Sunday, February 7, 2016

[Herpetology • 2012] Phylogeny and Systematics of Melanesia’s Most Diverse Gecko Lineage (Cyrtodactylus, Gekkonidae), with Description of Cyrtodactylus arcanus & C. medioclivus from New Guinea Highlands (Central Cordillera)

Cyrtodactylus medioclivus
Oliver, Richards & Sistrom, 2012.

The systematics and biogeographical history of the diverse fauna of New Guinea and surrounding islands (Melanesia) remain poorly known. We present a phylogeny for 16 of the 21 recognised Melanesian bent-toed geckos in the genus Cyrtodactylus based on mitochondrial sequence data. These analyses reveal two divergent lineages of Cyrtodactylus within Melanesia. One includes a single recognised species with clear affinities to sampled taxa from Asia. The other comprises a relatively diverse radiation (likely 30+ species), not closely related to sampled extralimital taxa and centred on the Melanesian region (including Australia). Many taxa within this second lineage are endemic to islands surrounding New Guinea, and dispersal and speciation on peripheral islands appears to have played an important role in the accumulation of species diversity within this clade. In contrast, little diversity is centred upon montane areas, although we do identify at least one lineage closely associated with hill and lower montane forest that probably dates to at least the late Miocene. Our phylogenetic analyses also reveal numerous divergent lineages that require taxonomic attention, including at least two widespread taxa that are likely to be composite, additional specimens of Cyrtodactylus capreoloides (until recently known only from the holotype) and several divergent and completely novel lineages, two of which we introduce herein: Cyrtodactylus arcanus sp. n. and Cyrtodactylus medioclivus sp. n.

Figure 2. Photographs in life of (a) Cyrtodactylus capreoloides SAMA R66092, (b) Cyrtodactylus arcanus sp. n. AMS R124559 (holotype) and (c) Cyrtodactylus medioclivus sp. n. SAMAR66091 (holotype).
  Photographs by S. Richards and T. Reardon.  DOI: j.1463-6409.2012.00545.x 

Genus Cyrtodactylus Gray, 1827

Cyrtodactylus arcanus sp. n. 

Etymology.  Latin ‘arcanus’, secret or mysterious, in reference to the paucity of information about this species, specifically the imprecise type locality, and absence of both habitat data and male specimens.

Distribution and natural history.  Currently known only from forests around Bundi on the northern edge of Central Cordillera in Morobe Province (Figure 4). The types were brought into Bundi Village from a village apparently known as ‘Dagbaru’. Searches of several place name databases for Papua New Guinea failed to identify a location in this area with a name matching this. Nothing is known about its ecology or biology.

Cyrtodactylus medioclivus sp. n. 
Cyrtodactylus sp. Richards & Dahl 2011

Eytmology.  Latin ‘medio’ (middle, half) and ‘clivus’ (slopes), in reference to known localities at moderate altitudes at the approximate mid-point of New Guinea, and alluding to this species’ relationship with Cyrtodactylus boreoclivus from the North Papuan Ranges (Oliver et al. 2011).

Distribution and natural history.  Known only from two localities in mossy lower montane forest in Southern Highlands Province (Figure 4). The holotype was collected in very heavy rain on a mossy branch two metres above the ground. Over ten nights of sampling, no other geckos were seen or collected. The paratype was brought in by local collectors and has no associated habitat information other than the details given above.

The level of genetic divergence between the two types of C. medioclivus (4.2%) suggests that they come from genetically divergent populations. While only 100 km apart, it is not surprising that the combination of rugged topography, an apparently narrow altitudinal distribution and historical changes in climate might have generated significant geographic structure within this species. The phylogeography of montane lineages in New Guinea remains almost completely unknown, and more detailed study of this and other taxa with similar distributions is required.

 Paul Oliver, Stephen J Richards and Mark Sistrom. 2012. Phylogeny and Systematics of Melanesia’s Most Diverse Gecko Lineage (Cyrtodactylus, Gekkonidae, Squamata). ZOOLOGICA SCRIPTA. 41(5); 437–454.  DOI: j.1463-6409.2012.00545.x