Center for Population Biology, University of California Davis, Davis, California 95616.
Am J Bot. 1999 Jan;86(1):131-9.
The magnitude of inbreeding depression in invading plant populations is often presumed to be small and of little consequence. The purpose of this study was to assess the magnitude of inbreeding depression in a pollen-limited, partially self-incompatible, invading plant population. The magnitude and timing of inbreeding depression were compared among ten maternal plants sampled from a population of smooth cordgrass (Spartina alterniflora) invading San Francisco Bay. Selfed and outcrossed progeny were compared for embryo abortion, survival of seedlings, and growth/survival at the end of the first growing season in three greenhouse environments. Estimates of inbreeding depression varied among environments, with competitive environment > high-nutrient environment > low-nutrient environment. Population-level estimates of inbreeding depression ranged from 0.61 to 0.81; however, maternal plants varied significantly in their magnitude of inbreeding depression, ranging from 0.1 to 0.97. The 95% confidence interval for inbreeding depression for some maternal plants included zero. There was a significant negative correlation between the overall magnitude of inbreeding depression and self-fertility rate among maternal plants. The few maternal plants with high self-fertility carried relatively little genetic load, and their selfed progeny are likely to survive on open mudflats. The noncompetitive, pollen-limited growing conditions associated with invasion may allow self-fertility to spread in this population.
在入侵植物种群中，近亲繁殖衰退的程度通常被认为较小，影响不大。本研究旨在评估一个花粉限制、部分自交不亲和的入侵植物种群中近亲繁殖衰退的程度。从入侵旧金山湾的光滑雀稗（Spartina alterniflora）种群中抽取的 10 株母株，比较了近亲繁殖和异交后代的胚胎夭折、幼苗存活率以及在三个温室环境下第一个生长季节结束时的生长/存活率。在竞争环境>高养分环境>低养分环境中，近亲繁殖衰退的估计值在环境间存在差异。种群水平的近亲繁殖衰退估计值范围为 0.61 至 0.81；然而，母株在近亲繁殖衰退的程度上存在显著差异，范围为 0.1 至 0.97。一些母株的近亲繁殖衰退的 95%置信区间包含零。母株的整体近亲繁殖衰退程度与自交率之间存在显著的负相关关系。少数具有高自交率的母株携带的遗传负荷相对较小，其自交后代可能在开阔的泥滩上存活。与入侵相关的非竞争、花粉限制的生长条件可能允许自交在该种群中传播。
