Collaborative Research: Extinction Dynamics and Population Bottlenecks in an Annual Plant with Seed Bank

9421605 McPEEK 许多生物体栖息的环境中，生态条件每年都有很大的波动。 在某些年份，环境条件可能是良性的，因此为人口增长创造了有利条件，而在其他年份，环境条件可能是不适宜的，因此导致人口增长率下降。 通过迫使一个种群在某些年份变得非常小，这种变异性将增加整个种群灭绝的机会，并促进遗传变异的丧失。 栖息在长期变化的环境中的物种通常具有适应性，这些适应性应该缓冲环境变化的不利影响。 这项拟议中的研究将测试其中一种适应措施的有效性，即一年生植物的土壤种子库。 种子银行是存在的休眠，可行的种子储存在土壤中。 由于一年中产生的所有种子不会在下一个生长季节发芽，种子库创造了年龄结构，有效地将再生努力（以及灭绝的风险）分散在多年中。 将进行两项研究。 第一，将建立实验种子库，以评估五年内从种子库发芽的种子的人口和遗传动态。 在另一项研究中，研究人员将建立多个重复种群，实验性地对一半种群实施成年灭绝，而另一半种群则不受控制。 将在五年内对这些实验人群的人口统计学和遗传动态进行量化。 从这两项研究中，将构建一个完整的描述大环境扰动的遗传和人口后果。 这项研究是第一个经验性的评估种子银行的影响，在自然植物种群的人口和进化过程。 这项研究的结果将对未来种子库效应的理论发展和珍稀濒危物种的保护具有重要意义，包括植物和动物，生活在长期变化和不可预测的环境中。

9421605 McPEEK Many organisms inhabit environments in which ecological conditions fluctuate greatly from year to year. In some years environmental conditions may be benign and therefore foster favorable conditions for population growth, while conditions in other years may be inhospitable and consequently result in declining population growth rates. By forcing a population to very small sizes in some years, such variability will heighten the chances of total population extinction and promote the loss of genetic variation. Species inhabiting chronically variable environments often possess adaptations which should buffer these detrimental effects of environmental variability. The proposed research will test the effectiveness of one of these adaptations, the soil seed bank of annual plants. Seed banks are the presence of dormant, viable seeds stored in the soil. Since all seeds produced in one year do not germinate in the following growing season, seed banks create age structure which effectively spreads the regenerative effort (and thus the risk of extinction) over multiple years. Two studies will be performed. In one, experimental seed banks will be constructed to evaluate the demographic and genetic dynamics of seeds germinating from the seed bank over five years. In the other study, the investigators will establish multiple replicate populations, experimentally impose adult extinction on half, and leave the other half unmanipulated. The demographic and genetic dynamics will be quantified for these experimental populations over five years. From these two studies a complete description of the genetic and demographic consequences of large environmental perturbations will be constructed. This research represents one of the first empirical evaluations of the effects of seed banks on the demographic and evolutionary processes in natural plant populations. The results of this study will have important implications for future theoretical development of the effects of seed banks an d for the conservation of rare and endangered species, both plants and animals, living in chronically variable and unpredictable environments.