Components of reproductive isolation between Orchis mascula and O. pauciflora

Studies of the strength and nature of reproductive isolation (RI) between species can greatly contribute to our understanding of speciation. Although the role of RI in speciation is well recognized, there is a dearth of information on the contributions of different barriers between related plant species. Here, we estimated multiple components of RI between two Mediterranean orchid sister species (Orchis mascula and Orchis pauciflora), disentangling the strength and absolute contributions of seven different isolating mechanisms. Our survey includes one prepollination, two postpollination prezygotic (pollen–stigma incompatibility, conspecific pollen precedence), two intrinsic postzygotic (embryo mortality and hybrid sterility) and two extrinsic postzygotic (hybrid habitat differentiation and hybrid pollination) isolating mechanisms. We found strong RI between the investigated species, although none of the barriers were able to completely impede gene flow. Five isolating mechanisms contrib...对物种间生殖隔离（reproductive isolation, RI）的强度与本质开展研究，可极大助力我们对物种形成机制的认知。尽管学界已充分认可RI在物种形成中的作用，但当前仍缺乏近缘植物类群间各类隔离屏障贡献度的相关数据。本研究对两种地中海兰科姊妹物种——雄红门兰（Orchis mascula）与少花红门兰（Orchis pauciflora）间的RI多组分进行了估算，厘清了7种不同隔离机制的作用强度与绝对贡献。本次调查涵盖1种传粉前隔离机制、2种传粉后合子前隔离机制（花粉-柱头不亲和性、同种花粉优先）、2种合子后内在隔离机制（胚胎死亡与杂种不育）以及2种合子后外在隔离机制（杂种生境分化与杂种传粉）。研究发现，所涉物种间存在较强的RI，尽管所有隔离屏障均无法完全阻断基因流。共有5种隔离机制贡献……