Diversity in Pacific Slender-Toed Geckos, Nactus pelagicus Complex (Reptilia: Squamata), of New Guinea and Adjacent Islands

The diversity within the genus Nactus is slight in comparison to the other Australasian genus of narrow-toed geckos (Cyrtodactylus). The latter now has more than 290 species, with over half of these species newly described in the twenty-first century. In contrast, prior to this study, 12 Nactus species were recognized formally in the recent herpetological literature: three species in the Mascarene Islands, two in the Pacific Islands, three in Australia, and six in New Guinea and associated island groups. Three of these New Guinea species are miniature (snout–vent length ≤ 40 mm) species, and three are in the pelagicus complex; with the exception of the recently described N. kunan, all other New Guinean populations were labeled N. pelagicus even though they were known to be bisexual species and differed from the unisexual N. pelagicus of Oceania. Considering only bisexual New Guinean “pelagicus,” my morphological analyses recognize 24 distinct populations for which I provide new names or resurrected species names from synonymies. Of these 24, two species are extralimital (Morotai and Kei Islands). The sampling of Nactus in Indonesia Papua is very poor, with only one specimen from the base of the Vogelkop, two from south coast drainages, and more than a dozen from islands from the east coast of Cenderawasih Bay; the remainder derive from Papua New Guinea (PNG). The Indonesia Papua populations represent four species, two of which are shared with PNG. Papua New Guinea thus has a total of 20 species, varying from widespread species (e.g., north coast of main Papua to the Sepik-Ramu area) to a single locality in Madang or single islands in the Louisiade Archipelago. Most distributions of the PNG species match at least one other PNG anuran or reptile species. The greatest diversity of PNG species occurs in Madang Province to Huon Peninsula and the Milne Bay mainland with sympatry in both areas. The “pelagicus complex” of species is herein confirmed to be polyphyletic. In spite of its use in this study, its subsequent use should be restricted to the unisexual species and their parental species, of which only one (N. multicarinatus) is known. The preceding represents a subgroup within the larger clade of Australian and New Guinean bisexual species. For the present, I do not recommend a name for this group because a molecular phylogenetic analysis will be required to identify the cladogenesis of the Nactus species.