|Cyrtodactylus tanim |
Nielsen & Oliver, 2017
Exposed limestone karst landscapes, especially in the tropics, are often home to distinctive and specialized biotas. Among vertebrates, a particularly large number of karst-associated lizard taxa have been described, but for the vast majority, evidence of specific adaptions to karst is lacking. A number of studies, however, have provided evidence of consistent morphological trends in lizards that use complex, three-dimensional, saxicoline habitats such as those that typify karst areas. Here we combine morphological and genetic data to test whether a newly discovered gecko from an extremely rugged karst area in New Guinea shows morphological trends matching those observed in other lizards associated with complex rock habitats such as karst and caves. Consistent with predictions, the new species' head is flatter and narrower than similar-sized relatives, and it has proportionally larger eyes and longer limbs. These trends indicate this taxon represents the second documented instance of karst specialization in a New Guinean vertebrate, and suggest morphological traits to test for evidence of specialized ecological associations in the many karst-associated Cyrtodactylus taxa from Southeast Asia.
KEYWORDS: Cyrtodactylus, ecological diversity, gecko, morphometric analysis, specialization
|Figure 7. Cyrtodactylus tanim n. sp. in life. Paratypes SJR14637 (a,b) and NMV75961 (c) displaying juvenile coloration.|
Photographs: Paul M. Oliver.
Cyrtodactylus tanim n. sp.
Diagnosis: Cyrtodactylus tanim n. sp. can be distinguished from all other Melanesian and (Wallacean) Cyrtodactylus by the following unique combination of characters: moderate size (SVL to 96.7 mm) and slender, with a relatively narrow head (HW/SVL 0.17–0.19), mid-dorsal tubercles in 14–16 longitudinal rows at midpoint of body, ventrolateral fold without enlarged tubercles, subcaudal scales not transversely widened, pores in a tripartite series, precloacal pores obvious and of moderate number (15–17), femoral pores minute and numerous (31–30 per limb, 66–76 total), and dorsal colour pattern on torso consisting of six to nine semi-distinctly defined, alternating dark-brown bands or blotches, on a medium-brown background.
Distribution and natural history: Currently known from three sites spanning an elevation from approximately 540 to 1075 m.a.s.l. in near-impenetrable limestone country just east of Kaiangabip Village, Western Province, Papua New Guinea. Similar limestone country is widespread, but difficult to access, along the southern edge of the Central Cordillera, and this species is likely to have a wider range than is currently known.
A similar, moderately sized Cyrtodactylus with many dark-brown dorsal bands was seen—but not collected—in limestone areas in the north of Gulf Province. If this is also Cyrtodactylus tanim n. sp., then it will have a range spanning over 300 km.
Cyrtodactylus tanim n. sp. was collected in hill forest and lower montane forest where it was quite common, especially at higher elevations. Along a ridge of lower montane forest at approximately 1100 m.a.s.l. (figure 8), up to 10 specimens could reliably be seen over several hours of spotlighting on a single night. They were most commonly seen perched at relatively low heights (less than 3 m above substrate) on limestone faces, or on nearby small trees, roots, or lianas. Two eggs are visible in paratypes (NMV75958 and NMV75959) at varying stages of development.
Above 1000 m.a.s.l. Cyrtodactylus tanim n. sp. was the only gecko present, but at the two lower elevation sites (less than 900 m.a.s.l.) it occurred sympatrically with C. capreoloides and C. serratus. No habitat segregation with the former was obvious. Cyrtodactylus serratus appeared to be much rarer (six specimens in three weeks) and was observed at greater heights in the forest strata (e.g. on lianas or in larger forest trees more than 3 m above the ground), suggesting this much larger species is more arboreal than Cyrtodactylus tanim n. sp.
|Figure 8. Habitat of Cyrtodactylus tanim n. sp.: lower montane forest on karst basement in Western Province, Papua New Guinea. Photograph: Paul M. Oliver.|
Etymology: ‘Tanim’, ‘Tanem’ or ‘Tanemkan’ is the ‘tokples’ name that Faiwol speakers from western Papua New Guinea gave specifically for Cyrtodactylus geckos, both on this survey, and earlier surveys undertaken by Fred Parker around Wangbin and Migalsimbip Villages in 1969 (personal communication). Incidentally, several local people including experienced hunters, showed distaste for Cyrtodactylus geckos, and were reluctant to touch, hold, or in the case of large specimens even look at them.
Stuart V. Nielsen and Paul M. Oliver. 2017. Morphological and Genetic Evidence for A New Karst Specialist Lizard from New Guinea (Cyrtodactylus: Gekkonidae). Royal Society Open Science. DOI: 10.1098/rsos.170781