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

9421781卡利兹许多生物生活在生态条件年年变化很大的环境中。在某些年份，环境条件可能是良好的，因此为人口增长创造了有利条件，而在其他年份，环境条件可能不适宜居住，从而导致人口增长率下降。通过迫使种群在某些年份变得非常小，这种变异性将增加总种群灭绝的可能性，并促进遗传变异的丧失。生活在长期多变环境中的物种往往具有适应能力，这应该可以缓冲环境变异性的这些有害影响。这项拟议的研究将测试其中一项适应的有效性，即一年生植物的土壤种子库。种子库是储存在土壤中的休眠的、有活力的种子的存在。由于一年产生的所有种子不会在下一个生长季节发芽，种子库产生的年龄结构有效地将再生努力(因此灭绝的风险)分散到多年。将进行两项研究。首先，将建立试验性种子库，以评估在五年内从种子库中萌发的种子的人口统计学和遗传动力学。在另一项研究中，研究人员将建立多个复制种群，以试验性的方式将成虫灭绝，而不对另一半进行操纵。这些实验种群的人口统计和遗传动态将在五年内得到量化。根据这两项研究，将对大规模环境扰动的遗传和人口后果进行完整的描述。这项研究是对种子库对自然植物种群的人口统计和进化过程的影响的第一次经验评估之一。这项研究的结果将对未来种子库效应的理论发展和保护生活在长期多变和不可预测的环境中的稀有和濒危物种，包括植物和动物具有重要意义。

9421781 KALISZ 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.