Dissertation Research: Linking climate dynamics and historical demographic in South American forest lizards

数万年前，南美洲东北部的降雨量远高于今天。结果，亚马逊和大西洋雨林更加广阔，占据了今天被沙漠和热带草原覆盖的地区。当气候变得干燥时，这些森林收缩并变得支离破碎。这种变化可能对生活在热带雨林中的动植物产生了巨大的影响。该项目探讨了热带森林生物如何受到过去25万年来气候变化的影响。研究人员将研究巴西森林中三种蜥蜴的基因组，并通过比较每个物种在其地理范围内的多个个体的DNA序列，该项目将揭示它们的种群在过去扩大或减少的程度。这项研究揭示了这些生物如何应对环境变化，以及导致其目前分布模式的过程。该项目将为纽约城市学院的本科生和硕士生提供分子系统方法的培训和指导。 该项目还将通过对巴西北方的联合实地考察促进新的美国-巴西科学合作。该项目旨在测试与森林相关的蜥蜴种群如何受到最近提出的第四纪南美洲水分输送动力学的影响。它将生成亚马逊和大西洋雨林中三种树栖蜥蜴物种的单核苷酸多态性（SNP）数据（Anolis punctatus，A。ortonii和Polychrus marmoratus）。系统发育关系将使用基于聚结的方法进行推断。将进行遗传结构分析，以推断不同物种内有效种群的数量。人口扩张、收缩或持续的情景将根据合并模拟以及基于可能性的方法和近似贝叶斯计算进行评估。人口统计学参数的估计值，如有效人口规模，人口之间的分歧时间和迁移率将使用最佳拟合模型进行估计。这些数据将为巴西大西洋和亚马逊雨林的种群结构以及它们如何应对最近的气候扰动提供新的见解。

Tens of thousands of years ago the levels of rainfall in northeastern South America were much higher than today. As a result, the Amazon and the Atlantic rainforests were much more extensive, occupying regions that are today covered by deserts and savannahs. When the climate became drier, those forests retracted and became fragmented. This change likely had dramatic effects on the animals and plants that live in tropical rainforests. This project asks how tropical forest organisms were affected by the climatic changes experienced over the past 250,000 years. The genomes of three species of lizards that occur in the Brazilian forests will be studied, and by comparing the DNA sequences of multiple individuals per species over their geographic range, the project will uncover the extent that their populations have expanded or declined in the past. This research shed light on how these organisms have responded to environmental change, in addition to the processes that led to their current distribution patterns. This project will provide training in molecular systematic methods and mentorship for undergraduate and Masters students at The City College of New York. It also will foster new USA-Brazil scientific collaborations through joint field trips to northern Brazil.This project seeks to test how populations of forest-associated lizards have been affected by a recently proposed dynamics of moisture transport in South America during the Quaternary. It will generate Single Nucleotide Polymorphism (SNP) data of three arboreal lizard species that occur in both Amazon and the Atlantic rainforests (Anolis punctatus, A. ortonii and Polychrus marmoratus) using a restriction-site associated DNA sequencing protocol. Phylogenetic relationships will be inferred using coalescent-based methods. Analyses of genetic structure will be performed to infer the number of effective populations within the different species. Scenarios of population expansion, contraction, or persistence will be evaluated based on coalescent simulations and both likelihood-based methods and Approximate Bayesian Computation. Estimates of demographic parameters such as effective population sizes, divergence times between populations, and migration rates will be estimated using best-fit models. Together these data will provide new insights on the population structure for taxa in the Brazilian Atlantic and Amazonian rainforests, and how they have responded to recent climate perturbations.