Phytogeography of Aldama (Asteraceae, Heliantheae) in South America

Abstract A phytogeographical study of Aldama (Asteraceae: Heliantheae) based on extensive field work, literature and herbaria data is presented here. Species were included in ecoregions (Andean and Neotropical) and phytogeographic dominions previously established for Poaceae (Tropical and Subtropical, Warm Temperate and Cold Temperate grasslands). The majority of species belong to the Neotropical Region, and there are also many in Tropical and Subtropical grasslands. Only A. revoluta reaches the Patagonian sub-region of the Andean Region. Western and northern limits of some species are in the Andes Mountains. In contrast, Yungas and Puna regions may be corridors, linking these areas with the east-central area of the genus. In Brazil, the most favorable conditions for diversity and population density of Aldama species occur in areas with megathermal climates (most of the exclusively Brazilian species) or mesothermal climates (seven species), the latter of Köppen types Aw and Cwa, which are related to Cerrado landscapes. The greatest expressivity of Aldama in these open habitats seems to be linked to the thick underground system, which provides water needs during the dry season and fire protection. Four patterns are presented: Exclusive to the South American Transition Zone (10 spp.), Neotropical-transitional (eight spp.), Andean transitional (three spp.) and Neotropical nontransitional (41 spp).