers. Especially in the more widespread species geographic isolation was an important barrier, and pollinator constancy contributed exceptionally to RI in both species. Additionally to strong pre-zygotic reproductive barriers, post-zygotic reproductive barriers were considerable, and had asymmetric tendencies favoring one of the species as maternal parent. Overall, despite occasional hybridization, the present study provides evidence for strong RI between R. cyanocarpum and R. delavayi.
authors.affiliation: Key Laboratory for Plant Diversity and Biogeography of East Asia, Kunming Institute of Botany, Chinese Academy of Sciences, Kunming 650201, Yunnan, PR China.
authors.forename: Yong-Peng
authors.initials: YP
authors.lastname: Ma
authors.affiliation: Flower research institute, Yunnan Academy of Agriculture Sciences, Kunming 650201, PR China.
authors.forename: Wei-Jia
authors.initials: WJ
authors.lastname: Xie
authors.affiliation: Key Laboratory for Plant Diversity and Biogeography of East Asia, Kunming Institute of Botany, Chinese Academy of Sciences, Kunming 650201, Yunnan, PR China.
authors.forename: Wei-Bang
authors.initials: WB
authors.lastname: Sun
authors.affiliation: Key Laboratory for Plant Diversity and Biogeography of East Asia, Kunming Institute of Botany, Chinese Academy of Sciences, Kunming 650201, Yunnan, PR China.
authors.forename: Tobias
authors.initials: T
authors.lastname: Marczewski
mesh_terms: D006824:Hybridization, Genetic; D054817:Pollination; D012098:Reproduction; D060047:Reproductive Isolation; D029793:Rhododendron / Q000737:chemistry / Q000235:genetics; D012987:Soil / Q000737:chemistry
chemical_list: D012987:Soil