Abstract
Eight traditional subspecies of tiger (Panthera tigris), of which three recently became extinct, are commonly recognized on the basis of geographic isolation and morphological characteristics. To investigate the species' evolutionary history and to establish objective methods for subspecies recognition, voucher specimens of blood, skin, hair, and/or skin biopsies from 134 tigers with verified geographic origins or heritage across the whole distribution range were examined for three molecular markers: (1) 4.0 kb of mitochondrial DNA (mtDNA) sequence; (2) allele variation in the nuclear major histocompatibility complex class II DRB gene; and (3) composite nuclear microsatellite genotypes based on 30 loci. Relatively low genetic variation with mtDNA, DRB, and microsatellite loci was found, but significant population subdivision was nonetheless apparent among five living subspecies. In addition, a distinct partition of the Indochinese subspecies P. t. corbetti into northern Indochinese and Malayan Peninsula populations was discovered. Population genetic structure would suggest recognition of six taxonomic units or subspecies: (1) Amur tiger P. t. altaica; (2) northern Indochinese tiger P. t. corbetti; (3) South China tiger P. t. amoyensis; (4) Malayan tiger P. t. jacksoni, named for the tiger conservationist Peter Jackson; (5) Sumatran tiger P. t. sumatrae; and (6) Bengal tiger P. t. tigris. The proposed South China tiger lineage is tentative due to limited sampling. The age of the most recent common ancestor for tiger mtDNA was estimated to be 72,000–108,000 y, relatively younger than some other Panthera species. A combination of population expansions, reduced gene flow, and genetic drift following the last genetic diminution, and the recent anthropogenic range contraction, have led to the distinct genetic partitions. These results provide an explicit basis for subspecies recognition and will lead to the improved management and conservation of these recently isolated but distinct geographic populations of tigers.
Highlights
The tiger (Panthera tigris) is the largest felid species and a widely recognized symbol of wildlife conservation
Phylogenetic Analysis of mitochondrial DNA (mtDNA) and Microsatellites Mitochondrial gene fragments were amplified and sequenced from DNA extracted from 72 blood or tissue specimens using 10 cytoplasmic mitochondria (Cymt)-specific primer pairs (Figure 2 and Table 1)
The position of PCR primers used for amplification of Cymt specific sequences and alignment of the homologous nuclear mitochondrial (Numt) sequence in tiger mitochondria
Summary
The tiger (Panthera tigris) is the largest felid species and a widely recognized symbol of wildlife conservation. Tigers inhabited much of Asia, including the regions between the Caspian and Aral Seas, southeastern Russia, and the Sunda islands (Mazak 1981; Hemmer 1987; Herrington 1987). Since the early 1900s, habitat loss, fragmentation, and human persecution have reduced tiger populations from probably over 100,000 in 1900 to fewer than 7,000 free-ranging individuals (Nowell and Jackson 1996; Dinerstein et al 1997; Kitchener and Dugmore 2000). Most populations consist of less than 120 animals, increasing the risk of local extirpation due to demographic and genetic factors (Smith and McDougal 1991; Dinerstein et al 1997). Sondaica) tiger subspecies were eradicated by the 1940s, 1970s, and 1980s respectively (Nowell and Jackson 1996).
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