Data from: Speciation in a keystone plant genus is driven by elevation: a case study in New Guinean Ficus

Much of the world's insect and plant biodiversity is found in tropical and subtropical ‘hotspots’, which often include long elevational gradients. These gradients may function as ‘diversity pumps’ and contribute to both regional and local species richness. Climactic conditions on such gradients often change rapidly along short vertical distances, and may result in local adaptation and high levels of population genetic structure in plants and insects. We investigated the population genetic structure of two species of Ficus (Moraceae) along a continuously forested elevational gradient in Papua New Guinea. This speciose plant genus is pollinated by tiny, species specific and highly co-evolved chalcid wasps (Agaonidae) and represented by at least 73 species at our study gradient. We present results from two species of Ficus sampled from six elevations between 200 m-2,700 m a.s.l. (almost the entire elevational range of the genus) and 10 polymorphic microsatellite loci. These results show that strong barriers to gene flow exist between 1,200 m and 1,700 m a.s.l. Whereas lowland populations are panmictic across distances over 70 km, montane populations can be disjunct over 4 km, despite continuous forest cover. We suggest that the limited gene flow between populations of these two species of montane Ficus maybe driven by environmental limitations on pollinator or seed dispersal in combination with local adaptation of Ficus populations. Such a mechanism may have wider implications for plant and pollinator speciation across long and continuously forested elevational gradientsif generalist insect pollinators and vertebrate seed dispersers also form populations based on elevation.全球绝大多数昆虫与植物生物多样性均分布于热带、亚热带生物多样性热点区域（hotspots），这类区域往往伴随狭长的海拔梯度。此类梯度或可充当"多样性泵"，同时提升区域与局域的物种丰富度。沿此类梯度的气候条件常在极短的垂直距离内发生剧烈变化，可能促使植物与昆虫产生本地适应，并形成高度分化的种群遗传结构。 本研究针对巴布亚新几内亚一条连续森林覆盖的海拔梯度上的两种桑科（Moraceae）榕属（Ficus）植物开展种群遗传结构分析。该物种丰富度极高的植物类群由专性且高度协同演化的小型榕小蜂（Agaonidae）传粉，在本次研究的海拔梯度上至少分布有73个物种。 本次研究选取该梯度上海拔200米至2700米（几乎覆盖该属完整海拔分布范围）间6个海拔点位的两种榕属植物样本，结合10个多态性微卫星位点（microsatellite loci）开展分析。结果显示，在1200米至1700米海拔区间存在显著的基因流阻隔屏障。低海拔种群在70公里以上的范围内仍保持随机交配状态，而山地种群即便处于连续森林覆盖的环境中，种群间仅间隔4公里便呈现遗传分化。 我们推测，这两种山地榕属植物种群间有限的基因流，或由传粉者或种子传播者的环境限制，结合榕属种群的本地适应共同驱动。若广食性昆虫传粉者与脊椎动物种子传播者同样会依据海拔形成种群分化，该机制或对连续长距离森林海拔梯度上的植物与传粉者物种形成过程具有更广泛的启示意义。