The ABCs of Dispersal: Developing an Approximate Bayesian Computation Approach for Estimating Migration Rates from the Distribution of Related Individuals

估计个体动物在种群和栖息地之间的迁移率是保护生物学中的一个关键问题，对于确定高质量的栖息地和确定是否可以通过其他种群的移民来拯救种群的减少是必要的。该项目的目标是发展一种新的统计和遗传框架，以改进对生物在种群或栖息地之间扩散速率的估计。提出的方法包括将遗传方法确定的相关个体的空间分布转化为迁移率的估计。例如，如果一个亲本和它的后代出现在两个不同的种群或栖息地，那么一定发生了运动事件。这种新方法将通过对生活在哥斯达黎加遮荫农业生态系统中的霍夫曼二趾树懒和棕喉三趾树懒的运动和人口统计学研究进行测试。这两个物种的几百只个体将在阴凉的可可树、完整的森林和牛牧场被捕获；将对雄性进行无线电标记，对雌性进行颜色标记，以便估计三种栖息地类型的出生率和死亡率。将收集小的组织样本进行遗传分析，这将提供有关相对远亲个体的信息和对运动速度的精确估计。这三种栖息地类型之间的关系模式将被用来确定迁徙的幅度和方向，并最终确定树荫农业对这些敏感而有魅力的热带哺乳动物的价值。荫蔽农业越来越多地被认为是保护热带生物多样性的一种手段，但是关于这种农业做法对敏感物种的益处的详细生态研究还没有进行。由于树懒久坐不动，生活在树上，因此它们是保护工作中有用的保护伞物种；如果遮荫种植的农业能够在破碎的景观中维持树懒种群的生存，那么农业实践可以使一系列额外的热带物种受益。本项目开发的统计和遗传方法将适用于一系列物种，并将通过可免费下载的软件包向公众提供。该项目将加强与哥斯达黎加研究人员的研究和培训合作，并将为两名博士后学者提供研究培训和指导。

Estimating rates of movements of individual animals among populations and habitats is a critical issue in conservation biology, necessary for identifying high quality habitats and determining if declining populations can be rescued by immigration from other populations. The goal of this project is to develop a novel statistical and genetic framework that would improve estimation of dispersal rates for organisms among populations or habitats. The proposed approach involves translating the spatial distribution of related individuals identified with genetic methods into estimates of migration rates. If, for example, a parent and its offspring occur in two different populations or habitats, a movement event must have occurred. This new methodology will be tested through a study of the movements and demographics of Hoffmann's two-toed sloths and brown-throated three-toed sloths living in a shade-grown agricultural ecosystem in Costa Rica. Several hundred individuals of both species will be captured in shade-grown cacao, intact forest, and cattle pastures; males will be radio-tagged and females will be color-marked in order to estimate birth and death rates in the three habitat types. Small tissue samples will be collected for genetic analyses that will provide information about relatively distantly related individuals and precise estimates of movement rates. Patterns of relatedness among the three habitat types will be used to determine the magnitude and direction of movements, and ultimately determine the value of shade-grown agriculture to these sensitive and charismatic tropical mammals. Shade-grown agriculture is increasingly pointed to as a means for protecting tropical biodiversity, but detailed ecological studies of the benefits of such agricultural practices to sensitive species have not been conducted. Because of their sedentary and obligate arboreal life style, sloths are a useful umbrella species for conservation efforts; if shade-grown agriculture can maintain viable sloth populations within fragmented landscapes then agricultural practices could benefit a range of additional tropical species. The statistical and genetic approach developed in this project will be applicable to a range of species and will be made publically accessible via a freely downloadable software package. This project will strengthen research and training collaborations with Costa Rican researchers and will provide research training and mentoring for two postdoctoral scholars.