Área de Biodiversidad y Conservación, Departamento de Biología y Geología, Universidad Rey Juan Carlos, E-28933 Móstoles, Spain.
Fungal Biol. 2011 Dec;115(12):1270-8. doi: 10.1016/j.funbio.2011.09.003. Epub 2011 Sep 23.
Persistence and abundance of species is determined by habitat availability and the ability to disperse and colonize habitats at contrasting spatial scales. Favourable habitat fragments are also heterogeneous in quality, providing differing opportunities for establishment and affecting the population dynamics of a species. Based on these principles, we suggest that the presence and abundance of epiphytes may reflect their dispersal ability, which is primarily determined by the spatial structure of host trees, but also by host quality. To our knowledge there has been no explicit test of the importance of host tree spatial pattern for epiphytes in Mediterranean forests. We hypothesized that performance and host occupancy in a favourable habitat depend on the spatial pattern of host trees, because this pattern affects the dispersal ability of each epiphyte and it also determines the availability of suitable sites for establishment. We tested this hypothesis using new point pattern analysis tools and generalized linear mixed models to investigate the spatial distribution and performance of the epiphytic lichen Lobaria pulmonaria, which inhabits two types of host trees (beeches and Iberian oaks). We tested the effects on L. pulmonaria distribution of tree size, spatial configuration, and host tree identity. We built a model including tree size, stand structure, and several neighbourhood predictors to understand the effect of host tree on L. pulmonaria. We also investigated the relative importance of spatial patterning on the presence and abundance of the species, independently of the host tree configuration. L. pulmonaria distribution was highly dependent on habitat quality for successful establishment, i.e., tree species identity, tree diameter, and several forest stand structure surrogates. For beech trees, tree diameter was the main factor influencing presence and cover of the lichen, although larger lichen-colonized trees were located close to focal trees, i.e., young trees. However, oak diameter was not an important factor, suggesting that bark roughness at all diameters favoured lichen establishment. Our results indicate that L. pulmonaria dispersal is not spatially restricted, but it is dependent on habitat quality. Furthermore, new spatial analysis tools suggested that L. pulmonaria cover exhibits a distinct pattern, although the spatial pattern of tree position and size was random.
物种的持久性和丰富度取决于栖息地的可利用性以及在不同空间尺度上扩散和殖民栖息地的能力。有利的栖息地片段在质量上也是异质的，为建立提供了不同的机会，并影响了物种的种群动态。基于这些原则，我们认为附生植物的存在和丰度可能反映了它们的扩散能力，而扩散能力主要取决于宿主树的空间结构，但也取决于宿主的质量。据我们所知，目前还没有对地中海森林中附生植物的宿主树空间格局对其重要性的明确测试。我们假设，在有利的栖息地中，性能和宿主占有率取决于宿主树的空间格局，因为这一格局影响了每个附生植物的扩散能力，也决定了适合建立的地点的可用性。我们使用新的点格局分析工具和广义线性混合模型来检验这一假设，以研究栖息在两种宿主树（山毛榉和伊比利亚栎）上的附生地衣肺衣的空间分布和性能。我们测试了树的大小、空间配置和宿主树的身份对肺衣分布的影响。我们建立了一个包括树的大小、林分结构和几个邻域预测因子的模型，以了解宿主树对肺衣的影响。我们还研究了宿主树配置之外，空间格局对物种存在和丰度的相对重要性。肺衣的分布高度依赖于成功建立的栖息地质量，即树种身份、树径和几个林分结构的替代物。对于山毛榉树，树径是影响地衣存在和覆盖的主要因素，尽管较大的地衣定植树位于焦点树（即幼树）附近。然而，橡树的直径不是一个重要因素，这表明在所有直径上树皮的粗糙度都有利于地衣的建立。我们的结果表明，肺衣的扩散不受空间限制，但依赖于栖息地质量。此外，新的空间分析工具表明，尽管树的位置和大小的空间模式是随机的，但肺衣的覆盖具有明显的模式。
