Phylogenetic and biogeographic relationships of frailejones (Espeletiinae, Compositae): An ongoing radiation in the tropical Andes

Abstract

The páramos and high Andean forests of the tropical Andes are largely dominated by frailejones (subtribe Espeletiinae Cuatrec., Asteraceae). These plants are ecologically and culturally essential for both ecosystems and local inhabitants. However, taxonomic knowledge of the group is incomplete and fragmentary, and there is no agreement regarding the classification or even the number of species within the subtribe. The most current and complete annotated taxonomic revision of the nomenclature is presented here. Various species or infraspecific taxa are proposed as hybrids, and new records for Colombia are reported. Previous attempts to reconstruct the evolutionary history of this group failed to resolve relationships among genera and species. This study used molecular sequence data from the ITS, ETS and rpl16 regions, and fragment data from 28 primer combinations of AFLPs. Phylogenies reconstructed suggest that various clades are monophyletic, but the phylogenetic signal may be misled by hybridization and incomplete lineage sorting. Sympatric species tend to be more related to each other than to distant species; thus, there is a strong geographic structure illustrated by hotspots of diversity at a regional scale, and by páramo clusters at a local scale. Like the rapidly shrinking páramos, frailejones are highly threatened by climate change, mining, agriculture and livestock. Potential changes in species' geographic distributions under different scenarios of climate change were estimated. In total, future distributions for 133 species were modeled using 23 global climate models under three emissions scenarios for the years 1990 to 2080. Future distributions of frailejones differ considerably between scenarios and global climate models. However, main trends were identified, and a model of explanatory variables is proposed. Most of the species are predicted to experience a reduction in suitable area, with fragmentation and simplification (or extinction) of their populations over time. Species at the extremes of the elevation gradient will suffer the most drastic effects, either increasing or decreasing their suitable areas, with the first extinctions predicted to occur as early as 2020. Overall, an extinction rate of 31-57% is estimated for frailejones species by 2080. Two hotspots with high predicted frequency of extinctions are also identified.