title: Reproductive isolation is mediated by pollen incompatibility in sympatric populations of two Arnebia species.
abstract: To explore uncertain aspects of the processes that maintain species boundaries, we evaluated contributions of pre- and postpollination reproductive isolation mechanisms in sympatric populations of Arnebia guttata and A. szechenyi. For this, we investigated their phylogenetic relationships, traits, microenvironments, pollinator visits, action of natural selection on floral traits, and the outcome of hand pollination between the two species. Phylogenetic analysis indicates that A. szechenyi is a derived species that could be closely related to A. guttata, and both could be diploid species. Arnebia guttata flowers have larger parts than A. szechenyi flowers, but smaller nectar guides. Soil supporting A. szechenyi had higher water contents than soil supporting neighboring populations of A. guttata (in accordance with their geographical distributions). The pollinators shared by the two species preferred A. szechenyi flowers, but interspecific visitations were frequent. We found evidence of conflicting selection pressures on floral tube length, flower diameter and nectar guide size mediated via male fitness, and on flower diameter and floral tube diameter via female fitness. Hand-pollination experiments indicate complete pollen incompatibility between the two species. Our results suggest that postpollination prezygotic mechanisms are largely responsible for reproductive isolation of sympatric populations of the two Arnebia species.
authors.affiliation: Key Laboratory for Plant Diversity and Biogeography of East Asia Kunming Institute of Botany Chinese Academy of Sciences Kunming 650201 China; Plant Germplasm and Genomics Center the Germplasm Bank of Wild Species Kunming Institute of Botany Chinese Academy of Sciences Kunming 650201 China; Institute of Tibetan Plateau Research at Kunming Kunming Institute of Botany Chinese Academy of Sciences Kunming 650201 China.
authors.forename: Lin-Lin
authors.initials: LL
authors.lastname: Wang
authors.affiliation: College of Life Sciences Henan Normal University Xinxiang 453007 Henan China.
authors.forename: Chan
authors.initials: C
authors.lastname: Zhang
authors.affiliation: Key Laboratory for Plant Diversity and Biogeography of East Asia Kunming Institute of Botany Chinese Academy of Sciences Kunming 650201 China; Key Laboratory of Biodiversity Conservation in Southwest China of State Forestry Administration Southwest Forestry University Kunming 650224 Yunnan China.
authors.forename: Bin
authors.initials: B
authors.lastname: Tian
authors.affiliation: Key Laboratory for Plant Diversity and Biogeography of East Asia Kunming Institute of Botany Chinese Academy of Sciences Kunming 650201 China; Plant Germplasm and Genomics Center the Germplasm Bank of Wild Species Kunming Institute of Botany Chinese Academy of Sciences Kunming 650201 China; Institute of Tibetan Plateau Research at Kunming Kunming Institute of Botany Chinese Academy of Sciences Kunming 650201 China.
authors.forename: Xu-Dong
authors.initials: XD
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 China.
authors.forename: Wen
authors.initials: W
authors.lastname: Guo
authors.affiliation: College of Agriculture and Biotechnology Hexi University Zhangye 734000 Gansu China.
authors.forename: Ting-Feng
authors.initials: TF
authors.lastname: Zhang
authors.affiliation: Key Laboratory for Plant Diversity and Biogeography of East Asia Kunming Institute of Botany Chinese Academy of Sciences Kunming 650201 China; Plant Germplasm and Genomics Center the Germplasm Bank of Wild Species Kunming Institute of Botany Chinese Academy of Sciences Kunming 650201 China; Institute of Tibetan Plateau Research at Kunming Kunming Institute of Botany Chinese Academy of Sciences Kunming 650201 China.
authors.forename: Yong-Ping
authors.initials: YP
authors.lastname: Yang
authors.affiliation: Key Laboratory for Plant Diversity and Biogeography of East Asia Kunming Institute of Botany Chinese Academy of Sciences Kunming 650201 China; Plant Germplasm and Genomics Center the Germplasm Bank of Wild Species Kunming Institute of Botany Chinese Academy of Sciences Kunming 650201 China; Institute of Tibetan Plateau Research at Kunming Kunming Institute of Botany Chinese Academy of Sciences Kunming 650201 China.
authors.forename: Yuan-Wen
authors.initials: YW
authors.lastname: Duan
keywords: Floral traits; natural selection; pollen export; pollinator preference; seed set
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