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Abstract Detail


Systematics/Phytogeography / Taxonomie/ Section

Blaschke, Jeremy D. [1], Sanders, Roger W. [2].

Origin and morphological diversification of Scalesia (Asteraceae), Galápagos Islands.

Scalesia (Asteraceae: Heliantheae) is a woody genus endemic to the Galápagos Islands. The fifteen species offer opportunities to study the degree of adaptation, speciation rates, and patterns of diversification. In preparation for molecular genetic and ecological studies, parsimony analysis was conducted on 64 morphological characters simultaneously in all species of Scalesia, as well as the closely related mainland genera Pappobolus (Andean, 38 spp.) and Simsia (Mexico to Brazil, 18 spp.) and representative species of Viguiera (Mexico to Brazil). Data were extracted from the literature and selected specimens. Consistency indexes were low (0.21) across the 80 ingroup and outgroup taxa. In summary cladograms, Scalesia was usually positioned as sister group to a clade of Viguiera or as a major clade in a trichotomy with Pappobolus + Viguiera spp. and Simsia + Viguiera spp. Synapomorphies of Scalesia included treelet-shrub habit, discoid capitula, three-lobed pales, white corollas, black anthers, and white anther appendages, most of which occurred in various species of Pappobolus and/or Simsia. Under various analysis conditions, basal positions within Scalesia were occupied by either the three tree species (both as clade and grade), the three species with elongate involucral bracts (likewise), or the single species with rays (S. affinis). Bootstrap analysis of 100 replications revealed that Scalesia is supported by 55 percent values, but relationships of all but one pair of species of Pappobolus and Simsia were unresolved. Within Scalesia, one group of four (the lobe-leaved) species and three species pairs were supported above the 76% level. These results support published preliminary molecular analyses that Scalesia originated separately from Pappobolus out of an ancestral complex that existed in Mesoamerica before the Galápagos and Panamanian land bridge both arose. Also, speciation rates may have been slow in Scalesia compared to Pappobolus.


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1 - Bryan College, Biology, Box 7071, 721 Bryan Drive, Dayton, TN, 37321, USA
2 - Bryan College, Biology, Box 7802, 721 Bryan Drive, Dayton, TN, 37321, USA

Keywords:
Scalesia
adaptive radiation
Galápagos Islands.

Presentation Type: Poster:Posters for Sections
Session: P
Location: Ball Room & Party Room/SUB
Date: Monday, July 28th, 2008
Time: 12:30 PM
Number: PSP018
Abstract ID:329


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