Phylogenetic estimation of the core Bromelioids with an emphasis on the genus Aechmea (Bromeliaceae)

Abstract

We developed a phylogeny of the core Bromelioideae including Aechmea and related genera, with the specific goals of investigating the monophyly of Aechmea and its allied genera, redefining monophyletic lineages for taxonomic revision, and investigating the biogeographic history of the group. Chloroplast, nuclear ribosomal, and low copy nuclear DNA sequences from 150 species within the Bromelioideae were used to develop the phylogeny. Phylogenies constructed with the combined four gene dataset provided sufficient resolution for investigating evolutionary relationships among species. Many genera are nested within Aechmea, or are rendered para- or polyphyletic by inclusion of Aechmea species. Several genera and subgenera of Aechmea with species in disjunct geographic locations are found to be polyphyletic, divided into separate clades that reflect geographic distribution rather than morphological similarity. This suggests that certain morphological characteristics thought to be indicative of common ancestry have instead evolved multiple times in parallel (i.e. ecological conservatism), possibly indicative of local adaptations to an epiphytic habit across the range of the Bromelioideae. These apparently homoplastic morphological characters used to assign species to genera or subgenera may be useful taxonomically when geography is also taken into account.