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首页> 外文期刊>Forest Ecology and Management >Tree density and population size affect pollen flow and mating patterns in small fragmented forest stands of pedunculate oak ( Quercus robur L.).
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Tree density and population size affect pollen flow and mating patterns in small fragmented forest stands of pedunculate oak ( Quercus robur L.).

机译：树木的密度和种群大小会影响有花梗橡木（Quercus robur L.）的小碎片林中的花粉流动和交配方式。

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In many parts of the world, once large and continuous forests have been replaced by a mosaic of isolated forest fragments embedded in an agricultural or urban landscape matrix. At the same time, stand characteristics such as tree population size and tree density have been strongly modified as a result of anthropogenic activities. Because increased geographical isolation can impede gene flow among forest fragments, and because decreased population size and tree density may reduce the number of local mating partners, this can be expected to lower the opportunity to trees for outcrossing, and to result in increased inbreeding, negatively impacting the viability of fragmented tree populations. In this study, we examined eight isolated stands of the wind-pollinated tree species Q. robur that strongly differed in population size, tree density and spatial isolation. In the centre of each Q. robur stand, adult leaves and seeds were collected in a circular plot, in which we evaluated the diversity and differentiation of the local pollen pool, and examined mating patterns. Most forest stands showed high proportions of out-of-plot pollen flow (range: 0.24-0.77), which were positively correlated with the number and density of adult trees within the forest stands. Despite high outcrossing rates (>0.998), seeds within seed families were stronger related than what could be expected under panmixia, which could be attributed to small but significant levels of correlated paternity (0.018-0.107) and biparental inbreeding (0.025-0.118) within the study plots. Next to increased coancestry coefficients, deviations from random mating also resulted in significant pollen pool differentiation (0.008-0.059) among seed parents. We also found that stand population size and tree density were significantly correlated to the relatedness of the seedlings and the degree of pollen differentiation within the study plots. These results suggest that, in small and isolated low density forest stands, reduced mate availability may decrease local pollen pool diversity, increasing the likelihood of consanguineous mating and pollen pool differentiation in the next generations. We conclude that preserving high levels of pollen flow within and between forest fragments may be more important in wind-pollinated tree species than what was previously thought.
机译：在世界许多地方，曾经被农业或城市景观矩阵中嵌入的孤立森林碎片镶嵌而成的大片和连续森林所取代。同时，由于人为活动，林分特征（例如树木种群大小和树木密度）已被强烈改变。由于增加的地理隔离度可能会阻碍森林碎片之间的基因流动，并且由于减少的种群规模和树木密度可能会减少本地交配伙伴的数量，因此可以预期这会减少树木杂交的机会，并不利于近交繁殖影响零散的树木种群的生存能力。在这项研究中，我们研究了八种孤立的风铃花树种罗伯特罗布斯（Q. robur），它们在种群大小，树木密度和空间隔离方面存在很大差异。在每个罗伯特·罗伯（Q. robur）林分的中心，以圆形图收集成年叶片和种子，在其中我们评估了当地花粉库的多样性和分化，并研究了交配模式。大多数林分显示出高比例的积花粉流（范围：0.24-0.77），这与林分内成年树的数量和密度成正相关。尽管异种交配率高（> 0.998），但种子家族中的种子之间的关联性强于全民混合条件下的预期，这可能归因于内部亲子关系较小（0.018-0.107）和双亲近交（0.025-0.118）的水平很小但很重要研究情节。除了增加coancestry系数，与随机交配的偏离还导致种子亲本之间明显的花粉库分化（0.008-0.059）。我们还发现林分种群大小和树木密度与研究地块内幼苗的相关性和花粉分化程度显着相关。这些结果表明，在小而孤立的低密度林分中，减少的配偶可减少本地花粉池的多样性，增加近代交配和花粉池分化的可能性。我们得出的结论是，在风媒树种中，保持森林碎片内部和森林碎片之间的高水平花粉流动比以前认为的更为重要。

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