Werth Silke, Wagner Helene H, Gugerli Felix, Holderegger Rolf, Csencsics Daniela, Kalwij Jesse M, Scheidegger Christoph
Section Ecological Genetics, WSL Swiss Federal Research Institute, 8903 Birmensdorf, Switzerland.
Ecology. 2006 Aug;87(8):2037-46. doi: 10.1890/0012-9658(2006)87[2037:qdaeli]2.0.co;2.
Dispersal is a process critical for the dynamics and persistence of metapopulations, but it is difficult to quantify. It has been suggested that the old-forest lichen Lobaria pulmonaria is limited by insufficient dispersal ability. We analyzed 240 DNA extracts derived from snow samples by a L. pulmonaria-specific real-time PCR (polymerase chain reaction) assay of the ITS (internal transcribed spacer) region allowing for the discrimination among propagules originating from a single, isolated source tree or propagules originating from other locations. Samples that were detected as positives by real-time PCR were additionally genotyped for five L. pulmonaria microsatellite loci. Both molecular approaches demonstrated substantial dispersal from other than local sources. In a landscape approach, we additionally analyzed 240 snow samples with real-time PCR of ITS and detected propagules not only in forests where L. pulmonaria was present, but also in large unforested pasture areas and in forest patches where L. pulmonaria was not found. Monitoring of soredia of L. pulmonaria transplanted to maple bark after two vegetation periods showed high variance in growth among forest stands, but no significant differences among different transplantation treatments. Hence, it is probably not dispersal limitation that hinders colonization in the old-forest lichen L. pulmonaria, but ecological constraints at the stand level that can result in establishment limitation. Our study exemplifies that care has to be taken to adequately separate the effects of dispersal limitation from a limitation of establishment.
扩散是一个对于集合种群的动态变化和持续性至关重要的过程，但难以进行量化。有人提出，老龄森林地衣肺衣受到扩散能力不足的限制。我们通过对ITS（内转录间隔区）区域进行肺衣特异性实时PCR（聚合酶链反应）分析，对从雪样中提取的240份DNA进行了分析，从而能够区分源自单一孤立源树的繁殖体和源自其他地点的繁殖体。通过实时PCR检测为阳性的样本，还针对五个肺衣微卫星位点进行了基因分型。两种分子方法都表明存在来自本地以外来源的大量扩散。在景观层面的分析中，我们还通过ITS实时PCR对240份雪样进行了分析，不仅在有肺衣的森林中检测到了繁殖体，在大片未造林的牧场地区以及未发现肺衣的森林斑块中也检测到了繁殖体。对移植到枫树皮上的肺衣粉芽在两个生长季节后的监测表明，不同林分间生长差异很大，但不同移植处理之间没有显著差异。因此，可能不是扩散限制阻碍了老龄森林地衣肺衣的定殖，而是林分层面的生态限制导致了定殖限制。我们的研究表明，必须注意充分区分扩散限制的影响和定殖限制。
