Geographic structure in two highly diverse lineages of Tillandsia (Bromeliaceae)

Abstract

The Neotropical genus Tillandsia (Bromeliaceae) is an excellent model system for macroevolutionary and biogeographic studies owing to its remarkable species diversity (ca. 650 spp.) and varied morphological and ecological adaptations to epiphytic and saxicolous habitats. Recent phylogenetic studies have greatly improved our knowledge about generic limits and infrageneric classification of Tillandsia. These studies have identified two clades of Tillandsia characterized by a distinct geographic distribution: (i) a North and Central American clade that includes species from subgenus Tillandsia; and (ii) a central South American clade containing species from subgenera Aerobia, Anoplophytum, Diaphoranthema, and Phytarrhiza. Our study aimed to determine the size, composition, and potential geographic structure of these two clades within the context of a global phylogeny of Tillandsioideae. With the addition of 100 newly sequenced species to previous studies to cover the now ca. 30% of the known species diversity of Tillandsia, our analyses found both clades to be strongly supported, and revealed that their species richness is much greater than previously known. Ancestral area estimation suggests that most of the diversification of the first of these clades took place in North and Central America, whereas within the second, most of the migratory events occurred from the Andes to the Brazilian shield.