Clouded leopards and the species problem

by Greg Mayer

Alert WEIT-blog reader Dominic has drawn my attention to a not yet published study of clouded leopards, that I’d seen mentioned by the BBC, but I had not seen the actual paper (well, actually, nobody has seen the actual paper— more below on this).

There are two issues here, both of which we’ve considered before here at WEIT. First is the species concept issue, which both Jerry and I mentioned recently (links to Jerry’s posts in mine). The second is a scientific nomenclature issue, one that arose in the infamous Darwinius case.

The species concept issue also comes in two parts. First, are the mainland clouded leopard (Neofelis nebulosa) and the insular clouded leopard (Neofelis diardi) distinct species? And, second, among the insular clouded leopards, are the Bornean and Sumatran populations distinct? The first issue was the focus of two papers in 2006 which raised the insular leopards to full species status. Normally, the raising of insular forms to full species status on the basis of being different from the mainland form raises a warning flag for me, but there is an additional consideration which I think in this case supports the raising to full species status. This is that the islands of Borneo and Sumatra are on the Sunda Shelf, and thus were connected to the mainland as recently as about 10,000 years ago (see Harold Voris’s superb series of paleo-bathymetric maps of the Sunda Shelf for details). So, the insular and mainland forms were in contact very recently, and one good explanation for why this contact would not have led to an erosion of the genetic differences between them is that they were reproductively isolated (i.e., different species). There are other possible interpretations, but the recent contact combined with observed differences certainly makes the 2-species taxonomy reasonable.

The new, unpublished, paper argues not for a new species, but for dividing the insular form into two subspecies, one from Borneo and one from Sumatra. (A subspecies is recognized when there is a particular pattern of geographic variation within a species, namely that there is a geographic segment of the species’ range within which individuals can be distinguished from individuals from other parts of the range. Basically, if you can tell where an individual is from by the way it looks, or, if you tell me where the individual is from, I can tell you what it looks like, then you can name a subspecies.) This seems perfectly reasonable to me.

The problem is that they describe a new subspecies in the paper (rather than reviving a previously described one), but they have also posted a pre-print online and allowed press coverage. Online posting does not constitute publication in the formal sense, and their paper will soon be published on paper. But by generating press coverage (the BBC has included the new name in its coverage) and posting online, they increase the chance that the name will be formally published before their paper appears in print, either accidentally, or on purpose by an unscrupulous individual wanting to steal credit for their work (it does happen). This was part of the problem with Darwinius: the name Darwinius was bandied about before the name was published.

The authors are actually compounding a problem they created for themselves earlier: they published the new name in 2007 (I have not seen this paper), but now consider their proposal at the time nomenclaturally defective, and the name not nomenclaturally available from that publication. (The technical term for what they now regard their 2007 effort is a nomen nudum: a nude name, i.e. a name without a proper description accompanying it, and thus not available for use as a scientific name). The nomenclature of this name could be confused. I hope their paper appears soon.

One thing highlighted by this paper that I want to unreservedly endorse is the use of camera traps for the study of elusive large mammals. These traps have helped with studies of a number of species, including several big cats: jaguars (including Arizona jaguars), Saharan cheetahs, Asiatic cheetahs, tigers, as well as clouded leopards. The BBC, NYT, and other media often highlight the results of these studies. Recently, camera traps revealed an unexpected high-altitude population of tigers in Bhutan, in a valley where three big cats– leopard, snow leopard, and tiger– all live together.

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Buckley-Beason, V.A. et al. 2006. Molecular evidence for species-level distinctions in clouded leopards. Current Biology 16:2371-2376. (pdf)

Kitchener, A.C., M.A. Beaumont, and D. Richardson. 2006. Geographical variation in the clouded leopard, Neofelis nebulosa, reveals two species. Current Biology 16:2377-2383. (pdf)

Wilting, A., V.A. Buckley-Beason, H. Feldhaar, J. Gadau,  S.J. O’Brien, and K.E. Linsenmair. 2007. Clouded leopard phylogeny revisited: support for species recognition and population division between Borneo and Sumatra. Front. Zool. 4:15. (not seen)

Wilting, A., P. Christiansen, A.C. Kitchener, Y.J.M. Kemp, L. Ambu, and J.Fickel. 2011. Geographical variation in and evolutionary history of the Sunda clouded leopard (Neofelis diardi) (Mammalia: Carnivora: Felidae) with the description of a new subspecies from Borneo. Molecular Phylogenetics and Evolution in press. (pdf)