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DOI

10.5642/aliso.20072301.04

First Page

3

Last Page

26

Abstract

Cladistic analysis of ndhF sequences identifies eight major bromeliad clades arranged in ladderlike fashion. The traditional subfamilies Tillandsioideae and Bromelioideae are monophyletic, but Pitcairnioideae are paraphyletic, requiring the description of four new subfamilies, recircumscription of Pitcairnioideae and Navioideae, the sinking of Ayensua, and description of the new genus Sequencia. Brocchinioideae are basalmost, followed by Lindmanioideae, both restricted to the Guayana Shield. Next is an unresolved trichotomy involving Hechtioideae from Central America, Tillandsioideae, and the remaining bromeliads in subfamilies Navioideae, Pitcairnioideae, Puyoideae, and Bromelioideae. Bromeliads arose as C3 terrestrial plants on moist infertile sites in the Guayana Shield roughly 70 Mya, spread centripetally in the New World, and reached tropical West Africa (Pitcairnia feliciana) via long-distance dispersal about 10 Mya. Modern lineages began to diverge from each other 19 Mya and invaded drier areas in Central and South America beginning 15 Mya, coincident with a major adaptive radiation involving the repeated evolution of epiphytism, CAM photosynthesis, impounding leaves, several features of leaf/trichome anatomy, and accelerated diversification at the generic level. This ‘‘bromeliad revolution’’ occurred after the uplift of the northern Andes and shift of the Amazon to its present course. Epiphytism may have accelerated speciation by increasing ability to colonize along the length of the Andes, while favoring the occupation of a cloud-forest landscape frequently dissected by drier valleys. Avian pollination (mainly by hummingbirds) evolved at least twice ca. 13 Mya; entomophily was ancestral. Hechtia, Abromeitiella–Deuterocohnia–Dyckia–Encholirium, and Puya exhibit a remarkable pattern of concerted convergence in six anatomical and physiological leaf traits adapted to drought.