CRB: Population Size and Density Effects on Population Viability: A Case Study of Two Cirsium Species

随着时间的推移，在一个地方，常见物种往往保持常见，而稀有物种仍然罕见。生物学家长期以来一直对确定哪些因素或过程调节或控制种群大小感兴趣。最近，人类活动减少某些物种丰富度的影响变得更加明显。随着人们对保护生物多样性的兴趣日益浓厚，人们开始试图确定影响稀有和濒危物种生存的因素。本研究探讨了种群大小对种群内单株生长性能的影响。新墨西哥州山区的两种蓟将被研究：一种是稀有物种（作为联邦濒危物种受到保护），另一种是类似环境中更常见的蓟。将从已知的稀有物种种群中选择不同大小的种群（从10只到3000多只不等）；将对这些种群中的单个植物进行监测。将对常见物种的人工种群进行类似的观察，这些种群将由研究者移植的植物建立。对这些种群的存活率、种子产量等的估计将被用于计算机模型中，以评估这些受威胁物种的极小种群的生存能力（持续存在的机会）。这项研究将阐明调节植物种群大小的过程，包括常见的和罕见的。这项研究还将测试评估小种群生存能力的方法。这些技术对于土地管理者和政府机构决定哪些物种或种群值得进行保护工作至关重要。

Over time in a location, common species tend to remain common while rare species remain rare. Biologists have long been interested in determining what factors or processes regulate or control population size. Recently, the effect of human activities in decreasing the abundance of some species has become more apparent. With increasing interest in protecting biological diversity has come an attempt to identify the factors affecting the survival of rare and endangered species. This research investigates the effects of population size on the performance of individual plants within those populations. Two species of thistle occurring in the mountains of New Mexico will be studied: one a rare species (protected as a federally Threatened species) and the other a more common thistle of similar environments. Populations of different sizes (ranging from 10 to over 3000 individuals) will be selected from known populations of the rare species; individual plants within these populations will be monitored. Similar observation will be carried out on artificial populations of the common species, which will be established with plants transplanted by the investigator. Estimates of the rates of survival, seed production, and so on in these populations will be used in computer models to assess the viability (the chances for continued persistence) of extremely small populations of the threatened species. This research will shed light on the processes that regulate population size in plants, both common and rare. The research will also test methods for assessing the viability of small populations. Such techniques are essential for land managers and government agencies making decisions about which species or populations are worthy candidates for conservation efforts.