Environmental variation in sex ratios and sexual dimorphism in three wind-pollinated dioecious plant species

We counted males and females and measured plant traits at 14 naturally occurring populations of R. lunaria on the island of Tenerife (Spain) in April 2017, at eleven populations of U. dioica in ‘Le Plateau’ area (Switzerland) in September 2017, and at ten populations of S. helvetica in the Alps (Switzerland) in July 2017. To ensure an unbiased sample, we recorded the sex of every individual identified, moving through the populations in only one direction to avoid sampling any individual more than once. For each species, we counted all individuals up to a maximum of 150 per population. Plant height and canopy width were recorded for all sampled mature flowering individuals in R. lunaria and S. helvetica. For U. dioica, due to its clonal habits, we estimated plant cover for roughly half of the mature individuals identified, using a visual criterion to determine the shape best approximating the plant cover per individual (e.g., circle, ellipse, or rectangle), and we further measured the parameters of the projected shape to assess their cover. For each population, we calculated the operational sex ratio (SR) as the proportion of females divided by the total number of flowering individuals in a population. We further calculated, for each population, two sexual dimorphism indices, one for leaf area and one for plant size, hereafter termed SLD and SSD, respectively. The SLD and SSD were calculated as the log of the ratio of the mean female to the mean male leaf area or plant size, respectively (Smith 1999), with a null expectation of 0 for no difference. We extracted for each population ten bioclimatic variables at a spatial resolution of 1 km 2 from WorldClim global climate layers (Fick and Hijmans 2017) and calculated the principal components (PC) axes of the bioclimatic variables. Please, find additional details in the Readme file and in the article: Bürli, S., Pannell, J. R., & Tonnabel, J. (2022). Environmental variation in sex ratios and sexual dimorphism in three wind‐pollinated dioecious plant species. Oikos, e08651. https://doi.org/10.1111/oik.08651

2017年4月，我们在西班牙特内里费岛的14个天然种群中对R. lunaria开展了雌雄个体计数与植物性状测定；2017年9月，在瑞士‘高原（Le Plateau）’区域的11个U. dioica种群完成了相关数据采集；2017年7月，于瑞士阿尔卑斯山区的10个S. helvetica种群进行了样本收集与测定。为保证样本无偏性，我们对所有鉴定出的个体记录其性别，并仅沿单一方向遍历种群，以避免对同一个体重复采样。针对每个物种，我们对种群内所有个体进行计数，单一种群的采样上限为150株。对于R. lunaria和S. helvetica的所有采样成熟开花个体，我们记录了其株高与冠幅。鉴于U. dioica具有克隆生长习性，我们对约半数鉴定出的成熟个体开展了植株盖度估算：通过视觉判断选取最贴合单株盖度的几何形状（如圆形、椭圆形或矩形），并进一步测量该投影形状的参数以量化其盖度。针对每个种群，我们计算了功能性性别比（operational sex ratio, SR），其值为种群内雌性个体数与开花个体总数的比值。我们还针对每个种群计算了两项性别二态性指数，分别对应叶面积与植株体型，后文分别记为SLD与SSD。SLD与SSD的计算方式为：雌性平均叶面积与雄性平均叶面积的比值、雌性平均植株体型与雄性平均植株体型的比值的自然对数（Smith等，1999），当无性别差异时，理论预期值为0。我们从WorldClim全球气候数据集（Fick与Hijmans，2017）中提取了每个种群的10个生物气候变量，空间分辨率为1 km²，并对这些生物气候变量进行主成分分析（principal components, PC）以获取主成分轴。更多详细信息请参见数据集说明文件（Readme）以及下述文献：Bürli S, Pannell J R, Tonnabel J. 2022. 三种风媒雌雄异株植物的性比与性别二态性随环境的变化. Oikos, e08651. https://doi.org/10.1111/oik.08651