Showing posts with label geckos. Show all posts
Showing posts with label geckos. Show all posts

Sunday, May 15, 2011

Squamate Diversity - Five New Lizards

The blind snake lizard Dibamus dalaiensis 
Thy et al. 2011. Photo credit Neang Thy
The continuing discovery of new species of terrestrial vertebrates is a reminder that the diversity of life is much greater than was thought even 25 years ago. In the last few week five lizards (3 geckos, 1 skink, and 1 blind snake lizard) have been described from Venezuela, Madagascar, Indonesia, and Cambodia.

The blind snake lizard Dibamus dalaiensis ( family Dibamidae) was described from the Phnom Samkos Wildlife Sanctuary in the Cardamom Mountains of Cambodia by  Neang Thy and colleagues. It is significant because it represents a new family, genus and species record for Cambodia and it raise the number of species in the family Diabamus to 23, eight of these species (34%) have been described in the 21st century.

Marcelo Sturaro and Teresa Avila-Pires described two new species of dwarf day geckos of the genus Gonotodes (family Spaheordactylidae); one from eastern Amazonia, in the states of Pará and Amapá in Brazil (Gonatodes nascimentoi), and another from central Colombia, east of the Andes (Gonatodes riveroi), both are species of the Gonatodes concinnatus complex.The describtion of these geckos raise the number of species in the genus Gonatodes to 26, nine (33%) of which have been described in the 21st century.

Skinks make up the largest family of lizards, with more than 1450 known species. Aurelien Miralles and colleagues have described Madascincus arenicola, a new skink from the sand dunes of northern Madagascar. But, also of interest their molecular analysis found two related species (M. polleni and M. intermedius) genetically distinct, but morphologically indistinguishable. Madascincus now contains 11 species, 2 of which were described in the 21st century.

Djoko Iskandar and colleagues have described Cyrtodactylus batik a new species collected from Mount Tompotika, in the Balantak Mountains of Central Sulawesi, Indonesia. This large Cyrtodactylus (up to 115 mm in body length), forms a lineage with C. wallacei and C. jellesmae that appears to be endemic to Sulawesi. This raises the number of Cyrtodactylus geckos to 139, 59 (42%) of which have been described in the 21st century.

The message here - squamates are much more diverse than previously thought.

Iskandar, D. T., A. Rachmansah and Umilaela. 2011. A new bent-toed gecko of the genus Cyrtodactylus Gray, 1827 (Reptilia, Gekkonidae) from Mount Tompotika, eastern peninsula of Sulawesi, Indonesia. Zootaxa 2838:65-78.

Miralles, A.,  Kohler, J., Glaw, F., and M Vences. 2011. A molecular phylogeny of the “Madascincus polleni species complex”, with description of a new species of scincid lizard from the coastal dune area of northern Madagascar. Zootaxa 2876:1-16.

Thy, N., Holden, J, Eastoe, T., Rathea Seng, Saveng Ith, and Grismer, L.L. 2011. A new species of Dibamus (Squamata: Dibamidae) from Phnom Samkos Wildlife Sanctuary, southwestern Cardamom Mountains, Cambodia. Zootaxa 2828:58-68.

Sturaro, M. J. and T. C. S. Avila-Pires. 2011. Taxonomic revision of the geckos of the Gonatodes concinnatus complex (Squamata: Sphaerodactylidae), with description of two new species. Zootaxa 2869:1-36.

Sunday, December 19, 2010

Sex Determination in Gekkota

The Leopard Gecko, Eublepharis maculatus, is
one of the best studied geckos in terms of its
sex-determination mechanism. JCM
The known number of sex determining mechanisms and variations on them seem to be ever increasing in reptiles as we learn more about them. There are species with male and female heterogamety - sex chromosomes; species with temperature-dependent sex determination, and species with both systems. Within each of these there seems to be many variations. Geckos (Gekkota) are the second most specious lineage of lizards (skinks are the first) with more than 1300 species placed in six different families. The diversity of geckos and their sex determination mechanisms make them excellent candidates for studying the evolution of these mechanisms and current knowledge suggests that geckos have transitioned from one mechanism to another many times during their evolutionary history. Yet, of the 1300 species, relatively few (about 46) have been examined for the mechanisms they use. Tony Gamble of the University of Minnesota has recently summarized the sex determination mechanisms used by geckos in various lineages and discovered that at least 8 or 9 transitions have occurred within the last 150 million years, despite the low number of species that have been examined to date. The Carphodactylidae has not been studies at in this regard, and the Diplodactylidae, Phyllodactylidae, and Sphaerodactylidae are poorly known in terms of how they determination the sex of their offspring. Gamble’s work suggests the ancestral gecko used male heterogamety as the determining mechanism with temperature-dependent sex determination evolving 5 times independently from a genetic sex determination ancestor.