Maron John L, Kauffman Matthew J
Division of Biological Sciences, University of Montana, Missoula 59812, USA.
Ecology. 2006 Jan;87(1):113-24. doi: 10.1890/05-0434.
Multiple consumers often attack seeds, seedlings, and adult plants, but their population-level consequences remain uncertain. We examined how insect and small mammal consumers influenced the demography and abundance of the perennial shrub, bush lupine (Lupinus arboreus). In grassland and dune habitats we established replicate experimental lupine populations in 81-m2 plots that were either protected from, or exposed to, herbivorous voles and granivorous mice (via fencing) and/or root feeding insects (via insecticide treatment). Populations were initiated with transplanted seedlings in 1999 and 2000. We followed the demography of these cohorts, subsequent generations, and the seed bank for 5.5 years. Voles and insects killed many seedlings in dune (1999 only) and grassland (1999 and 2000) habitats. After 2000, insects and voles had minimal effects on seedling or adult survival. Seed predation by granivorous mice, however, greatly depressed seedling recruitment, resulting in lower adult lupine abundance in control plots vs. those protected from rodents. In grasslands, initial effects of voles and insects on seedling survival produced large differences among treatments in adult plant density and the cumulative number of seeds produced throughout the experiment. Differences among grassland populations in seed rain, however, had little influence on the magnitude of seedling recruitment into this habitat. Instead, recruitment out of a preexisting seed bank compensated for the lack of seed production in populations exposed to consumers. Shading by dense adults in plots protected from consumers limited seedling establishment within these populations. Although differences among populations in cumulative seed rain did not influence adult establishment, populations protected from consumers accumulated substantially larger seed banks than controls. These results illustrate how density dependence, habitat-specific seed dynamics, and particular demographic impacts of consumers interact to shape plant population responses to consumers.
多种消费者常常会攻击种子、幼苗和成年植株，但其在种群水平上的影响仍不明确。我们研究了昆虫和小型哺乳动物消费者如何影响多年生灌木——滨海羽扇豆（Lupinus arboreus）的种群统计学特征和数量。在草原和沙丘栖息地，我们在81平方米的地块中建立了重复的实验羽扇豆种群，这些地块要么通过围栏防止食草田鼠和食谷小鼠进入，要么让其暴露在外，并且/或者通过杀虫剂处理来防治根部取食昆虫。种群于1999年和2000年通过移栽幼苗开始建立。我们对这些种群、后代以及种子库进行了5.5年的种群统计学跟踪。田鼠和昆虫在沙丘（仅1999年）和草原（1999年和2000年）栖息地杀死了许多幼苗。2000年之后，昆虫和田鼠对幼苗或成年植株存活的影响极小。然而，食谷小鼠的种子捕食极大地抑制了幼苗补充，导致对照地块中的成年羽扇豆数量低于防鼠地块。在草原上，田鼠和昆虫对幼苗存活的初始影响在成年植株密度以及整个实验期间产生的种子累计数量方面造成了各处理间的巨大差异。然而，草原种群间种子雨的差异对该栖息地幼苗补充的规模影响很小。相反，来自现有种子库的补充弥补了受消费者影响种群中种子产量的不足。在防消费者地块中，茂密成年植株的遮荫限制了这些种群内的幼苗建立。尽管种群间累计种子雨的差异并未影响成年植株的建立，但防消费者地块比对照地块积累了大得多的种子库。这些结果说明了密度依赖性、特定栖息地的种子动态以及消费者的特定种群统计学影响如何相互作用，从而塑造植物种群对消费者的反应。
