PREMISE Spatial variation in selective pressures can lead to intraspecific variation in life history, favoring some life histories and constraining others depending on the vulnerability of life stages. We examined how spatial variation in herbivory and climate influences flowering size and the occurrence of semelparity (reproducing once) versus iteroparity (reproducing multiple times) in the introduced range of an invasive plant, houndstongue (Cynoglossum officinale). Houndstongue is a short-lived, semelparous perennial in its native range. In its introduced range, we previously documented increased rates of iteroparity and a higher median threshold flowering size compared to the native range. We hypothesized that the recent introduction of a specialist biocontrol insect (a root-boring weevil, Mogulones crucifer) would decrease threshold flowering size and reduce the proportion of iteroparous plants because M. crucifer preferentially attacks large individuals and may reduce overwinter survival. METHODS We surveyed 24 sites across the northwestern United States to quantify the frequency of semelparity versus iteroparity and to estimate weevil abundance and used demographic data collected from six sites to estimate median threshold flowering size. RESULTS We found that sites with greater winter precipitation and no weevils had a greater proportion of iteroparous plants. Sites with higher weevil attack had a lower median threshold flowering size. CONCLUSIONS The variation in frequency of flowering and threshold flowering size that we documented in North American houndstongue populations, and the relationships between this variation and herbivory and climate, provide evidence for how selective pressures covary with the life histories of invasive plants.

中文翻译：

---

入侵植物的生活史变异与气候和近期特定食草动物的定植有关

前提 选择压力的空间变化会导致生活史的种内变化，根据生命阶段的脆弱性，有利于某些生活史并限制其他生活史。我们研究了食草动物和气候的空间变化如何影响引入的入侵植物猎犬 (Cynoglossum officinale) 范围内的开花大小和同胎性（繁殖一次）与迭代性（繁殖多次）的发生。猎犬在其原生范围内是一种短命的半生多年生植物。在其引入的范围内，我们之前记录了与原生范围相比增加的迭代率和更高的中值阈值开花大小。我们假设最近引入了一种专门的生物防治昆虫（一种蛀根象鼻虫，Mogulones crucifer) 将降低阈值开花大小并减少迭代生育植物的比例，因为 M. crucifer 优先攻击大型个体并可能降低越冬存活率。方法我们调查了美国西北部的 24 个地点，以量化半次生次与重复性次生的频率并估计象鼻虫的丰度，并使用从六个地点收集的人口统计数据来估计中值阈值开花大小。结果我们发现，冬季降水量较大且没有象鼻虫的地点具有较大比例的轮生植物。具有较高象鼻虫攻击的站点具有较低的中值阈值开花大小。结论 我们在北美猎犬种群中记录的开花频率和阈值开花大小的变化，