The rapid radiation of Bomarea (Alstroemeriaceae: Liliales), driven by the rise of the Andes

Abstract

Complex geological events such as mountain uplift affect how, when, and where species originate and go extinct, but measuring those effects is a longstanding challenge. The Andes arose through a series of complex geological processes over the past c. 100 million years, impacting the evolution of regional biota by creating barriers to gene flow, opening up new habitats, and changing local climate patterns. Bomarea are tropical geophytes with ranges extending from central Mexico to central Chile. Of the roughly 120 species of Bomarea, most are found in the Andes, and previous work has suggested that Bomarea diversified rapidly and recently, corresponding with the uplift of the Andes. While many Bomarea species occur over small, isolated ranges, Bomarea edulis occurs significantly beyond the ranges of any other Bomarea species (from central Mexico to northern Argentina) and is thought to have potentially humanmediated dispersal, due to its status as a pre-Columbian food plant. To untangle the potential drivers of diversification and biogeographic history in Bomarea, we used a target-capture approach to sequence nuclear loci of 174 accessions of 124 species, including 16 outgroup species from across the family (Alstroemeriaceae). We included 43 individuals of B. edulis from across its range to assess species monophyly and identify infraspecific phylogeographic patterns. We model biogeographic range evolution in Bomarea and test if Andean orogeny has impacted its diversification. We find that Bomarea originated in the central Andes during the mid-Miocene, then spread north, following the trajectory of major mountain uplift events. Most observed speciation events occurred during the Pleistocene, while global climate cooled and oscillated and the northern Andes achieved their current form. Furthermore, we find that Andean lineages diversified faster than their non-Andean relatives. These results demonstrate a clear macroevolutionary signal of Andean orogeny on this neotropical radiation.