Data from: Evolutionary history of Lost World frogs (Ph.D. thesis)

The Lost World of South America is a unique landscape of flattop mountains that are home to hundreds of endemic species. These flattop mountains, or tepuis, were formed after millions of years of erosion of the high-altitude Guiana Shield plateau. The tepui summits, isolated by their surrounding cliffs that can be up to 1000 m tall, are thought of as "islands in the sky," harboring relict flora and fauna that underwent vicariant speciation due to plateau fragmentation. High endemicity atop tepui summits supports the idea of an ancient "Lost World" biota. However, recent work suggests dispersal between lowlands and summits occurred long after tepui formation, but neither view (i.e., ancient vicariance vs. recent dispersal) has strong empirical support owing to a lack of studies. I tested diversification hypotheses of the Guiana Shield highlands by estimating divergence times of Tepuihyla, a Guiana Shield endemic genus. Diversification among the different species did not support the Lost World Hypothesis of summit diversification, but rather recent dispersal approximately 50 million years after tepuis formed. This study was the first to explicitly test these hypotheses with a tepui endemic vertebrate, and as such a significant contribution to our understanding of the evolutionary history of this region. After increasing sampling, I focused on three of the most recently diverged lineages of Tepuihyla, in order to examine population genetics, phylogeography, and species delimitation atop these summits. I found high levels of lineage sorting in spite of low divergences in both nuclear and mitochondrial genes. I also found an unexpected pattern of nuclear versus mitochondrial diversity, suggesting the possibility of a recent mitochondrial selective sweep. Species delimitation analyses support the existence of a cryptic, undescribed summit species. Finally, I obtained a Single Nucleotide Polymorphism matrix with next-generation sequencing in order to observe more fine-scale population structure atop the Chimantá massif, a formation composed of ten tepui summits and intermediate altitudes separating them. I found high levels of population structure and assignment atop different tepui summits on the massif, indicating that even at extremely low levels of divergence the landscape complexity may be fomenting population isolation even at the smaller scale of within-massif divergences.

南美洲失落世界是一片独特的平顶山地景观，栖息着数百种特有物种。这些平顶山，即特普伊（tepui）山，由圭亚那地盾（Guiana Shield）高海拔高原经数百万年侵蚀形成。被高达1000米的峭壁环绕隔绝的特普伊山顶，被称为“天空中的岛屿”，孕育着因高原碎片化而经历异域成种（vicariant speciation）的孑遗动植物类群。特普伊山顶极高的特有物种丰富度，支撑了“失落世界”古生物群落的假说。然而，近期研究表明低地与山顶间的物种扩散发生在特普伊山形成许久之后，但由于相关研究匮乏，这两种观点（即古代异域分化与近期扩散）均缺乏强有力的实证支撑。本研究以圭亚那地盾特有属特普伊蛙属（Tepuihyla）的分化时间为切入点，检验了圭亚那高地的物种分化假说。不同物种间的分化模式并不支持山顶物种分化的“失落世界假说”，而是支持在特普伊山形成约5000万年后发生的近期扩散事件。本研究首次以特普伊特有脊椎动物为研究对象，对上述假说开展了明确检验，因此为我们理解该区域的演化历史作出了重要贡献。在扩大采样规模后，本研究聚焦于特普伊蛙属中三个分化最晚的支系，以解析这些山顶的种群遗传学、系统地理学及物种界定问题。研究发现，尽管核基因与线粒体基因的分化程度均较低，但支系分选程度较高。同时还观测到核基因与线粒体多样性间的异常模式，提示存在近期线粒体选择性清除事件的可能性。物种界定分析结果支持存在一种未被描述的隐秘山顶物种。最后，本研究借助下一代测序技术构建了单核苷酸多态性（Single Nucleotide Polymorphism, SNP）矩阵，以解析钦塔马地块（Chimantá massif）山顶的精细种群结构——该地块由10座特普伊山顶及分隔它们的中等海拔区域共同组成。研究发现该地块内不同特普伊山顶间存在显著的种群结构与遗传组分分化，这表明即便在极低的分化水平下，景观复杂性也可在地块内部的小尺度范围内促进种群隔离。