GIVNISH, THOMAS J.*, KENDRA C. MILLAM, AND KENNETH J. SYTSMA. Department of Botany, University of Wisconsin, Madison, WI 53706. - Phylogenetic relationships and evolutionary patterns in Bromeliaceae based on ndhF sequence variation.
Among commelinoids, bromeliads display low rates of chloroplast
sequence evolution. However, the large, rapidly evolving,
chloroplast-encoded ndhF gene displays useful amounts of sequence
variation for phylogenetic reconstruction. We obtained 17 new ndhF
sequences for major bromeliad groups unsampled in previous surveys to
present a more complete picture of evolution in this important
Neotropical group. Parsimony analysis using members of Poales as
outgroups indicated that Mayaca is sister to Bromeliaceae. The
family itself appears to have arisen in the ancient Guayana Shield,
based on the presence at its base of a grade of genera
(Brocchinia, Lindmania, Connellia) restricted to that region.
Subfamily Tillandsioideae is monophyletic, and also appears to have
arisen in the Guayana Shield, based on its being nested between the
basal grade and another clade (Brewcaria, Navia, “Brocchinia”
serrata) restricted to that region, and based on the present-day
occurrence of the two basal tillandsioid genera (Catopsis,
Glomeropitcairnia) partly or wholly in areas adjacent to the
Guayana Shield. The xeric clade (Abromeitiella, Deuterocohnia,
Dyckia, Encholirium, Hechtia) characterized by tough, succulent
leaves and CAM photosynthesis, is closely related to
Pitcairnia; both groups are sister to a clade composed of
Puya and the subfamily Bromelioideae. The ndhF phylogeny
implies two major migrations from the ancestral Guayana Shield, giving
rise to Tillandsioideae and to Bromelioideae embedded within a grade
of genera formerly assigned to subfamily Pitcairnioideae. The
pitcairnioids are highly paraphyletic and appear to represent five
distinct clades: Brocchinia, Lindmania-Connellia,
Brewcaria-Navia-”Brocchinia serrata”, the xeric clade +
Pitcairnia, and Puya. Epiphytism appears to have arisen
several times in the family, in basalmost Brocchinia, in
tillandsioids, and in bromelioids. Cushion plants at high elevations
in the Andes (Abromeitiella, Deuterocohnia) appear to have
evolved from lowland forms adapted to severe drought.
Key words: Brocchinia, Bromeliaceae, Guayana Shield, Lindmania, Mayaca, Navia