中国科学院昆明动物研究所机构知识库

在尼日利亚，由于不充足的调查和研究手段的限制，我们对该地区两栖爬行物种（两爬物种）的多样性和地理分布信息的认知还很局限。加沙卡古姆蒂国家公园（Gashaka Gumti National Park）是尼日利亚最大的国家公园，拥有不同的栖息地和多样的景观。然而，关于该国家公园的两爬物种多样性和分布的详细信息仍然鲜为人知。因此，本着上述背景，我们对加沙卡古姆蒂国家公园的两爬物种开展了调查。此外，尼日利亚两爬物种的鉴定往往依赖于外部形态特征。在本研究中，我们结合形态学方法和分子数据（16S 核糖体RNA）进行物种鉴定。从整体的多样性评估中，我们选取了彩虹飞蜥 (学名:Agama agama) 作为进一步生物地理学研究的目标物种，基于分子遗传数据，我们研究了彩虹飞蜥的多样性演化历程及影响因素。最后，我们探讨了西非（West Africa）飞蜥属（主要集中在尼日利亚）的进化关系。第一章：总体概述了研究背景，介绍尼日利亚的地理地形和生态环境，加沙卡古姆蒂国家公园的介绍，目前的研究现状和存在的问题，研究目标和科学问题。第二章：综述了相关文献。这一章节全面回顾了两爬区系的生物学特征，两爬物种在生态系统中的作用，两爬物种的多样性和地理分布，两爬物种的栖息地偏好，对两爬物种存在的威胁，两爬物种的保护以及以两爬物种为代表的系统地理研究。第三章：重点研究对尼日利亚加沙卡古姆蒂国家公园的两爬物种的多样性评估和DNA条形码工作。为了建立该国家公园的两爬物种的多样性清单，我们在2016年8月对该国家公园进行了两爬物种的调查，在此次调查中，共收集到259个标本，包括15个两栖物种和15个爬行物种。本研究揭示16S 核糖体RNA（16S rRNA）基因在尼日利亚两爬物种鉴定中的实用性。系统发育结果显示彩虹飞蜥 (学名: Agama agama) 内部存在隐存多样性。这项研究强调了建立全面的DNA条形码参考数据库的重要性，这样会大大便利研究尼日利亚两爬物种的多样性。第四章：在大的生态-地理框架下，重点研究了尼日利亚彩虹飞蜥(学名:Agama agama)的系统地理学。尼日利亚存在多种多样的生态环境，这为探讨地理和生态变化对脊椎动物多样性分化的影响提供了很好的场所。彩虹飞蜥(学名: A. agama) 生活在多样的栖息地，因此，该物种可能会存在高的遗传分化和多样性。基于上述背景，我们提出的假说是：在尼日利亚不同地理区域的广泛采样，将会揭示彩虹飞蜥的地理分化和多样化模式。为了检验这些假设，我们重建了该物种的母系进化，系统发育结构，研究了该物种的群体遗传学和分歧时间估算。线粒体DNA（mtDNA）和串联基因标记（核基因+mtDNA）的系统发育结果都显示彩虹飞蜥存在四个明显的支系。结果清楚地表明该物种的遗传结构与生态地理区域（eco-geographic regions）的分化是一致的。时间估算结果显示不同支系的分化时间与更新世气候波动吻合，这很可能导致了气候介导的栖息地变化。因此，环境的异质性深刻影响了物种的遗传结构。目前，由于近来栖息地的片段化，特别是在尼日利亚西部，该物种面临生存上的威胁。加大尼日利亚物种保护工作的力度是必要的。第五章：重点关注飞蜥属(Agama)的进化关系研究。鉴于对尼日利亚的爬虫学研究很少，我们对在西非（West Africa）范围内的尼日利亚飞蜥属(Agama)的系统发育结构的了解还不清楚，这限制了对西非飞蜥属完整演化的理解。因此，我们收集了尼日利亚境内飞蜥属的112个标本。基于线粒体DNA（16S 核糖体RNA）的分析推断了该属的系统发育关系。我们的结果发现了在尼日利亚东北部存在一个新的支系。此外，结果表明，尼日利亚飞蜥属物种与喀麦隆和尼日尔的关系最密切。这表明几内亚森林（Guinean forest）很可能是扩散和分化的重要生物地理走廊。在此过程中，我们还首次在尼日利亚发现了物种Agama parafricana。通过与其他国家物种的比较，我们描述了该物种的形态变异。

Insufficient herpetological studies have limited knowledge on diversity and distribution of amphibians and reptiles (collectively referred to as herpetofauna) in Nigeria. Gashaka Gumti National Park (GGNP) is the largest national park in Nigeria with diverse habitats and varying landscapes. However, detailed information on the diversity and distribution of herpetofauna in this park remains poorly known. Hence, I carried out preliminary survey to examine the diversity and distribution of herpetofauna in the park. Furthermore, species identification of Nigerian herpetofauna has often relied on the use of external features in identification. In this study, I used combined morphological method and molecular data (16S ribosomal RNA) in species identification. From the preliminary herpetological diversity assessment, I selected Agama agama as a species of interest for further biogeographic studies. Herein, I used molecular data to examine processes that govern diversification of Nigerian A. agama. Further, I examined the evolutionary relationships of Nigerian Agama within the West African Agama radiation. Chapter one gives an overview of the background of the study, geography of Nigeria, description of the study area (GGNP), problem statement and justification for the study, aim and objectives of the study and research questions that would guide the study. Chapter two is the review of related literatures. This chapter gives a comprehensive review of the biology of herpetofauna, roles of herpetofauna in the ecosystem, diversity, distribution and abundance of herpetofauna, habitat preferences for herpetofauna, threats to herpetofauna, conservation and the use of herpetofauna in phylogeographic studies. Chapter three focuses on the biodiversity assessment and DNA barcoding of amphibians and reptiles of Gashaka Gumti National Park, Nigeria. Thus, to create an inventory on the diversity and distribution of herpetofauna in the park, a herpetological survey of the park was conducted in August 2016. A total of 259 individuals comprising 15 amphibian and 15 reptilian species were collected. This study shows the usefulness of 16S ribosomal RNA sequences in the identification of Nigerian species. A neighbor-joining tree displays cryptic divergent lineages within Agama agama. This study underscores the importance of establishing a comprehensive barcode reference library for efficiently studying the diversity of Nigerian amphibians and reptiles. Chapter four focuses on Nigerian red headed rock agama Agama agama but in a wide eco-geographic context. Nigeria offers unique opportunities for exploring the effects of geographic and ecological variation on the diversification of vertebrate lineages. The red headed rock agama, A. agama, lives in a wide range of habitats and, thus, might be expected to show a genetic structuring and diversification. Therefore, I hypothesized that extensive sampling of A. agama across Nigerian eco-geographic zones will reveal geographic divergence and patterns of diversification. To test these hypotheses, I inferred the matrilineal genealogy, phylogeny, population genetics, historical demography and divergence times. The Bayesian phylogenetic analyses of mitochondrial DNA (mtDNA) and concatenated (nuclear and mtDNA) gene markers recovers four well-supported lineages. Strong evidence of genetic structuring is consistent with eco-geographic regions. The estimated dates of separation among lineages coincide with Pleistocene climate fluctuations, which probably led to habitat changes associated with climate. Thus, environmental heterogeneity impacts the genetic structure. This species might be facing threats due to recent habitat fragmentation especially in western Nigeria. Conservation efforts appear to be necessary in Nigeria. Chapter five focuses on the genus Agama. Given the dearth of herpetological studies in Nigeria, knowledge on the matrilineal affinities of Nigerian Agama within the West African (WA) radiation are unknown. This limits a complete understanding of WA Agama radiation. Thus, I collected 112 specimens belonging to genus Agama across Nigeria. Analyses of mitochondrial DNA (16S ribosomal RNA sequences) inferred the matrilineal relationships of all the currently recognized Nigerian species of Agama within the WA radiation. The result of the genealogical analysis adds a new matrilineal lineage from north-eastern Nigeria to WA radiation. Further, the result shows that Nigerian Agama has closest relationship with Cameroon and Niger. This indicates that the Guinean forest may be a biogeographic corridor for dispersal and diversification. The field collections from Nigeria also document for the first time the presence of Agama parafricana from the montane savannah region of GGNP, eastern Nigeria. Accordingly, I described the morphological variation and compared with specimens from other countries.