Phylogeny and biogeography of Paepalanthus subg. Platycaulon (Poales: Eriocaulaceae) in the high-Andean páramos of South America : a story of long-distance migration and rapid diversification
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Tropical Andes are located in northern South America and run from northern Chile and Argentina through Bolivia, Peru, Ecuador, Colombia and Venezuela. They are classified as a biodiversity hotspot and harbor more than 20,000 endemic species of plants. Páramos are ecosystems located above 2600 meters of altitude located on the northern portion of the tropical Andes starting in northern Ecuador through Venezuela. Páramos have been available for colonization since the Quaternary, ca. 4 mya, and currently have ca. 3,300 species of plants. The páramo flora is a mixture of tropical and temperate elements and only by studying them we are able to understand the evolutionary history behind the current páramo plant diversity. Erioculaceae is a pantropical family present in the páramos and other highland formations of South America such as campos de altitude in the Brazilian shield and the tepuis in the Guiana shield. The most speciose genus in the family is Paepalanthus, which is divided into six subgenera; P. subg. Platycaulon is the only subgenus with a disjunct distribution in the páramos and the campos rupestres in the Brazilian shield. Previous studies have reconstructed the evolutionary history of Erioculaceae, but their results about P. subg. Platycaulon are not conclusive because they did not include páramo species in their analyses. The main goal of the present study is to evaluate the monophyly of páramo species of Erioculaceae, as well as to investigate their age, origin and possible forces that could be driving their evolution in the páramos. In order to answer these questions, we used plastid and nuclear molecular markers as well as genome sequences to reconstruct the phylogenetic and biogeographical history of P. subg. Platycaulon. Our results show that páramos species of P. subg. Platycaulon are not monophyletic and most of them come from Brazilian ancestors and are 2 my old or less. Incongruence between plastid and nuclear genome data supports the hypothesis of gene flow between páramo species of P. subg. Platycaulon.