Abstract

The Atacama Desert in western South America is considered as one of the driest places on earth, but is nevertheless characterized by surprisingly high species richness and levels of endemism. The plant genus Cristaria (Malvaceae), with ca. 21 species, is one of the most diverse genera of the Atacama Desert, while the much less diverse sister genus Lecanophora (7 species) is found east of the Andes. Here, we use DNA sequence data and divergence time estimates in order to investigate the biogeographical history of the Atacama species of Cristaria. We further investigate a possible influence of Andean uplift and the subsequent onset of hyperaridity in the Atacama Desert on diversification times in Cristaria. We sequenced three plastid markers (ndhF, trnK(matK) & rpl16) for 19 species of Cristaria and two species of Lecanophora from the Atacama Desert and Argentina, respectively. Further, we included sequences of the same plastid regions from GenBank in order to get a comprehensive dataset of Malvoideae. Phylogenetic relationships were inferred using maximum likelihood and Bayesian analyses, and divergence times were estimated with BEAST2. Our results place the monophyletic genera Cristaria and Lecanophora as sister groups in a Glade sister to the rest of Malveae. The split between these two lineages (similar to 20 Ma) correlates with Andean uplift during the early Miocene, indicating a vicariant event. During the late Miocene, two Mediterranean members of Cristaria separated from the major Atacama Glade. The subsequent diversification of the latter one correlates with the onset and subsequent temporal expansion of hyperarid conditions in the Atacama Desert since the late Miocene and during the Quaternary climate oscillations.