【摘要】 黒眶蟾蜍Bufo melanostictus(Anura,Bufonidae)是亚洲常见的蟾蜍,广泛分布于中国华南地区。由于华南地区分布着众多的大陆架岛屿及其地貌的复杂性与多样性,因而不同地区的黑眶蟾蜍种群可能存在地理上的遗传变异。本文首次采用DNA序列分析方法,检测了采自我国华南6个省市地区(福建、广东、广西、海南、香港、台湾),包括4个主要大陆架岛屿(海南岛、大屿山、南澳岛、台湾岛)的12个黑眶蟾蜍种群共84个个体,获得mtDNA控制区序列长956bp的片段,共有75个变异位点(26.3%为单个多态位点,73.7%为简约信息位点),12个插入/缺失。所获得的44个单倍型中有5个为种群间共享的单倍型。华南地区黒眶蟾蜍较高的的遗传多样性(单倍型多样性h=0.977)不但表现为海岛种群内普遍具有较高的遗传变异,而且遗传分化指数(FST)、基因流(Nm)、Amova和Samova等分析均表明种群之间已经发生了明显的遗传分化。从Amova分析和分子系统发育分析结果来看,华南地区分布于大陆与分布于海岛的种群之间并未发生明显的遗传分化,说明由陆缘浅海造成的阻隔作用(isolation by barrier)并不能很好地解释华南地区黑眶蟾蜍种群之间遗传分化的原因。遗传距离与地理距离的低度相关(Mantel测试R=0.192,P<0.001)说明华南地区黑眶蟾蜍的种群分化並不完全符合距离决定分化(isolation by distance)的假说。Samova的结果表明华南沿海大陆东部的3个种群(广东汕头、福建莆田和东山)与其它地区9个种群之间的变异最大(FCT=0.35097),因此,推测黑眶蟾蜍这2个地理区域组之间应该存在着其它地理隔离屏障,对两地黑眶蟾蜍的迁移有一定的阻隔作用,产生此隔离效应的天然地理屏障可能为莲花山脉。黑眶蟾蜍种群在历史上曾发生多次局部扩张,时间大约在距今0.025MYA左右,这与最后一次冰期结束的时间相吻合,而位于我国华南大陆周边的4个主要大陆架岛屿(海南岛、大屿山、南澳岛、台湾岛)可能是华南地区黒眶蟾蜍在第四纪冰期的"避难所"。南澳岛种群所存在的特殊单倍型验证了这一岛屿避难所的存在。本研究揭示的地理种群之间的遗传变异和分化,对进一步了解华南地区乃至亚洲的黒眶蟾蜍的生物地理关系有重要意义。更多还原

【Abstract】 Bufo melanostictus (Anura,Bufonidae) is known as the "Asiatic Common Toad",a widespread species in South China. The diverse topography of this region,with numerous continental shelf islands,provides an opportunity for considerable geographic variation. We studied for the first time the genetic diversity using mitochondrial DNA in the control region (mtDNA D-loop). Samples consist of 12 populations with 84 individuals from 6 provincial regions (Fujian,Guangdong,Guangxi,Hainan,Hong Kong,Taiwan) that include 4 major islands (Hainan,Lantau,Nan Ao,Taiwan) in South China. In the nucleotide sequence of 956 base pairs there were 75 variable sites (26.3 % singleton polymorphic and 73.7 % parsom-inform polymorphic sites) with 12 insertions and deletions. Among 44 haplotypes identified,only 5 were shared among populations. High genetic diversity (h=0.977) not only existed within populations on islands,but also among different geographic regions. Amova and phylogenetic analyses (Neighbor Joining and Baysian) of mtDNA haplotypes showed insignificant genetic divergence between island and proximate mainland populations,indicating that post-glacial sea level rise that separated the islands from the mainland was not effective as an isolation barrier. However,Samova revealed significant differences among populations between eastern and western South China,where the largest geographic variation occurred (FCT=0.35097) if all populations were divided into the eastern coastal group (3 populations:ST of Guangdong,PT and DS of Fujian) and the rest of the 9 populations. This result and the Mantel test (R=0.192,P<0.001) both confirmed that the significant geographic variation between these 2 groups contradicts the hypothesis that the genetic variation was due to isolation by distance. We suspect that the divergence mechanism may involve other geographic barriers such as the Lianhua Mountain Range,which lies between the eastern coastal and western populations. Bufo melanostictus went through several local population expansions at about 0.025 MYA; these events were coincident with the last glacial maximum (at about 0.018MYA). A unique haplotypes from Nan Ao Island provides evidence that continental shelf islands in South China may have served as genetic refuges during Quaternary interglacials. Our results contribute to the understanding of paleontology and biogeography of Bufo melanostictus in South China.更多还原