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The several dozen species of Asian wolf snakes (genus Lycodon) are distributed widely from central to southeast Asia, from regions east of the Caspian Sea, eastern Iran and India to southern China, the Indo-Australian Archipelago, the Ryukyu Islands of Japan, and the Philippines. The genus includes both widespread species (e.g., L. aulicus, whose range spans nearly the entire range of the genus) and other taxa that are narrowly distributed, even endemic to single small islands. A third of the known diversity occurs in the Philippine archipelago, with most of the described Philippines species endemic to the archipelago. This genus of non-venomous snakes is relatively morphologically homogeneous and characters used for diagnosis are often highly variable, which has made the delineation of species boundaries challenging. The position of Lycodon within the subfamily Colubrinae has also been uncertain, although it has been recognized for some time that there is a close affinity with Dinodon.
Coloration varies greatly within Lycodon, but most species can be grouped into one of four distinct color pattern categories: banded, blotched, solid, or speckled. Variation in color patterns, however, has led to confusion over species boundaries. Siler et al. (2013) investigated Lycodon diversification from a phylogenetic perspective, inferring the phylogenetic position of Lycodon among closely related colubrid snakes, examining the evolution of color patterns within this group, and reconsidering the current taxonomy of the group in the context of their molecular phylogenetic analyses. They concluded that although in a few cases there is evidence of previously unrecognized genetic diversity that may result in the eventual recognition of additional cryptic species, diversity within some parts of the Lycodon tree may actually may be overestimated as a result of taxonomic decisions based on color patterns and untested biogeographic expectations. Their results indicated that banded and blotched color patterns have evolved multiple times across the tree, but solid (and possibly speckled) just once.
Siler et al. (2013) concluded that Dinodon species are nested within the Lycodon tree and noted that Dinodon (the more recently described genus) should therefore be treated as a junior synonym of Lycodon. Based on their own molecular phylogenetic studies, Guo et al. (2013) also suggested that Dinodon should be synonymized with Lycodon. Lei et al. (2014) also found that Dinodon species are nested within Lycodon. Based on molecular phylogenetic and morphological analyses, Lei et al. further concluded that Oligodon multizonatum (an endemic species known from Sichuan and possibly Gansu Provinces in China) actually falls within Lycodon as well.
The phylogenetic results of Siler et al. (2013) provide evidence of deeply divergent lineages within some taxa (L. effraensis, L. subcinctus) that may represent cryptic species. Some of the lineage diversity revealed appears to correspond to taxonomic entities previously identified (currently recognized as subspecies or synonyms) and some does not. On the other hand, as noted above, genetic results suggest that species diversity within several clades may be overestimated, rather than underestimated, by current taxonomic treatments. Between these two extremes lie species with moderate genetic structure observed among populations (L. muelleri, L. aulicus complex).
Regarding inferences about the historical biogeography of Lycodon, Siler et al. (2013) note that with few exceptions, the results observed in their study are consistent with many of the biogeographic expectations for vertebrates in Asia and the Philippines (see Siler et al. 2013 for details and discussion).
(Siler et al. 2013 and references therein)