Changes in Rhacodactylus

The Rhacodactylus genus as it has been known in herpetoculture has effectively been blown apart! Based on genetic profiling, Rhacodactylus is no longer considered monophyletic, which means that they don’t fit neatly into a tightly packaged descent group. They are still highly related, but some species form more of an extended family instead of being composed entirely of sister taxa.

The latest paper by Aaron Bauer, the leading authority in Rhacodactylus taxonomy, and others has been in the works since at least 2004. After the 2006 New Caledonian Gecko Symposium, rumors have been whispered that big changes were coming; and the paper recently released in Zootaxa 3404: 1–52 (31 Jul. 2012) confirms it. The previously acknowledged species now comprise three genera: Rhacodactylus (3 species remain), Correlophus (2 species recognized), Mniarogekko (2 species recognized). The genus Eurydactylodes is embedded within this former Rhacodactylus group as sister taxa to the Mniarogekko.

It is still uncertain how we will be referring to the group formerly known as Rhacodactylus – the New Caledonian “giant” Geckos – in the future, since including the much smaller Eurydactylodes is a bit paradoxical!

Three of the original Rhacodactylus species remain extant in the genus: R. leachianus, the type species of the genus, R. auriculatus, and both R. trachycephalus and R. trachyrhynchus. R. leachianus is a single species, encompassing some variation in morphology to be expected on insular island populations. The Island and Mainland morphs of leachies are, for genetic typing purposes, the same species. R. auriculatus (Gargoyle Geckos) showed minimal levels of variance except at the northern reaches of their range; however, they still represent variation within a single species. A new book on Gargoyles has been published by Philippe de Vosjoli, Allen Repashy, and Frank Fast – the authors of the popular “Rhac Bible” Rhacodactylus: The Complete Guide to their Selection and Care, which is now out of print.

After the genetic reclassifications, R. trachycephalus is the only endangered Rhac and has a severely limited range, and has “perhaps the smallest population of any gecko in the world.” (Bauer et al., 2012)

Two species formerly classified as Rhacodactylus, R. sarasinorum and R. ciliatus, have now been reclassified as sister species within the genus Correlophus. C. sarasinorum is a single species, despite earlier evidence of two distinct species or a possible subspecies. C. ciliatus as a species displays a wide variety of intraspecies variation. This variation was so great, in fact, that a new species was named for the highly divergent population found on the Northwest Belep Island. C. belepensis is considered Critically Endangered.

Note: It is thought that the current captive population of Crested Geckos is likely restricted to Isle of Pines specimens, which have less overall variation than the mainland (with the exception of Riviere Blue). We will be on the lookout for any further information which may speculate on the presence of C. belepensis in captivity.

The last group of the New Caledonian Giant Geckos to be reclassified is the former R. chahoua. These are now the “angels and demons” of the genus Mniarogekko, the new taxa for chewies. M. chahoua & M. jalu (chahoua means devil while jalu means spirit). M. chahoua is identified as the Central & Southern mainland population, with M. jalu occupying the far Northern range of Grand Terre. It is unclear whether M. jalu has a narrowly restricted range or if it is indeed present in the rest of the mainland; the populations found thus far have been north of Koumac, with populations found in the Belep archipelago alongside populations of C. belepensis.

Neither species of Mniarogecko was found in Isle of Pines that Bauer et al. could document. It is only speculation at this point that chewies reportedly collected from this area now in the pet trade are M. chahoua. The paper notes that as a whole, the geckos differ very little morphologically but exibit a great genetic diversity between the two species. This makes distinguishing M. chahouha from M. jalu in the captive population a challenge, and the paper speculates that there may be several crosses between the two as well as some pure specimens.

To sum up:

  • The New Caledonian giant geckos are a non-monophyletic group
  • The group now includes Eurydactylodes
  • Rhacodactylus includes Leachies, Gargoyles and Trachys
  • Correlophus includes Sarasinorum and Crested Geckos, which has a new subspecies C. belepensis
  • Mniarogekko includes two recognized species of Chahoua, M. chahoua and M. jalu, which is restricted to the northern mainland