Abstract

The Amazon rainforest is the world’s most extensive tropical rainforest, holding a considerable ecological and taxonomic diversity. Speciation in this region arises from multiple factors, such as topography, climate fluctuations, oceanic transgression, vegetation and the delimitation of zones circumscribed by sub-basins within the greater Amazon basin. Different scenarios have been proposed to better understand the diversification of Amazonian taxa, whether by Pleistocene refugia or by areas of endemism.                The genus Scaria is distributed mostly in Amazonia, with a single species that ranges from the Tumbes-Chocó-Magdalena ecoregion well into Central America all the way to southern Nicaragua. Eight species are currently recognized, with three additional described here as new: Scaria rafaeli sp. nov., S. jonasi sp. nov. and S. granti sp. nov., and the status of S. laeta stat. resurr. is revalidated. Two new combinations are established: S. verutum comb. nov. (formerly placed in Rehnidium Grant, 1956) and Batrachidea brevis comb. nov. (formerly placed in Scaria). New synonym is proposed: Batrachidea brevis (Hancock, 1909) = Batrachidea inermis Hebard, 1923 syn. nov. Lectotypes and paralectotypes were selected for S. laeta, S. maculata and S. lineata, as well as the neotypes for S. hamata and S. boliviana. An updated key to species of Scaria is also provided.                A cladistic analysis for 15 species was performed (12 in the inner group and 3 in the outer group) with 40 morphological characters, confirming the monophyly of Scaria. A biogeographical analysis of dispersion-vicariance indicates that the origin of the genus was probably in the Inambari endemism center as the only reconstruction of the resulting ancestral distribution, five dispersions and three vicariance events being postulated. These suggest that both types of events are equally important in the current configuration of the distribution in Scaria. Vicariance events arise mostly by isolation of the species because of the uplift of the Andes and the dispersion events comprise four waves originating from the ancestral range into central and east Amazonia.