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Nagy, Z. T., Glaw, F. & Vences, M. (2010) Systematics of the snake genera Stenophis and Lycodryas from Madagascar and the Comoros. — Zoologica Scripta, 39, 426–435. Arboreal snakes belonging to the pseudoxyrhophiine genus Stenophis inhabit Madagascar but despite their spectacular appearance, surprisingly little is known about their natural history and systematics. Nonetheless, a close phylogenetic affinity of the genera Stenophis and Lycodryas (the latter genus currently includes a single species from the Comoros) has been hypothesized. Based on recent molecular genetic data, however, the monophyly of Stenophis was challenged. This study aimed at a systematic analysis and taxonomic revision of the genera Stenophis and Lycodryas. On the basis of new molecular genetic and morphological data and analyses, we propose to accommodate these snakes in three monophyletic genera: Lycodryas, Phisalixella and Parastenophis, and to consider Stenophis as a junior synonym of Lycodryas. In the new generic arrangement, the genera can also be well distinguished by morphological characters. On the specific level, Phisalixella tulearensis is resurrected and indications of further, undescribed taxa are revealed. [ABSTRACT FROM AUTHOR]

The iguanid subfamily Oplurinae consists of seven species of small to medium-sized, arboreal, sand-dwelling or rock-dwelling lizards endemic to Madagascar and the Comoros, belonging to the genera Oplurus and Chalarodon. We here present the first complete molecular species-level phylogeny for Oplurinae based on DNA sequences (865 bp) of the mitochondrial 16S rRNA gene and the nuclear c-mos gene. Our study is based on 52 specimens sampled from different populations in Madagascar and includes the geographically isolated population from Grande Comore, hitherto considered as subspecies Oplurus cuvieri comorensis or even as a separate species O. comorensis. Our results confirm that, within the genus Oplurus, the largely arboreal O. cuvieri and O. cyclurus form the sister clade to the remaining, more rock-dwelling species. Within the latter lineage, Oplurus quadrimaculatus is placed most basal, O. fierinensis and O. grandidieri are closely related sister species with high support, and O. saxicola is sister to the fierinensis/grandidieri lineage. Within the arboreal Oplurus, the Comoran sample shows no genetic differentiation relative to O. cuvieri populations from the North West and Sambirano regions of Madagascar, indicating that this population should not be considered as a separate species. In the monotypic genus Chalarodon, we discovered deep genetic divergences among populations of C. madagascariensis indicating the presence of a previously unrecognized cryptic species and the need for taxonomic revision. [ABSTRACT FROM AUTHOR]

Previous genetic studies of frogs from Mayotte Island (a French Overseas Department in the Comoros Archipelago) in the Western Indian Ocean have provided evidence for oceanic dispersal in amphibians, which is a rare phenomenon due to the osmotic intolerance of amphibians to saline water. Using an integrative approach including morphological, bioacoustic, and genetic evidence, we here confirm that these frogs correspond to two new species and are the only representatives of the family Mantellidae not endemic to Madagascar. Blommersia transmarina sp. nov. differs from its sister taxon, B. wittei, by several morphological differences including larger body size (snout-vent length up to 34.5 mm) and by slight differences in advertisement calls. Boophis nauticus sp. nov. differs from its closest relatives, B. tephraeomystax and B. doulioti, by slight morphological differences (including larger body size), a reddish (vs. silvery or golden) iris coloration in life, and slightly different advertisement calls. The two new species differ from their closest relatives by a substantial genetic differentiation, with pairwise genetic distances > 5% in the mitochondrial 16S rRNA gene, and based on the limited available data, also by distinct differences in nuclear DNA. They also are both larger than their closest relatives from Madagascar and B. transmarina sp. nov. is the largest Blommersia species, suggesting a moderate form of island gigantism. The Madagascan sister species B. wittei and B. doulioti are among the relatively few amphibian species occurring in the arid western biomes of the island, are adapted to open landscape, and reproduce in stagnant water bodies, which we hypothesize may represent important preadaptations for successful overseas colonization.

Amphibians are thought to be unable to disperse over ocean barriers because they do not tolerate the osmotic stress of salt water. Their distribution patterns have therefore generally been explained by vicariance biogeography. Here, we present compelling evidence for overseas dispersal of frogs in the Indian Ocean region based on the discovery of two endemic species on Mayotte. This island belongs to the Comoro archipelago, which is entirely volcanic and surrounded by sea depths of more than 3500 m. This constitutes the first observation of endemic amphibians on oceanic islands that did not have any past physical contact to other land masses. The two species of frogs had previously been thought to be nonendemic and introduced from Madagascar, but clearly represent new species based on their morphological and genetic differentiation. They belong to the genera Mantidactylus and Boophis in the family Mantellidae that is otherwise restricted to Madagascar, and are distinguished by morphology and mitochondrial and nuclear DNA sequences from mantellid species occurring in Madagascar. This discovery permits us to update and test molecular clocks for frogs distributed in this region. The new calibrations are in agreement with previous rate estimates and indicate two further Cenozoic transmarine dispersal events that had previously been interpreted as vicariance: hyperoliid frogs from Africa to Madagascar (Heterixalus) and from Madagascar to the Seychelles islands (Tachycnemis). Our results provide the strongest evidence so far that overseas dispersal of amphibians exists and is no rare exception, although vicariance certainly retains much of its importance in explaining amphibian biogeography.