When is an extinct subspecies not extinct? Maybe when it is not really a subspecies at all— The tiger subspecies Panthera tigris virgata, or Caspeian Tiger, was purported to have become extinct in February of 1970 when the last survivor was shot in Turkey. Leaving aside the hard to grasp idea that we might know down to the month when a species became extinct because someone shot the last one, it is clear that one tiger can hardly make little tigers by itself, so that subspecies was already doomed. Or was it?
In a paper published in January, a group of researchers used mitochondrial DNA (mtDNA) haplotype analysis to show that what is currently defined as two subspecies ( P. t. virgata [Caspian] and P. t. altaica [Amur or Siberian]) might more correctly be categorized as one (1). The authors created composite mtDNA haplotypes for the Caspian Tiger using samples from twenty wild Caspian tigers found in museum collections, and found that the Caspian Tigers had a major mtDNA haplotype that differed from the monomorphic haplotype of the Amur tiger by only one nucleotide. Combined molecular, phylogenetic and geographical analysis gives strong support to the hypothesis that P.t. virgata and P.t. altaica are taxonomically the same subspecies.
Although the label of “extinct” might have been premature for the Caspian Tiger, its resurrection might be bitter sweet. The Amur (or Amur/Caspian) Tiger hovers dangerously close to that label itself, and a large genetic survey of the wild population estimated that the ~500 individuals living in the wild equate to only about 35 breeding individuals in terms of genetic diversity (2). The “Caspian” Tiger might be back from the dead, but its future is uncertain, and its best hope probably rests with the reservoir of genetic diversity that has been carefully maintained in the captive tiger populations.
- Driscoll CA, Yamaguchi N, Bar-Gal GK, Roca AL, Luo S, Macdonald DW, & O’Brien SJ (2009). Mitochondrial phylogeography illuminates the origin of the extinct caspian tiger and its relationship to the amur tiger. PloS one, 4 (1) PMID: 19142238
- Henry P, Miquelle D, Sugimoto T, McCullough DR, Caccone A, & Russello MA (2009). In situ population structure and ex situ representation of the endangered Amur tiger. Molecular ecology, 18 (15), 3173-84 PMID: 19555412
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