中国及其他分布区域野生虎的系统地理学和遗传起源研究进展
Proceedings in Phylogeography and Genetic Ancestry of Tigers (Panthera tigris) in China and Across Their Range
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摘要: 世界野生虎(Panthera tigris)传统上被划分为8个亚种，其中3个亚种已于20世纪灭绝，而剩余种群的生存仍然受到偷猎、栖息地丧失和片断化的威胁。作为唯一栖息着4个现存虎亚种的国家，中国在世界虎的保护事业中负有重要责任，然而其野生和圈养虎的分类地位却仍然不确定。最近一项研究(Luo et al，2004)从所有现存野生虎分布地区(包括中国)采集了134份“基准样品”(即原产野外或有确定地域起源的个体生物样品)，对虎的系统地理学、种群结构以及遗传起源进行了全面分析。所用的分子标记包括四千碱基对的线粒体DNA、30个核基因组微卫星位点，以及MHCDRB基因。研究结果表明，虽然虎的整体遗传多态性较低，但是种群分化程度很高，它们被划分为6个，而不是5个现存亚种：(1)西伯利亚虎(P. t. altaica)；(2)苏门答腊虎(P. t. sumatrae)；(3)孟加拉虎(P. t. tigris)；(4)华南虎(P. t. amoyensis)；(5)印支虎(P. t. corbetti)；(6)新定义的亚种马来虎，暂命名为P. t. Jacksoni。由于所研究样本量有限，目前暂定的华南虎亚种还需进一步确定。现有华南虎圈养种群包括遗传关系相距较远的两支：一支与印支虎(P. t. corbetti)无异；而另一支则与其他种群均相距甚远，可能代表了真正的华南虎(P. t. amoyensis)。利用分子生物学方法对中国动物园中圈养虎的遗传起源调查亟待进行，以确认该圈养种群整体的遗传独特性或者非独特性。换言之，这将是确认华南虎是否仍然存在的关键。Abstract: Of eight traditionally classified subspecies of the tiger Panthera tigris three have recently gone extinct and poaching, habitat loss and fragmentation continue to threaten its survival. China historically harbors four of the existing subspecies and thus has high conservation priority, yet their status, both in the wild and captivity, remains highly uncertain. A recent molecular survey (Luo et al, 2004) of 134 “voucher specimens” (taken from tigers of verified wild ancestry and geographic origin), from across the full range including China, examined three different types of molecular markers; four kilobase-pairs of mitochondrial DNA, 30 nuclear microsatellite loci and the nuclear major histocompatibility complex class Ⅱ DRB gene; to elucidate the genetic structure of tiger populations. The data revealed relatively low genetic variation but nonetheless significant population subdivisions, suggesting six rather than five living subspecies: (1) Amur tiger P. t. altaica, (2) South China tiger P. t. amoyensis, (3) a refined Indochinese tiger P. t. corbetti, (4) a new subspecies Malayan tiger P. t. jacksoni, named after the tiger conservationist Peter Jackson, (5) Sumatran tiger P. t. sumatrae, and (6) Bengal tiger P. t. tigris. Reduced gene flow and genetic drift in isolated populations since the last genetic diminution about 72 000-108 000 years ago, as well as the recent anthropogenic range contraction, is likely to have caused these partitions. In particular, the proposed South China tiger lineage is tentative due to limited sampling. It is apparent that current captive South China tigers inherit at least two genetic lineages: one that is unique and distinct from the other subspecies and a second indistinguishable from the northern Indochinese tigers. An explicit genetic assessment of the captive tigers in China is urgently needed to validate the uniqueness or nonuniqueness of the South China tiger, or indeed the survival of P. t. amoyensis.
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