Repeated divergence of amphibians and reptiles across an elevational gradient in northern Madagascar.

How environmental factors shape patterns of biotic diversity in tropical ecosystems is an active field of research, but studies examining the possibility of ecological speciation in terrestrial tropical ecosystems are scarce. We use the isolated rainforest herpetofauna on the Montagne d'Ambre (Amber Mountain) massif in northern Madagascar as a model to explore elevational divergence at the level of populations and communities. Based on intensive sampling and DNA barcoding of amphibians and reptiles along a transect ranging from ca. 470-1470 m above sea level (a.s.l.), we assessed a main peak in species richness at an elevation of ca. 1000 m a.s.l. with 41 species. The proportion of local endemics was highest (about 1/3) at elevations >1100 m a.s.l. Two species of chameleons (Brookesia tuberculata, Calumma linotum) and two species of frogs (Mantidactylus bellyi, M. ambony) studied in depth by newly developed microsatellite markers showed genetic divergence up the slope of the mountain, some quite strong, others very weak, but in each case with genetic breaks between 1100 and 1270 m a.s.l. Genetic clusters were found in transect sections significantly differing in bioclimate and herpetological community composition. A decrease in body size was detected in several species with increasing elevation. The studied rainforest amphibians and reptiles show concordant population genetic differentiation across elevation along with morphological and niche differentiation. Whether this parapatric or microallopatric differentiation will suffice for the completion of speciation is, however, unclear, and available phylogeographic evidence rather suggests that a complex interplay between ecological and allopatric divergence processes is involved in generating the extraordinary species diversity of Madagascar's biota. Our study reveals concordant patterns of diversification among main elevational bands, but suggests that these adaptational processes are only part of the complex of processes leading to species formation, among which geographical isolation is probably also important.

Range Extension and Behavioural Observations of the Recently Described Sheth's Dwarf Lemur (Cheirogaleus shethi).

Sheth's dwarf lemur, Cheirogaleus shethi, is a small, recently discovered nocturnal primate endemic to northern Madagascar. Unlike many other nocturnal lemurs, C. shethi lives sympatrically with morphologically similar species of its cryptic genus, making it difficult for biologists to determine its population density and distribution. Here, we present new data and observations of this species. During a series of rapid biodiversity assessments in the SAVA region of north-eastern Madagascar, we observed C. shethi in 10 different sites, 9 of which were not previously known to harbour C. shethi populations. More significantly, 2 of these sites, in Analamanara, were situated approximately 20 km south of the previously known southern extremity of this species' distribution. This represents a large increase in the previously limited geographic range of this species. Moreover, our relatively high encounter rates at these sites suggest that C. shethi population densities may be high. We also observed C. shethi in human-altered (e.g., vanilla plantations) and non-forest, savannah environments, suggesting that this species can tolerate disturbed habitats. Our findings therefore provide important additional information on the distribution of C. shethi populations and highlight the necessity of further study for the conservation of this species.