From pampa to puna: Biogeography and diversification of a group of Neotropical obligate grassland birds (Anthus: Motacillidae)

The evolution of Neotropical birds of open landscapes remains largely unstudied. We investigate the diversification and biogeography of a group of Neotropical obligate grassland birds (Anthus: Motacillidae). We use a multilocus phylogeny of 22 taxa of Anthus to test the hypothesis that these birds radiated contemporaneously with the development of grasslands in South America. We employ the R package DDD to analyze the dynamics of Anthus diversification across time in Neotropical grasslands, explicitly testing for shifts in dynamics associated with the Miocene development of grasslands, the putative Pleistocene expansion of arid lowland biomes, and Pleistocene sundering of Andean highland grasslands. A lineage‐through‐time plot revealed increases in the number of lineages, and DDD detected shifts to a higher clade‐level carrying capacity during the late Miocene, indicating an early burst of diversification associated with grassland colonization. However, we could not corroborate the shift using power analysis, probably reflecting the small number of tips in our tree. We found evidence of a divergence at ~1 Mya between northern and southern Amazonian populations of Anthus lutescens, countering Haffer's idea of Pleistocene expansion of open biomes in the Amazon Basin. We used BioGeoBears to investigate ancestral areas and directionality of colonization of Neotropical grasslands. Members of the genus diversified into, out of, and within the Andes, within‐Andean diversification being mostly Pleistocene in origin. Our study highlights the diversification of a group of grassland specialist songbirds in the Neotropics. All Neotropical grasslands contain one or more species of Anthus. Initial diversification occurred in the lowlands, while diversification in the Andes is mostly Pleistocene in origin. Anthus dispersed into, out of, and within the Andes. An uptick in diversification occurred during the late Miocene, a period which co‐occurs with the development of Neotropical grasslands.