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Brett Riddle博士获得了一笔拨款，用于调查北美西南部半岛、索诺兰和奇瓦瓦温暖沙漠中高度干旱适应的小型哺乳动物（口袋鼠、仙人掌鼠、羚羊地松鼠和梅里亚姆袋鼠鼠）的详细生物地理结构。这些小型哺乳动物群体总共代表了20个物种，它们的基因组中包含了一系列事件（包括地理隔离和分散周期）的特征，这些事件记录了地球历史与生物多样化之间的长期历史联系。这些事件包括几百万年前对区域沙漠形成起重要作用的地质构造活动，以及最近200万年（更新世）内的气候变化周期。我们将使用来自1656个标本的线粒体基因组的DNA序列来检验这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干旱哺乳动物生物群的多样化在多大程度上归因于：1)新近纪的代变或分散事件；2)更新世雨—雨间旋回相关事件；或3)更新世后的过滤屏障。我们对小型哺乳动物生物地理历史的分析将为解决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，从而适用于在这些干旱地区表现出类似分布模式和长期适应的其他生物类群。阐明这些源自历史的生物多样化模式和过程，对于在这些日益受到影响和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将是至关重要的。

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.