Williams Jennifer L
Division of Biological Sciences, University of Montana, Missoula, Montana 59812, USA.
Am Nat. 2009 Nov;174(5):660-72. doi: 10.1086/605999.
Life-history theory makes several key predictions about reproductive strategies on the basis of demographic vital rates, particularly the relationship between juvenile and adult survival. Two such predictions concern the optimal time to begin reproducing and whether semelparity or iteroparity is favored. I tested these life-history predictions and explored how they might differ between the native and introduced ranges of the monocarpic perennial Cynoglossum officinale. I first compared vital rates between ranges. I then used these vital rates to parameterize integral projection models to calculate the population growth rate (lambda) and net reproductive rate (R(0)) as surrogates for fitness to compare strategies within and between ranges. I found that both survival and growth were higher in the introduced range, where size at flowering was larger and iteroparity was much more common than in the native range. The observed and predicted strategies for size at flowering were similar in the native range. In the introduced range, however, even though plants flowered at a larger size, the observed size was not as large as the optimum predicted by lambda or the higher optimum predicted by R(0). Iteroparity conferred higher fitness in both ranges, as measured by both fitness metrics, suggesting that severe constraints, potentially specialist herbivores, prevent this strategy from becoming more common in the native range.
生活史理论基于人口统计学的生命率，特别是幼体与成体存活率之间的关系，对繁殖策略做出了几个关键预测。其中两个预测涉及开始繁殖的最佳时间以及单次繁殖或多次繁殖哪种更受青睐。我检验了这些生活史预测，并探讨了它们在单果多年生植物药用琉璃草的原生分布区和引入分布区可能存在的差异。我首先比较了两个分布区的生命率。然后，我用这些生命率对积分投影模型进行参数化，以计算种群增长率（λ）和净繁殖率（R₀），作为适合度的替代指标，来比较分布区内和分布区之间的策略。我发现，在引入分布区，存活率和生长率都更高，在引入分布区，开花时的植株大小更大，多次繁殖也比原生分布区更为常见。在原生分布区，观察到的和预测的开花植株大小策略相似。然而，在引入分布区，尽管植株开花时的大小更大，但观察到的大小并不像由λ预测的最优值或由R₀预测的更高最优值那么大。用两种适合度指标衡量，多次繁殖在两个分布区都赋予了更高的适合度，这表明严重的限制因素，可能是专性食草动物，阻止了这种策略在原生分布区变得更为常见。
