Data from: Relative importance of pollen and seed dispersal across a Neotropical mountain landscape for an epiphtytic orchid.

Populations of many species are isolated within narrow elevation bands of Neotropical mountain habitat, and how well dispersal maintains genetic connectivity is unknown. We asked whether genetic structure of an epiphytic orchid, Epidendrum firmum, corresponds to gaps between Costa Rican mountain ranges, and how these gaps influence pollen and seed flow. We predicted that significant genetic structure exists among mountain ranges due to different colonization histories and limited gene flow. Furthermore, we predicted that pollen movement contributes more to gene flow than seeds because seeds are released into strong winds perpendicular to the narrow northwest-southeast species distribution, while the likely pollinators are strong fliers. Individuals from 12 populations and three mountain ranges were genotyped with nuclear microsatellites (nDNA) and chloroplast sequences (cpDNA). Genetic diversity was high for both markers, while nDNA genetic structure was low (FSTn = 0.020) and cpDNA structure was moderate (FSTc = 0.443). Significant cpDNA barriers occurred within and among mountain ranges, but nDNA barriers were not significant after accounting for geographic distance. Consistent with these contrasting patterns of genetic structure, pollen contributes substantially more to gene flow among populations than seed (mp/ms = 46). Pollinators mediated extensive gene flow, eroding nDNA colonization footprints, while seed flow was comparatively limited, possibly due to directional prevailing winds across linearly distributed populations. Dispersal traits alone may not accurately inform predictions about gene flow or genetic structure, supporting the need for research into the potentially crucial role of pollinators and landscape context in gene flow among isolated populations.

诸多物种的种群均隔离分布于新热带区山地生境的狭窄海拔带内，目前学界尚未明确扩散作用对遗传连通性的维持效果。本研究以附生兰（epiphytic orchid）硬皮兰（Epidendrum firmum）为研究对象，探究其遗传结构是否与哥斯达黎加各山脉间的地理间隔相契合，以及此类间隔如何影响花粉与种子的扩散流。我们预测，由于各山脉间种群的殖民历史存在差异且基因流受限，不同山脉间会出现显著的遗传结构分化。此外，我们还预测花粉传播对基因流的贡献度高于种子：因种子会被释放至与该物种狭窄的西北-东南分布方向垂直的强风环境中，而其潜在传粉者均具备较强的飞行能力。研究对采自3个山脉共12个种群的个体，采用核微卫星（nuclear microsatellites，nDNA）与叶绿体序列（chloroplast sequences，cpDNA）进行基因分型。两种标记的遗传多样性均较高；其中核DNA的遗传结构分化程度较低（FSTn = 0.020），而叶绿体DNA的分化程度中等（FSTc = 0.443）。叶绿体DNA检测到山脉内部及山脉间存在显著的遗传屏障，但在考虑地理距离的影响后，核DNA的遗传屏障不再显著。与上述遗传结构的差异模式一致，种群间的基因流主要由花粉传播贡献（mp/ms = 46）。传粉者介导了广泛的基因流，抵消了核DNA所记录的殖民历史印记；而种子流则相对有限，这可能是因为线性分布的种群会受到定向盛行风的影响。仅依靠扩散特征或许无法准确预测基因流与遗传结构，这表明有必要深入探究传粉者与景观背景在隔离种群间基因流中所发挥的潜在关键作用。