Salazar, Gerardo , Cabrera, Lidia I. , Van Den Berg, Cassio , Smidt, Eric C. , Batista, Joao A. N. , Fraga, Claudio N. , Borba, Eduardo L. , Chase, Mark .
Assessment of generic limits and floral evolution in subtribe Spiranthinae (Orchidaceae, Cranichideae) based on phylogenetic analysis of plastid and nuclear DNA sequences.
Spiranthinae comprise about 400 species of terrestrial orchids largely restricted to the Neotropics, representing one of the major radiations of subfamily Orchidoideae in the New World. Phylogenetic relationships in the subtribe were inferred using parsimony and Bayesian inference of over 5000 bp of combined DNA sequences (nuclear ribosomal ITS region, plastid matK/trnK and trnL/trnF regions) for ca. 200 individuals representing 165 species of Spiranthinae and suitable outgroup taxa. Our data show that morphologically distinctive, monotypic genus Discyphus does not belong to Spiranthinae and recovers Cotylolabium as sister to a strongly supported group that includes four main lineages, namely the Stenorrhynchos, Pelexia, Eurystyles, and Spiranthes clades. Our results reveal instances of generic polyphyly associated with convergence in floral morphology, either as a result of independent adaptation to a same pollinator group (e.g. hummingbirds in Stenorrhynchos s.l.) or of structural simplification due to a reduction in flower size (e.g. Brachystele). The recent proliferation of new genera based on single floral characters or character combinations is for the most part incompatible with strongly supported clades in our molecular trees and results in many genera becoming paraphyletic. This problem is particularly critical in the Pelexia clade,with no less than four "genera" embedded in Cyclopogon and three in Pelexia. Floral features associated with hummingbird pollination, such as a showily colored floral tube and a hard, pointed rostellum are reconstructed as plesiomophic in the subtribe but this syndrome evolved secondarily in bee-pollinated lineages at least two additional times. Our study confirms previous suggestions of evolutionary lability in floral characters directly involved in pollination and provides a firm ground for a revised generic classification of Spiranthinae
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1 - Instituto de Biología, Universidad Nacional Autónoma de México, Departamento de Botánica, Mexico City, Distrito Federal, Mexico
2 - Universidade Estadual de Feira de Santana, Departamento de Ciências Biológicas, Feira de Santana, Bahía, Brazil
3 - Centro Politecnico, Universidade Federal do Parana, Departamento de Botanica, Setor de Ciencias Biologicas, Curitiba, Parana, Brazil
4 - Universidade Federal de Minas Gerais, Departamento de Botânica, Belo Horizonte, Minas Gerais, Brazil
5 - Jardim Botanico do Rio de Janeiro, Rio de Janeiro, Rio de Janeiro, Brazil
6 - Universidade Federal do ABC, Centro de Ciências Naturais e Humanas, Santo André, São Paulo, Brazil
7 - Royal Botanic Gardens, Kew, Jodrell Laboratory, Richmond, Surrey, UK
Presentation Type: Poster:Posters for Sections
Location: Khorassan Ballroom/Chase Park Plaza
Date: Monday, July 11th, 2011
Time: 5:30 PM