植物已经进化出各种策略来避免近亲繁殖,但是许多植物显示的大量开花使它们容易受到植物内花粉运动和自花授粉的影响。槲寄生通常在多个空间尺度上聚集。他们的鸟类授粉者经常拜访同一个体和同一宿主树上的其他花朵。我们假设雌雄同体的槲寄生具有减少或防止自交的自交不亲和机制。无论是它们的空间分布,受宿主特异性的影响,主机分布,以及种子传播者的行为,对其交配系统和种群遗传结构的影响尚不清楚。我们使用微卫星标记和后代阵列研究了交配系统和空间分布如何影响中国西南部寄主-多面手槲寄生五味子的四个种群的遗传结构。我们还对一个种群中四个寄主树的166个槲寄生之间的精细尺度空间遗传结构进行了表征。感染的患病率和强度在宿主物种之间似乎都有所不同,强烈影响聚集程度。宿主树的大小对感染强度有很大影响。令人惊讶的是,人工授粉实验表明,五味子是自相容的,但是遗传分析表明,所有四个种群的异交率都高于预期(MLTRtm0.83-1.20,贝叶斯tm0.772-0.952)。空间遗传结构与寄主树之间的距离有关,但在较短的尺度上(在寄主内)无关。我们的结果表明,鸟类授粉的组合,鸟类介导的种子传播,和后扩散过程导致异交,并在双亲近亲繁殖的存在下保持相对较高的多样性,尽管非常高的局部密度和可能的自相容性。
Plants have evolved various strategies to avoid inbreeding, but the mass flowering displayed by many plants predisposes them to within-plant pollen movements and self-pollination. Mistletoes often aggregate at multiple spatial scales. Their bird pollinators often visit several flowers of the same individual and of others on the same host tree. We hypothesized that hermaphroditic mistletoes have self-incompatibility mechanisms that reduce or prevent selfing. Whether their spatial distribution, affected by host specificity, host distribution, and the behaviour of seed dispersers, influences their mating system and population genetic structure remains unclear. We studied how mating system and spatial distribution affect genetic structure in four populations of the host-generalist mistletoe Dendrophthoe pentandra in southwestern
China using microsatellite markers and progeny arrays. We also characterized the fine-scale spatial genetic structure among 166 mistletoes from four host trees in one population. Prevalence and intensity of infection both appeared to vary among host species, strongly affecting the degree of aggregation. Host tree size had a strong effect on infection intensity. Surprisingly, manual pollination experiments indicated that D. pentandra is self-compatible, but genetic analyses revealed that outcrossing rates were higher than expected in all four populations (MLTR tm 0.83-1.20, Bayesian tm 0.772-0.952). Spatial genetic structure was associated with distance between host trees but not at shorter scales (within hosts). Our results demonstrate that the combination of bird pollination, bird-mediated seed dispersal, and post-dispersal processes result in outcrossing and maintain relatively high diversity in the presence of biparental inbreeding, despite very high local densities and possible self-compatibility.