New insights into the molecular phylogenetic relationships of lizards in the Neotropical genus Arthrosaura (Reptilia: Gymnophthalmidae) reveal rampant 'cryptic' speciation in the Guiana Shield

The gymnophthalmid lizard genus Arthrosaura currently contains seven species distributed in the Amazonian lowlands and in the Pantepui region. The phylogenetic position and taxonomic status of most species in the genus are surrounded by considerable uncertainty. The type locality of the widespread Ar. reticulata (type species for the genus) is Canelos in Ecuador, but no specimen from Ecuador has ever been included in molecular phylogenies. Here we reassessed the molecular systematics and species' diversity of Arthrosaura based on a multilocus analysis of a six-gene region matrix of an extensive dataset, including several species/populations that had never been sequenced previously, most from close to the type localities. Our results reveal a non-monophyletic Arthrosaura, with Ar. testigensis nested within Yanomamia, and Arthrosaura kockii recovered sister to all other Ecpleopodinae. Rampant 'cryptic' speciation is recovered in the Amazonian lowlands, with at least four undescribed species. The genus is particularly diverse in the Guiana Shield, which harbours nine of the 10 species recovered in our analyses (Ar. kockii excluded). Eight of these species are endemic to the Guiana Shield, four in the western part (west of the Essequibo River), four in the eastern part (east of the Essequibo River).