ibclogo XVI International Botanical Congess


Abstract Number: 4280
Session = 3.2.7


BIOGEOGRAPHY AND EVOLUTION OF THE ENDEMIC CACTACEAE OF THE GALAPAGOS ISLANDS


Steven L. Dickie and Robert S. Wallace, Iowa State University


The cactus flora of the Galapagos Islands includes 2 monotypic species from Subfamily Cactioideae (Brachycereus nesioticus, with low clump-forming habit, and the arborescent Jasminocereus thouarsii) and 6 species from Opuntia (some with tree-like growth). Studies to examine evolutionary divergence and systematic placement of these taxa have been initiated using DNA variation. The putative tribal affinities for both Brachycereus and Jasminocereus to mainland taxa in tribes Browningieae, Hylocereeae or Trichocereeae are addressed. For the Opuntia species, the inferred relationships within and among the Galapagos taxa are compared to potentially-related mainland species in addition to addressing aspects of phylogenetic radiation and morphological divergence in the island taxa. Preliminary data support a monophyletic clade for the Galapagos Opuntias, suggesting a single colonization event. Implications of these relationships in interpreting patterns of speciation and geographic dispersal in the endemic island cacti will be presented.


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