Collaborative Research: Nested Events and Embedded Phylogeographic Structure within the Southern Regional Deserts of North America

内华达大学拉斯维加斯分校的布雷特·里德尔博士获得了一项拨款，用于研究北美西南部温暖的半岛、索诺兰和奇瓦瓦沙漠中高度干旱适应的小型哺乳动物(口袋鼠、仙人掌鼠、羚羊地鼠和梅里亚姆袋鼠)的详细生物地理结构。这些小型哺乳动物群体代表了总共20个物种，它们的基因组中包含了事件(包括地理隔离和扩散的循环)的特征，这些事件记录了地球历史和生物多样性之间的长期历史联系。这些事件包括有助于几百万年前区域沙漠形成的地质构造活动，以及最近200万年(更新世)内的气候变化周期。我们将使用大约1656个标本的线粒体基因组DNA序列来检查这20个物种中嵌入的进化谱系的地理分布模式，并使用比较分析工具来询问这种Aridland哺乳动物生物群的多样性在多大程度上可归因于：1)新近纪的更替或扩散事件；2)与更新世的暴雨-暴雨间旋回有关的事件；或3)后更新世的过滤屏障。我们对小型哺乳动物生物地理历史的分析将为研究北美南部地区沙漠的进化生物学、生态学和保护生物学提供一个总体框架，因此也适用于其他在这些干旱地区表现出类似分布模式和长期适应的生物种群。阐明这些历史上衍生的生物多样性模式和进程，对于在这些日益受到影响和受到威胁的沙漠地区制定养护管理规划所需的生物多样性的理解至关重要。

A grant has been awarded to Dr. Brett Riddle at the University of Nevada Las Vegas to investigate detailed biogeographic structure in highly arid adapted small mammals (pocket mice, cactus mice, antelope ground squirrels, and Merriam's kangaroo rat) across the Peninsular, Sonoran, and Chihuahuan warm deserts in southwestern North America. These small mammal groups represent a total of 20 species that collectively contain in their genomes a signature of the events (including cycles of geographic isolation and dispersal) that record a long historical association between earth history and biotic diversification. These events include geological tectonic activities instrumental in the origination of regional deserts several millions of years ago, as well as cycles of climatic transformations within the most recent 2 million years (the Pleistocene epoch). We will use DNA sequences from the mitochondrial genome across some 1656 specimens to examine patterns of geographic distribution of evolutionary lineages embedded within these 20 species, and use comparative analytical tools to ask to what extent the diversification of this aridlands mammal biota is attributable to: 1) Neogene vicariant or dispersal events; 2) events associated with pluvial-interpluvial cycles of the Pleistocene; or 3) post-Pleistocene filter-barriers. Our analysis of small mammal biogeographic history will provide a general framework for addressing the evolutionary biology, ecology, and conservation biology of the southern regional deserts of North America and hence be applicable to other biotic groups that demonstrate similar distributional patterns and long-term adaptation within these aridlands. Elucidation of these historically derived patterns and processes of biological diversification will be critical to formulating the understanding of biodiversity required for conservation management planning in these increasingly impacted and threatened desert regions.