Combined observational and experimental data provide limited support for facilitation in lichens

It is increasingly recognized that facilitative interactions can shape communities. One of the mechanisms through which facilitation may operate is when one species facilitates the colonization of another through the exchange of shared symbionts. Lichens are symbiotic associations composed of a mycobiont (lichenised-fungus) and one or two photobionts (algae or cyanobacteria). Different lichen species may have overlapping specificity for photobionts, creating the possibility that facilitation drives lichen community assembly. To investigate whether facilitation occurs in lichens, we combined an observational study (a) with a manipulative field experiment (b). For (a), we quantified the effect of local patch conditions, facilitation and the size of the surrounding metapopulation on colonizations of an epixylic lichen species (Cladonia botrytes) in an area of managed boreal forest. This was done by twice surveying lichens on 293 stumps, located in stands of three age classes. For (b), we t...学界日益达成共识：种间促进作用可塑造群落结构。促进作用可通过多种机制发挥作用，其中一种核心路径为：某一物种通过交换共享共生体（symbionts），促进另一物种的定植。地衣是一类共生联合体，由真菌共生体（mycobiont，即地衣型真菌lichenised-fungus）与一种或两种光合共生体（photobionts，包括藻类algae或蓝细菌cyanobacteria）组成。不同地衣物种对光合共生体的宿主专一性可能存在重叠，这为促进作用驱动地衣群落组装提供了理论可能。为探明地衣生态系统中是否存在促进作用，本研究将观测研究（a）与控制性野外实验（b）相结合。针对观测研究（a），我们量化了局域斑块条件、促进作用及周围异质种群（metapopulation）规模，对经营型北方针叶林区域内木生地衣（epixylic lichen）物种葡萄石蕊（Cladonia botrytes）定植过程的影响；该研究通过两次调查完成，对分布于三个林龄级林分中的293个树桩上的地衣开展了两次普查。针对控制性野外实验（b），我们……