Prior Carly J, Busch Jeremiah W
School of Biological Sciences, Washington State University, Pullman, WA, 99164, USA.
Am J Bot. 2021 Nov;108(11):2294-2308. doi: 10.1002/ajb2.1766. Epub 2021 Nov 21.
In plants, populations and species vary widely along the continuum from outcrossing to selfing. Life-history traits and ecological circumstances influence among-species variation in selfing rates, but their general role in explaining intraspecific variation is unknown. Using a database of plant species, we test whether life-history traits, geographic range position, or abundance predict selfing rate variation among populations.
We identified species where selfing rates were estimated in at least three populations at known locations. Two key life-history traits (generation time and growth form) were used to predict within-species selfing rate variation. Populations sampled within a species' native range were assessed for proximity to the nearest edge and abundance. Finally, we conducted linear and segmented regressions to determine functional relationships between selfing rate and geographic range position within species.
Selfing rates for woody species varied less than for herbs, which is explained by the lower average selfing rate of woody species. Relationships between selfing and peripherality or abundance significantly varied among species in their direction and magnitude. However, there was no general pattern of increased selfing toward range edges. A power analysis shows that tests of this hypothesis require studying many (i.e., 40+) populations.
Intraspecific variation in plant mating systems is often substantial yet remains difficult to explain. Beyond sampling more populations, future tests of biogeographic hypotheses will benefit from phylogeographic information concerning specific range edges, the study of traits influencing mating system (e.g., herkogamy), and measures of abundance at local scales (e.g., population density).
在植物中，种群和物种在从异交到自交的连续统上差异很大。生活史特征和生态环境影响着物种间自交率的变化，但其在解释种内变异方面的总体作用尚不清楚。利用一个植物物种数据库，我们测试生活史特征、地理分布范围位置或丰度是否能预测种群间的自交率变化。
我们确定了在已知地点的至少三个种群中估计出自交率的物种。使用两个关键的生活史特征（世代时间和生长形式）来预测种内自交率的变化。评估一个物种原生范围内采样的种群与最近边缘的距离和丰度。最后，我们进行线性和分段回归，以确定物种内自交率与地理分布范围位置之间的功能关系。
木本物种的自交率变化小于草本物种，这可以用木本物种较低的平均自交率来解释。自交与边缘性或丰度之间的关系在物种间的方向和程度上有显著差异。然而，并没有朝着分布范围边缘自交增加的一般模式。功效分析表明，对这一假设的检验需要研究许多（即40个以上）种群。
植物交配系统的种内变异通常很大，但仍然难以解释。除了对更多种群进行采样外，未来生物地理学假设的检验将受益于有关特定分布范围边缘的系统发育地理信息、影响交配系统的性状（如雌雄异位）的研究以及局部尺度上的丰度测量（如种群密度）。
