Department of Ecology and Evolutionary Biology, University of California Los Angeles, Box 951606, Los Angeles, California 90095-1606 USA.
Am J Bot. 2008 May;95(5):568-76. doi: 10.3732/ajb.2007024.
Epiphytic lichens possess unique life history traits that can have conflicting effects on genetic structure: symbiotic mutualism between a fungus with its algal or cyanobacterial photobiont, association with a host plant, and ability to reproduce sexually and asexually. Our study species, Ramalina menziesii, has small ascospores that can facilitate long-distance gene movement, and it is capable of clonal reproduction. The goals of this study are to test whether different haplotypes were differentially distributed across host plant species, to look for evidence of asexual vs. sexual reproduction, and to assess the local genetic structure of the population. We sampled individuals from multiple trees of three oak species in four lichen subpopulations within a savanna ecosystem. Using DNA sequence data from four fungal nuclear loci, we found no tendency for host specialization. Alleles were randomly distributed across subpopulations. The frequency of multilocus genotypes was consistent with a randomly mating population. Sexual reproduction involving relichenization appeared to be the predominant mode of reproduction of R. menziesii at this study site. We found no significant local genetic structure suggesting widespread gene flow at the local scale. The genetic structure of this lichen is comparable to that of widely distributed epiphytic plants.
附生地衣具有独特的生活史特征，这些特征可能对遗传结构产生冲突影响：真菌与其藻类或蓝细菌共生体之间的共生互惠关系、与宿主植物的联系以及有性和无性繁殖的能力。我们的研究物种，梅氏树花衣，具有可以促进长距离基因流动的小孢子囊，并且能够进行无性繁殖。本研究的目的是检验不同单倍型是否在宿主植物物种之间存在差异分布，寻找有性与无性繁殖的证据，并评估种群的局部遗传结构。我们从萨凡纳生态系统中四个地衣亚群的三种栎属树种的多棵树上取样。使用来自四个真菌核基因座的 DNA 序列数据，我们没有发现宿主特化的趋势。等位基因在亚群中随机分布。多基因座基因型的频率与随机交配的种群一致。涉及再地衣化的有性繁殖似乎是本研究地点梅氏树花衣的主要繁殖方式。我们没有发现明显的局部遗传结构，表明在局部尺度上存在广泛的基因流动。这种地衣的遗传结构与广泛分布的附生植物相似。
