Format: ORAL

Anri Chomentowska1, Sophie Dauerman1, Patrick Sweeney2, Iris Peralta3,4, C. Matt Guilliams5, Monica Arakaki6, Joseph Holtum7, MatthewOgburn8, Lillian Hancock9, Erika Edwards1,2

1 Department of Ecology and Evolutionary Biology, Yale University, Connecticut, USA 2 Peabody Museum, Yale University, Connecticut, USA 3 Facultad de Agronomía, Universidad Nacional del Cuyo, Mendoza, Argentina 4 Instituto Argentino de Investigaciones de las Zonas Áridas, Mendoza, Argentina 5 Santa Barbara Botanic Garden, California, USA 6 Museo de Historia Natural, Universidad Nacional Mayor de San Marcos, Lima, Perú 7 College of Science and Engineering, James Cook University, Queensland, Australia 8 Department of Biology, Southern Utah University, Utah, USA 9 Department of Ecology and Evolutionary Biology, Brown University, Rhode Island, USA

The plant family Montiaceae (Caryophyllales) has an affinity for desert or alpine habitats and exhibits significant evolutionary lability in life history and climate niche. Lability in life history traits has been shown to cluster especially in one South and North American sublineage, the Cistantheae; this clade is distributed in desert and mountain regions from the Andes to the Cascade mountains, but is absent from equatorial regions (amphitropic distribution). Exploring evolutionary patterns in this lineage has been stymied thus far by unresolved phylogenies, exacerbated by decades of taxonomic confusion due to the presence of intraspecific variation in morphology. We aimed to clarify phylogenetic relationships within Cistantheae and delimiting species using various next-generation sequencing techniques, with the ultimate goal of understanding its biogeographical history and biome transitions. We sequenced 460 plant specimens involving 103 putative species (including outgroup taxa) collected largely from Chile, Argentina, Peru, and USA; the sequencing reads were assembled using a whole-genome reference of the species Cistanthe longiscapa. The consequent phylogeny supported genus-level relationships in the Cistantheae, and clarified species relationships in its subsections. Phylogenomic and population genomic approaches showed signatures of gene flow between select populations in smaller geographical ranges; we also inferred multiple long-distance dispersals between continents, with South America acting as the source pool for movements into North America. These analyses support several phylogenetic hypotheses from previous studies and reveal instances where species have been over-split and need taxonomic revision. The phylogeny also raises interesting implications about life history strategies and climate niche evolution, and their role in desert and mountain radiations. Finally, Cistantheae includes multiple rare and highly distinctive species that are vulnerable to extinction––highlighting the necessity for the conservation of their montane habitats and the importance of describing the clade’s biodiversity.