Following Linnaeus's first descriptions of the species, several tiger specimens were described and proposed as subspecies. The validity of several tiger subspecies was questioned in 1999. Most putative subspecies described in the 19th and 20th centuries were distinguished on basis of fur length and colouration, striping patterns and body size, hence characteristics that vary widely within populations. Morphologically, tigers from different regions vary little, and gene flow between populations in those regions is considered to have been possible during the Pleistocene. Therefore, it was proposed to recognize only two tiger subspecies as valid, namely P. t. tigris in mainland Asia, and P. t. sondaica in the Greater Sunda Islands.
Results of craniological analysis of 111 tiger skulls from Southeast Asian range countries indicate that Sumatran tiger skulls differ from Indochinese and Javan tiger skulls, whereas Bali tiger skulls are similar in size to Javan tiger skulls. The authors proposed to classify the Sumatran and Javan tigers as distinct species, P. sumatrae and P. sondaica, with the Bali tiger as subspecies P. sondaica balica.
In 2015, morphological, ecological, and molecular traits of all putative tiger subspecies were analysed in a combined approach. Results support distinction of the two evolutionary groups continental and Sunda tigers. The authors proposed recognition of only two subspecies, namely P. t. tigris comprising the Bengal, Malayan, Indochinese, South Chinese, Siberian and Caspian tiger populations, and P. t. sondaica comprising the Javan, Bali and Sumatran tiger populations. The authors also noted that this reclassification will affect tiger conservation management. The nominate subspecies P. t. tigris constitutes two clades:
a northern clade composed of the Siberian and Caspian tiger populations
a southern clade composed of all other mainland populations.
One conservation specialist welcomed this proposal as it would make captive breeding programmes and future rewilding of zoo-born tigers easier. One geneticist was sceptical of this study and maintained that the currently recognised nine subspecies can be distinguished genetically.
In 2017, the Cat Classification Task Force of the IUCN Cat Specialist Group revised felid taxonomy and recognized the tiger populations in continental Asia as P. t. tigris, and those in the Sunda Islands as P. t. sondaica. This two-subspecies view has been largely rejected by researchers. Results of a 2018 whole-genome sequencing of 32 specimens support six monophyletic tiger clades corresponding with the living subspecies and indicate that the most recent common ancestor lived about 110,000 years ago. The following tables are based on the classification of the species Panthera tigris provided in Mammal Species of the World. It also reflects the classification used by the Cat Classification Task Force in 2017
Loading contexts...
