The intraspecific taxonomy of the timber rattlesnake has been a subject of considerable controversy, in particular the question of whether the often larger, differently patterned populations from the souther half of the range should be recognised as a separate subspecies, C.h. atricaudatus. Clark et al. (2003) analysed the phylogeography of Crotalus horridus across the eastern United States. Levels of mitochondrial DNA variation in the sampled region (319 b.p.) were small (average pairwise divergence 1.1%), and did not correspond to the conventionally accepted subspecies C. h. horridus and C. h. atricaudatus. Three major mtDNA gene lineages were identified: one is largely restricted to the Atlantic coastal plain from Vermont to Florida, but crosses the Appalachians in western VA, WV and NC; a second is found in most of the range of C. horridus, except the Atlantic coastal plain north of South Carolina; a third is restricted to Missouri. An analysis of molecular variance revealed very low support for the conventional two-subspecies arrangement (which explains only 3.5% of the variance present), whereas an alternative geographic classification dividing the range into southern, northern and western region explained 18.6% of genetic variation.  The observed pattern of higher genetic diversity in southern populations, compared to northern ones, is interpreted as a result of northward expansion following Pleistocene glaciations. The morphological similarities between northwestern and northeastern populations may have evolved independently, in parallel, whereas the "canebrake" phenotype of southern populations may represent the ancestral condition. In view of the absence of reciprocal monophyly between the regional groupings, the authors of this study recommend against the recognition of subspecies, and consider C. horridus a single, monotypic species, while acknowledging the existence of population structure and extensive geographic variation within it. 

• Clark, A.M., P.E. Moler, E.E. Possardt, A.H. Savitzky, W.S. Brown & B.W. Bowen (2003) Phylogeography of the timber rattlesnake (Crotalus horridus) based on mtDNA sequences. Journal of Herpetology 37(1): 145-154.

Atropoides - Jumping vipers

Atropoides nummifer

Castoe et al. (2003) used phylogenetic analysis of two mitochondrial gene sequences to reconstruct the phylogeny of the genus Atropoides. The monophyly of the genus was neither supported nor contradicted by their data. Atropoides nummifer was found to be genetically diverse (up to 10.1% pairwise divergence), and A. olmec was found to rooted among the A. nummifer haplotypes. Moreover, A. olmec haplotypes were recovered not just from the type locality of that species in Veracruz, but also from NE. Oaxaca, Mexico, and Baja Verapaz, Guatemala, suggesting that the species may have a wider distribution than previously anticipated. The various subspecies of A. nummifer probably deserve speciesstatus. However, the authors note that species limit should not be inferred from mitochondrial DNA sequence data alone, and therefore refrain from making any formal changes.

• Castoe, T.A., P.T. Chippindale, J.A. Campbell, L.K. Ammerman & C.L. Parkinson (2003) Molecular systematics of the Middle American jumping pitvipers (genus Atropoides) and phylogeography of the Atropoides nummifer complex. Herpetologica 59: 420-431.
  

Trimersurus tibetanus and T. karanshahi

Tillack et al. studied the available material of green Trimeresurus from Central Nepal and southern Tibet. Morphological characters indicate that the variation of T. karanshahi, described by Orlov & Helfenberger, lies within the range of variation for T. tibetanus Huang, 1982. This is confirmed by low levels of mtDNA sequence divergence between populations from different localities. Consequently, the authors consider T. karanshahi to be conspecific with, and a junior synonym of, T. tibetanus.

• Orlov, N. & N. Helfenberger (1997) New mountain species of Trimeresurus (Serpentes, Viperidae, Crotalinae) of the „green“ pit vipers group from the Himalayas. Russian Journal of Herpetology 4 (2): 195-197.
• Tillack, F. , M. Lorenz, N.L. Orlov, N. Helfenberger, K.B. Shah & W. Eckert (2003) Shah´s Grubenotter Trimeresurus karanshahi Orlov & Helfenberger, 1997 – ein Juniorsynonym von Trimeresurus tibetanus Huang, 1982 (Serpentes: Viperidae: Crotalinae), mit Angaben zur Verbreitung, Biologie und der Vorstellung neuer Farbvarianten aus Zentral-Nepal. [ Shah´s bamboo pitviper, Trimeresurus karanshahi Orlov& Helfenberger, 1997 – a junior synonym of Trimeresurus tibetanus Huang, 1982 (Serpentes: Viperidae: Crotalinae), with notes on the distribution, biology, and the introduction of new colour varieties from Central-Nepal]. Sauria, Berlin, 25 (2): 3-15
  
  

Porthidium porrasi - White-tailed hognosed pitviper

Lamar & Sasa (2003) described a new species of hognosed pitviper, Porthidium porrasi, from the Peninsula de Osa and themainland on the oppsite side of the Golfo Dulce, on the Pacific coast of Costa Rica. The population was previously regarded as a differentiated population of Porthidium nasutum. It differs from P. nasutum in retianing a white tail tip into adulthood, in having 25-27 rather than 23 dorsal scale rows at midbody, and in having a more banded pattern compared to the blotched pattern of P. nasutum. Mitochondrial DNA sequence analysis confiemd the divergecne between the new species and P. nasutum, and its status as the sister species of the latter.

• Lamar, W.W. & M. Sasa (2003) A new species of hognosed pitviper, genus Porthidium, from the southwestern Pacific of Costa Rica (Serpentes: Viperidae). Revista de Biologia Tropical, 51(3-4): 797-804.

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