Data from: Persistence of long-distance, insect-mediated pollen movement for a tropical canopy tree species in remnant forest patches in an urban landscape

As deforestation and urbanization continue at rapid rates in tropical regions, urban forest patches are essential repositories of biodiversity. However, almost nothing is known about gene flow of forest-dependent tree species in urban landscapes. In this study, we investigated gene flow in the insect-pollinated, wind-dispersed tropical tree Koompassia malaccensis in and among three remnant forest patches in the urbanized landscape of Singapore. We genotyped the vast majority of adults (N=179) and a large number of recruits (N=2103) with 8 highly polymorphic microsatellite markers. Spatial genetic structure of the recruit and adult cohorts was significant, showing routine gene dispersal distances of ~100–400 m. Parentage analysis showed that 97% of recruits were within 100 m of their mother tree, and a high frequency of relatively short-distance pollen dispersal (median ~143–187 m). Despite routine seed and pollen dispersal distances of within a few hundred meters, interpatch gene flow occurred between all patches and was dominated by pollen movement: parentage analysis showed 76 pollen versus 2 seed interpatch dispersal events, and the seedling neighborhood model estimated ~1–6% seed immigration and ~21–46% pollen immigration rates, depending on patch. In addition, the smallest patch (containing five adult K. malaccensis trees) was entirely surrounded by >2.5 km of ‘impervious’ substrate, yet had the highest proportional pollen and seed immigration estimates of any patch. Hence, contrary to our hypothesis, insect-mediated gene flow persisted across an urban landscape, and several of our results also parallel key findings from insect-pollinated canopy trees sampled in mixed agricultural–forest landscapes.随着热带地区森林砍伐与城市化进程持续加速，城市森林斑块已然成为生物多样性的核心储存库。然而，当前学界对城市景观中依赖森林的树种的基因流特征几乎尚无系统性认知。本研究以新加坡城市化景观内的3处残留森林斑块为研究对象，针对其中的虫媒风播热带树种马来甘巴豆（Koompassia malaccensis）展开调查。研究团队采用8个高度多态性的微卫星标记（microsatellite markers），对绝大多数成年个体（N=179）与大量更新幼苗（N=2103）进行了基因分型。分析结果显示，更新幼苗组与成年个体组均呈现显著的空间遗传结构（spatial genetic structure），表明该树种的常规基因扩散距离约为100~400米。亲权分析（parentage analysis）结果表明，97%的更新幼苗与其母树的空间距离在100米以内，且花粉扩散以短距离为主，扩散中位数约为143~187米。尽管该树种的常规种子与花粉扩散距离均在数百米范围内，但所有研究斑块之间均发生了斑块间基因流，且该基因流以花粉移动为主导：亲权分析共检出76次花粉跨斑块扩散事件与2次种子跨斑块扩散事件；幼苗邻域模型（seedling neighborhood model）估算结果显示，依斑块不同，种子迁入率约为1%~6%，花粉迁入率约为21%~46%。此外，面积最小的斑块（仅包含5株成年马来甘巴豆个体）完全被长度超过2.5千米的不透水基质环绕，但其花粉与种子的相对迁入率却是所有斑块中最高的。综上，与本研究的初始假设相悖，昆虫介导的基因流可在城市景观中持续发生；同时，本研究的多项关键结果也与农林混合景观中虫媒冠层树种的相关研究结论高度契合。