Data from: Genetic inference of epiphytic orchid colonization; it may only take one

Colonization of vacant habitat is a fundamental ecological process that affects the ability of species to persist and undergo range modifications in continually shifting landscapes. Thus, understanding factors that affect and limit colonization has important ecological and conservation implications. Epiphytic orchids are increasingly threatened by various factors, including anthropogenic habitat disturbance. As cleared areas (e.g. pastures) are recolonized by suitable host trees, the establishment and genetic composition of epiphytic orchid populations are likely a function of their colonization patterns. We used genetic analyses to infer the prevailing colonization pattern of the epiphytic orchid, Brassavola nodosa. Samples from three populations (i.e. individuals within a tree) from each of five pastures in the dry forest of Costa Rica were genotyped with neutral nuclear and chloroplast markers. Spatial autocorrelation and hierarchical genetic structure analyses were used to assess the relatedness of individuals within populations, among populations within pastures and among populations in different pastures. The results showed significant relatedness within populations (mean r = 0.166) and significant but lower relatedness among populations within a pasture (mean r = 0.058). Our data suggest that colonization of available habitats is by few individuals with subsequent population expansion resulting from in situ reproduction, and that individuals within a tree are not a random sample of the regional seed pool. Furthermore, populations within a pasture were likely colonized by seeds produced by founders of a neighbouring population within that pasture. These results have important ramifications for understanding conservation measures needed for this species and other epiphytic orchids.

空生境定殖是影响物种在持续变化的景观中存续并发生分布范围调整的核心生态过程。因此，解析影响乃至限制定殖过程的相关因素，具有重要的生态学与保护生物学意义。附生兰科植物正日益受到各类因素的威胁，其中包括人为活动引发的生境干扰。随着受清理区域（如牧场）被适宜的宿主树木重新定植，附生兰种群的建立过程与遗传组成，大概率与其定殖模式密切相关。本研究通过遗传分析，推断附生兰Brassavola nodosa的主流定殖模式。我们采集了哥斯达黎加干旱森林中5个牧场的样本：每个牧场内选取3个种群（即单株宿主树木上的个体），并采用中性核基因及叶绿体分子标记完成基因分型。通过空间自相关分析与层级遗传结构分析，我们评估了种群内个体间、牧场内种群间以及不同牧场间种群的亲缘关系。研究结果显示，种群内个体间存在显著的亲缘相关性（平均亲缘相关系数r=0.166），而牧场内种群间的亲缘相关性同样显著，但程度更低（平均亲缘相关系数r=0.058）。我们的数据表明，可利用生境的定殖由少数奠基个体完成，后续种群扩张则源于原位繁殖；且单棵宿主树木上的个体并非区域种子库的随机取样样本。此外，同一牧场内的不同种群，大概率由该牧场内邻近种群的奠基个体所产生的种子完成定殖。上述结果对于明确该物种及其他附生兰科植物的保护策略具有重要的参考价值与启示意义。