Cladistic Relationships of Aechmea (Bromeliaceae, Bromelioideae) and Allied Genera

Aechmea (ca. 220 species) is the largest and most diverse genus in Bromelioideae (Bromeliaceae), and several dissimilar generic concepts and infrageneric classifications have been proposed, frequently involving other closely related Bromelioideae. A morphology-based phylogenetic analysis using parsimony was conducted with 86 taxa, including 52 Aechmea (7 of the 8 recognized subgenera represented) and 34 exemplars from 9 closely related genera as the ingroup. Two species of Cryptanthus were included as the outgroup. The main objectives were to assess the validity of the major infrageneric classification systems proposed for Aechmea and to elucidate the phylogenetic position of Aechmea and putatively related genera in subfamily Bromelioideae. The topology of the consensus tree suggests that Acanthostachys, Billbergia, Portea, and non-Brazilian Ronnbergia may be monophyletic. Hohenbergia, Streptocalyx, and Quesnelia are paraphyletic or polyphyletic, as are most subgenera of Aechmea, except for subgenera Chevaliera and Macrochordion, which appear monophyletic. Characters traditionally emphasized in classifications of Bromelioideae displayed high levels of homoplasy, and this may be a reason for the artificiality of the taxonomic systems proposed for these taxa. Due to weak internal support, we refrain from recognizing any new taxonomic rearrangements. These results do provide new insights into the relationships within a number of Bromelioideae genera and suggest directions for future studies.