Journal Article

Molecular Phylogeny of the Neotropical Genus <i>Christensonella</i> (Orchidaceae, Maxillariinae): Species Delimitation and Insights into Chromosome Evolution

Samantha Koehler, Juliano S. Cabral, W. Mark Whitten, Norris H. Williams, Rodrigo B. Singer, Kurt M. Neubig, Marcelo Guerra, Anete P. Souza and Maria do Carmo E. Amaral

in Annals of Botany

Published on behalf of The Annals of Botany Company

Volume 102, issue 4, pages 491-507
Published in print October 2008 | ISSN: 0305-7364
Published online August 2008 | e-ISSN: 1095-8290 | DOI:
Molecular Phylogeny of the Neotropical Genus Christensonella (Orchidaceae, Maxillariinae): Species Delimitation and Insights into Chromosome Evolution

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  • Ecology and Conservation
  • Evolutionary Biology
  • Plant Sciences and Forestry


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Background and Aims

Species' boundaries applied within Christensonella have varied due to the continuous pattern of variation and mosaic distribution of diagnostic characters. The main goals of this study were to revise the species' delimitation and propose a more stable classification for this genus. In order to achieve these aims phylogenetic relationships were inferred using DNA sequence data and cytological diversity within Christensonella was examined based on chromosome counts and heterochromatin patterns. The results presented describe sets of diagnostic morphological characters that can be used for species' identification.


Phylogenetic studies were based on sequence data of nuclear and plastid regions, analysed using maximum parsimony and maximum likelihood criteria. Cytogenetic observations of mitotic cells were conducted using CMA and DAPI fluorochromes.

Key Results

Six of 21 currently accepted species were recovered. The results also support recognition of the ‘C. pumila’ clade as a single species. Molecular phylogenetic relationships within the ‘C. acicularisC. madida’ and ‘C. ferdinandianaC. neowiedii’ species' complexes were not resolved and require further study. Deeper relationships were incongruent between plastid and nuclear trees, but with no strong bootstrap support for either, except for the position of C. vernicosa. Cytogenetic data indicated chromosome numbers of 2n = 36, 38 and 76, and with substantial variation in the presence and location of CMA/DAPI heterochromatin bands.


The recognition of ten species of Christensonella is proposed according to the molecular and cytogenetic patterns observed. In addition, diagnostic morphological characters are presented for each recognized species. Banding patterns and chromosome counts suggest the occurrence of centric fusion/fission events, especially for C. ferdinandiana. The results suggest that 2n = 36 karyotypes evolved from 2n = 38 through descendent dysploidy. Patterns of heterochromatin distribution and other karyotypic data proved to be a valuable source of information to understand evolutionary patterns within Maxillariinae orchids.

Keywords: Chromosome number; Christensonella; Cymbidieae; cytotaxonomy; fluorochrome staining; Maxillaria; Maxillariinae; molecular phylogenetics; species delimitation

Journal Article.  9822 words.  Illustrated.

Subjects: Ecology and Conservation ; Evolutionary Biology ; Plant Sciences and Forestry

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