Whether you consider it as a species, a subspecies or a mere colour variant is largely to do with how one defines species. Phylogenetically, the answer is clear, and represented in the mtDNA tree above (from Wüster et al., 2002) - the Aruba Island rattler is a cumanensis that shrank and faded in the wash.



However, some would regard it as a subspecies due to morphological differences (faded pattern, smaller size), and some would regard it as a full species, on the basis that these differences make it diagnosable from other durissus - just as some authors would regard C.v. caliginis as a separate species on these grounds, whereas others would just as vehemently regard it as just an isolated helleri.



Obviously, those who have put a lot of effort into the conservation and captive breeding programmes for the Aruba rattler would probably prefer it to be regarded as a separate species rather than just a colour variety...



Bottom line is, it depends on your personal philosophy of what a species is - I know I wouldn't call it one (and I probably wouldn't even call it a subspecies), but I know plenty who would.



Cheers,



Wolfgang



WÜSTER, W., M.G. SALOMÃO, J.A. QUIJADA-MASCAREÑAS, R.S. THORPE & B.B.B.S.P. (2002) Origin and evolution of the South American pitviper fauna: evidence from mitochondrial DNA sequence analysis. In Biology of the Vipers (G.W. Schuett, M. Höggren, M.E. Douglas & H.W. Greene, eds.), pp. 111-128. Eagle Mountain Publishing, Eagle Mountain, Utah.

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