North Andean origin and diversification of the largest ithomiine butterfly genus

The Neotropics harbour the most diverse flora and fauna on Earth. The Andes are a major centre of diversification and source of diversity for adjacent areas in plants and vertebrates, but studies on insects remain scarce, even though they constitute the largest fraction of terrestrial biodiversity. Here, we combine molecular and morphological characters to generate a dated phylogeny of the butterfly genus $\textit{Pteronymia}$ (Nymphalidae: Danainae), which we use to infer spatial, elevational and temporal diversification patterns. We first propose six taxonomic changes that raise the generic species total to 53, making $\textit{Pteronymia}$ the most diverse genus of the tribe Ithomiini. Our biogeographic reconstruction shows that $\textit{Pteronymia}$ originated in the Northern Andes, where it diversified extensively. Some lineages colonized lowlands and adjacent montane areas, but diversification in those areas remained scarce. The recent colonization of lowland areas was reflected by an increase in the rate of evolution of species' elevational ranges towards present. By contrast, speciation rate decelerated with time, with no extinction. The geological history of the Andes and adjacent regions have likely contributed to $\textit{Pteronymia}$ diversification by providing compartmentalized habitats and an array of biotic and abiotic conditions, and by limiting dispersal between some areas while promoting interchange across others.ME acknowledges financial support from ANR SPECREP and CNRS (France) and the Leverhulme trust (UK). LDS’s postdoc was funded by an ATIP (CNRS, France) grant awarded to ME. NC was funded by a doctoral grant from the Doctoral School 227 (Sciences de la Nature et de l’Homme: Evolution et Ecologie, France). KW acknowledges funding from NSF (DEB-0639861, DEB-0103746), the National Geographic Society, the Darwin Initiative and the Leverhulme Trust. A.V.L.F. thanks CNPq (fellowships 302585/2011-7 and 303834/2015-3), RedeLep-SISBIOTABrasil/CNPq (563332/2010-7), BR-BoL (MCT/CNPq/FNDCT 50/2010) and FAPESP (BIOTA-FAPESP Programs 2011/50225-3, 2012/50260-6 and 2013/50297-0). KLSB acknowledges support by FAPESP (2012/16266-6). Support for components of this work was provided through a collaborative grant, Dimensions US-Biota-São Paulo, supported by the US National Science Foundation (NSF DEB 1241056), National Aeronautics and Space Administration (NASA), and the Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP Grant 2012/50260-6). Molecular work was performed at the GenePool (University of Edinburgh, UK), UCL (UK) and the Service of Molecular Systematics UMS2700 of the MNHN (France). Work by SK and TS to construct the original Solanaceae phylogeny was funded by the National Science Foundation (DEB-0316614)