Seven of nine tiger subspecies should be eliminated, advises a new paper that could radically change the way that not only tigers, but also other animals, are classified.
If the proposed changes, outlined in the latest issue of Science Advances, are implemented, the world's tigers would only fall into two subspecies: the Sunda tiger and the continental tiger. These subspecies would no longer be recognized: Bengal tiger, Caspian tiger, Amur tiger, Javan tiger, South Chinese tiger, Balinese tiger, Sumatran tiger, Indochinese tiger and Malayan tiger.
"A classification into too many subspecies - with weak or even no scientific support - reduces the scope of action for breeding and rehabilitation programs," lead author Andreas Wilting told Discovery News. "For example, tiger populations in South China and Indochina have been reduced to such low numbers that, if each continues to be classified as separate subspecies, they would likely face extinction."
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By combining these and other "continental" tigers into one subspecies, he argues they can be "managed as a single conservation unit."
The situation is dire, as fewer than 4000 tigers inhabit the forests of Asia. The big cats occupy only 7 percent of their estimated former distribution range. Habitat loss and degradation, as well as hunting by humans, are the primary threats to tigers now.
Wilting explained, "There is still a very high demand for various products from wild tigers, particularly in Eastern Asia."
For the study, Wilting and an international team of researchers compared the form and structure of more than 200 tiger skulls, as well as the coloration and stripe patterns of more than 100 tiger skins with molecular genetic data, ecological and life history traits.
The comparisons found that there is tremendous overlap between the existing nine subspecies. Tigers from the three Sunda islands - Sumatra, Java and Bali - were, however, different enough from continental tigers to warrant their classification into a separate subspecies.
Right now subspecies are largely defined by a population's primary geographic region, which is why their locations are in their subspecies names, from Bengal to Malayan.
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"The problem with using the geographical distribution is that it is arbitrary where to draw the lines, particularly on continuous habitats such as continental Asia," Wilting said, explaining that no clear geographical barriers have existed over the past ten thousand or more years for mainland Asian tigers.
The taxonomic status of all living wild cats is now being revised by a working group of the IUCN/SSC Cat Specialist Group. The co-chairs of that are Urs Breitenmoser and his wife Christine Breitenmoser-Würsten.
While the Breitenmosers suggest that more research is needed on tigers before a decision is made on the proposed changing of subspecies, they told Discovery News that "the practical consequences for conservation could be that the reduction of subspecies in tigers could considerably ease translocation and therefore the recolonization."
They explained that re-introducing tigers into their known native habitats is just one of many conservation tools that are being considered.
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They believe that the new paper is "extremely interesting with regards to its possible practical consequences, and is a model case for future reevaluation of the phylogenetic (evolutionary history) status of widely distributed species."
Wilting echoed that the new approach could likely be applied to animals other than tigers.
"We are certain that for many other species, the current taxonomy is invalid," he said. "Most species and subspecies were described hundreds or decades ago, mainly based on a low number of available specimens."