Revision of the giant geckos of New Caledonia (Reptilia: Diplodactylidae: Rhacodactylus)

Abstract

We employed a molecular phylogenetic approach using the mitochondrial ND2 gene and five associated tRNAs(tryptophan, alanine, asparagine, cysteine, tyrosine) and the nuclear RAG1 gene to investigate relationships within thediplodactylid geckos of New Caledonia and particularly among the giant geckos, Rhacodactylus, a charismatic group oflizards that are extremely popular among herpetoculturalists. The current generic allocation of species within NewCaledonian diplodactylids does not adequately reflect their phylogenetic relationships. Bavayia madjo, a high-elevationendemic is not closely related to other Bavayia or to members of any other genus and is placed in a new genus, Paniegekkogen. nov. Rhacodactylus is not monophyletic. The small-bodied and highly autapomorphic genus Eurydactylodes isembedded within Rhacodactylus as sister to R. chahoua. Rhacodactylus ciliatus and R. sarasinorum are sister taxa but arenot part of the same clade as other giant geckos and the generic name Correlophus Guichenot is resurrected for them.Remaining New Caledonian giant geckos (R. leachianus, R. trachrhynchus, R. auriculatus) receive weak support as amonophyletic group. Although the monophyly of Rhacodactylus (including Eurydactylodes) exclusive of Correlophuscannot be rejected, our results support the recognition of a R. chahoua + Eurydactylodes clade separate fromRhacodactylus sensu stricto. Because of the distinctiveness of Eurydactylodes from R. chahoua (and other NewCaledonian ‘giant geckos’), we retain this name for the four species to which it has been consistently applied and erect anew genus, Mniarogekko gen. nov. to accommodate R. chahoua. There is little genetic differentiation within the narrowlydistributed Corrrelophis sarasinorum, but C. ciliatus from southern New Caledonia are both genetically andmorphologically differentiated from a recently discovered Correlophus from the Îles Belep, north of the Grande Terre,which is here described as C. belepensis sp. nov. Although only subtley different morphologically, the populations ofMniarogekko from the far northwest of the Grande Terre and from the Îles Belep are strongly differentiated geneticallyfrom M. chahoua populations in the central part of the Grande Terre and are described as M. jalu sp. nov. Rhacodactylusauriculatus exhibits some genetic substructure across its nearly island-wide range in New Caledonia, but overalldivergence is minimal. Rhacodactylus leachianus exhibits low levels of divergence across its range and southern insularforms previously assigned to R. l. henkeli are not divergent from southern Grande Terre populations. The few populationsof R. trachyrhynchus sampled are strongly divergent from one another and a specimen from Îlot Môrô near the Île des Pinsis especially distinctive. This specimen and others examined from Îlot Môrô are morphologically assignable to the speciesdescribed by Boulenger in 1878 as Chameleonurus trachycephalus and is recognized here as a full species. New diagnosesare provided for each of the eight genera of endemic New Caledonian diplodactylid geckos now recognized. The resultsof our study necessitate determinations of the conservation status of the new species described or recognized.Mniarogekko jalu sp. nov. is considered Endangered, but is locally abundant. Correlophus belepensis sp. nov. isconsidered Critically Endangered and is restricted to the ultramafic plateaux of Île Art. Although described from the Îledes Pins, we have only been able to confirm the existence of Rhacodactylus trachycephalus on the tiny satellite island ÎlotMôrô and consider it to be Critically Endangered. If indeed restricted to this islet, R. trachycephalus may well have the smallest range and perhaps the smallest population of any gecko in the world.