| 其他摘要 | 中国西南山地是世界上地形、地貌最为复杂，生物多样性最为丰富的地区之一。这一区域的山地环境一方面为复杂水系所分割，但另一方面南北走向的横断山脉和环绕四川盆地的山脉将整个区域联系为一整体。特殊的地质历史和地形、地貌对该区域动植物区系和生物多样性造成了深远的影响。亚洲鼩鼹(Uropsilus, Uropsilinae, Talpidae)是鼩鼹亚科唯一的现生类群，也是鼹科现生类群中最原始的一支。该类群是中国西南山地特有的小型兽类，其分类学问题因种间形态极为保守而长期存在争议，但目前尚无任何系统演化方面的研究为系统分类提供证据。有关中国西南山地生物多样性的起源和古老类群的遗存有过多种假说。本研究中，我们尝试以亚洲鼩鼹为模式类群，通过系统进化与系统地理方法探讨中国西南山地物种的多样性及其形成机制，进而在掌握演化过程的基础上厘清这一类群的物种多样性与分类学问题，并为中国西南山地特有类群的生物多样性的发生机制与保护提供参考。本研究首先着眼于亚洲鼩鼹的系统进化。通过对该类群不同物种、同物异名或曾作为亚种的模式产地，以及特殊的动物地理单元进行针对性采样，扩增了56号亚洲鼩鼹标本的10个基因片段，获得了~1,985 bp的线粒体序列和~4,345 bp的核基因序列。研究利用线粒体和核基因序列重建了亚洲鼩鼹类群的系统进化关系，通过化石校正点和“松散”分子钟推算物种的分化时间，并利用基于溯祖理论的物种界定和物种树重建评估了该类群的物种数目和系统发育关系。我们发现，尽管研究使用的56号标本在现有分类系统中只能被鉴定为3个物种，但它们在基因树中却聚成10个拥有极高支持率的单系群，而物种界定和物种树重建则认为其中存在8个物种。根据分歧时间推算的结果，研究认为亚洲鼩鼹的物种分化与晚中新世以来的全球气候变化及青藏高原的数次剧烈隆升有关。这些证据表明亚洲鼩鼹中有数个隐存种，且目前的分类系统严重低估了亚洲鼩鼹的物种多样性。被界定出的8个物种中，拥有长吻鼩鼹(U. gracilis)齿式的标本实际上是由5个候选物种组成的多系群。其中，在目前的分类系统中被作为长吻鼩鼹同物异名的atronates和nivatus均可以被认定为有效种。另外，还有3个未证实的候选物种(U. sp. 1–3)需要更多的证据对其分类地位进行确认。亚洲鼩鼹的系统进化研究一方面提示了现有的分类系统还远没有反映这一类群的物种多样性，需要在了解它们的演化过程后进行分类整理；另一方面，提示我们要从保护遗传的角度尽快予以更多的关注。通过对亚洲鼩鼹的系统地理学研究，我们进一步探索了该类群的演化过程和谱系分布格局。在系统进化研究的标本基础上，扩增了整个亚洲鼩鼹分布区内34个种群的186号组织样品，1,140 bp的线粒体CYT B基因和~4,535 bp的6个核基因片段(BRCA2, GHR, RAG1, RAG2, PLCB4, TTN)。除了系统地理研究常用的系统发育树构建、分化时间推算和群体遗传分析，我们利用溯祖的物种界定方法确定了谱系的分化程度，利用连续扩散模型和生态位模型回顾了亚洲鼩鼹的历史分布动态，并使用亚洲鼩鼹的稳定分布区和遗传网络构建了其在中国西南山地的空间遗传关系。系统发育树的拓扑结构支持之前系统进化研究的结论，且进一步检测到了多达15个独立的进化谱系，而这些谱系的在物种界定中均被认为已达到物种水平的分化。此外，亚洲鼩鼹谱系的分布呈现非常明显的地理结构。历史分布动态的结果显示，亚洲鼩鼹在早更新世就到达现今分布范围的全部区域，而更新世末期剧烈的气候波动并没有使其分布区发生明显的移动；同时中性检验也表明绝大部分谱系在气候变化中比较稳定。这一系列的证据表明亚洲鼩鼹的多样性机制符合“长期稳定(Long-term stable, LS)”模型，复杂地质历史造就的复杂地形促进了迁移能力较弱、偏好中高海拔林下生境的亚洲鼩鼹的隔离与分化，而长期稳定的生境条件一方面有利于亚洲鼩鼹遗传多样性的保存，另一方面则形成了稳定的环境选择，使得不同的物种在形态上变得十分保守。根据亚洲鼩鼹系统演化和系统地理研究的结论，亚洲鼩鼹类群中存在现有分类系统未收录的数个有效物种。最后，通过对保存于中国科学院昆明动物研究所和四川省林业科学研究院的281号亚洲鼩鼹标本的外形及头骨量度进行测量，并利用32个头骨量度进行主成分分析，我们重新整理了亚洲鼩鼹的分类系统，除了再次确认目前分类系统中的5个有效种（少齿鼩鼹U. soricipes、峨眉鼩鼹U. andersoni、长吻鼩鼹U. gracilis、贡山鼩鼹U. investigator和等齿鼩鼹U. aequodonenia）的分类地位，我们还恢复了栗背鼩鼹(U. atronates)和雪山鼩鼹(U. nivatus)的物种地位，另外命名并描记了6个新物种——壮鼩鼹(U. robustus sp. nov)、秦岭鼩鼹(U. qinlingensis sp. nov)、武陵鼩鼹(U. wulingensis sp. nov.)、宾川鼩鼹(U. binchuanensis sp. nov.)、景东鼩鼹(U. jingdongensis sp. nov.)和小鼩鼹(U. parva sp. nov.)，明确了亚洲鼩鼹类群在中国西南山地分布有13个物种。本研究以中国西南山地特有分布的亚洲鼩鼹类群为研究对象，通过分子系统发育研究揭示了该类群的隐存多样性，通过系统地理研究揭示了该类群的多样化过程和机制，最后通过分类系统整理描记并命名了新的亚洲鼩鼹物种。整个研究在整合分类学的框架下完成，不仅关注系统演化的结果，还关注系统演化的过程。亚洲鼩鼹多样性的整合研究同时提示了中国西南山地的物种多样性远超目前的认识，特别是迁移扩散能力较弱、生态幅较窄的类群的多样性需要在未来更多地使用整合分类学手段进行探索。亚洲鼩鼹大量隐存物种的形成既离不开中国西南山地复杂的地形、地貌在气侯变化时期提供了相对稳定的生态环境，也离不开这一类群长期对中高海拔林下温凉、潮湿生境的偏好。相似的生物多样性格局与过程应该广泛存在于这一区域的小型兽类和生态幅较窄、扩散能力较弱的其他类群中。; Mountains of Southwest China (MSC) harbors extremely complex landforms with high biodiversity, and this was hypothesized as glacial refugia and dispersal corridors for a long time. Mountains are cut by drainage systems and lowlands while connecting as an ensemble, the MSC influenced highly in the diversity of fauna and flora endemic to southwest China. The Asiatic shrew moles (genus Uropsilus, Talpidae) comprises a group of terrestrial, montane mammal, endemic to the MSC. These animals are the most primitive living talpids. The taxonomy of Uropsilus has been primarily based on cursory morphological comparisons, and the evolutionary affinities are very little known. In this thesis, we had reconstructed the phylogeny as well as the phylogeographic process of this taxa to explore the species diversity and diversification mechanism.Firstly, to provide insight on the systematics of Uropsilus, the first multi-locus phylogeny and species delimitation has been conducted, including taxon sampling throughout their distribution range. Two mitochondrial genes (~1,985 bp) and eight nuclear genes (~4,345 bp) were obtained from 56 specimens. Ten distinct evolutionary lineages were recovered from the three recognized species, eight of which were recognized as species/candidate species. Five of these putative species were found to be masquerading as the gracile shrew mole (U. gracilis). The divergence time estimation result indicated that globally climate change since the last Miocene and the uplift of the Himalayas may have resulted in the diversification and speciation of Uropsilus. The cryptic diversity found here indicates that the number of species was strongly underestimated under the current taxonomy. Two synonyms of gracilis (atronates and nivatus) should be given full species status, and the taxonomic status of another three candidate species should be evaluated using extensive taxon sampling, comprehensive morphological, and morphometric approaches.Then, the phylogeograohic process and patterns of Uropsilus was examined using 1,140 bp mitochondrial and ~4,535 bp nuclear genes of 186 individuals from 34 population. Genetic structure was strongly congruent with mountain ranges, and total 15 independent lineages were well supported. Continuous-diffusion model and ecological niche model were adopted to reconstruct historical dispersal and distribution trends of Uropsilus. The results revealed Uropsilus was entirely arrived their current distribution range at the early Pleistocene, and there was nearly no range shifts for Uropsilus even in the last glacial cycle. The dispersal distances among Uropsilus populations on basis of stable habitats have good correlation with their genetic distances, which indicated the existence of potential corridors. Neutral tests revealed most of lineages had not experienced population contraction and/or expansion. Species delimitation result shows all 15 lineages should be taken as species.The morphometric of external and cranial measurements of 281 specimens collected by Kunming Institute of Zoology, Chinese Academy of Sciences and Sichuan Academy of Forestry were analyzed using statistical methods on the basis of the conclusions of phylogenetic and phylogeographic study of Uropsilus. Taxonomy of Uropsilus has been revised, six new species were nominated and described. Consequently, we conclude 13 species of Uropsilus, and the conservation status of Uropsilus spp. should also be re-evaluated, as most of the species have very limited distribution.The integrative study of phylogeny, phylogeography and taxonomy intensively devoted to the exploration of species diversity of the Asiatic shrew moles. Such practice could provide a desirable example in studying endemic biodiversity of MSC, as similar driving forces of diversification have probably influenced small mammals which share habitats with Uropsilus. To sum up, the biodiversity of sedentary animals of MSC required urgent scientific attention and conservation. |
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