Molecular phylogenetics of Maxillaria and related genera (Orchidaceae: Cymbidieae) based on combined molecular data sets

Abstract

The orchid genus Maxillaria is one of the largest and most common of neotropical orchid genera, but its current generic boundaries and relationships have long been regarded as artificial. Phylogenetic relationships within subtribe Maxillariinae sensu Dressler (1993) with emphasis on Maxillaria s.l. were inferred using parsimony analyses of individual and combined DNA sequence data. We analyzed a combined matrix of nrITS DNA, the plastid matK gene and flanking trnK intron, and the plastid atpB-rbcL intergenic spacer for 619 individuals representing ca. 354 species. The plastid rpoC1 gene (ca. 2600 bp) was sequenced for 84 selected species and combined in a more limited analysis with the other data sets to provide greater resolution. In a well-resolved, supported consensus, most clades were present in more than one individual analysis. All the currently recognized minor genera of "core" Maxillariinae (Anthosiphon, Chrysocycnis, Cryptocentrum, Cyrtidiorchis, Mormolyca, Pityphyllum, and Trigonidium) are embedded within a polyphyletic Maxillaria s.l. Our results support the recognition of a more restricted Maxillaria, of some previously published segregate genera (Brasiliorchis, Camaridium, Christensonella, Heterotaxis, Ornithidium, Sauvetrea), and of several novel clades at the generic level. These revised monophyletic generic concepts should minimize further nomenclatural changes, encourage monographic studies, and facilitate more focused analyses of character evolution within Maxillariinae.

The genome sequence of the orchid Phalaenopsis equestris

“…As the common ancestor of the crown group of orchids is supposed to have lived during the Late Cretaceous period sometime between 76 and 84 million years ago 13 , this finding would suggest that the orchid-specific WGD event occurred in association with the origin of this clade, and polyploidy is indeed proposed as a frequent mechanism of speciation in angiosperms 31,32 . In contrast, many members of the Orchidaceae family underwent drastic rate shifts (transition and transversion) during their evolutionary history due to periods of accelerated molecular evolution caused by their short life cycles and altered life history strategies [33][34][35] . These rate shifts complicate absolute dating 27 , especially considering the long distant relationship from orchid to the other monocot species for which the complete genome sequence is currently available, such that the current WGD age estimate could be an overestimate, with the actual age most likely closer to the lower confidence interval boundary.…”

Taxonomy of the Subtribe Maxillariinae (Orchidaceae, Vandoideae) revised

“…ex R.Br. Unfortunately, both genera treated in the way proposed by Whitten et al (2007) are questionable. Camaridium and Ornithidium include different species from the morphological point of view; however, the molecular data grouped them into two well-supported clades.…”

“…Independently from Whitten et al (2007), we examined a more or less similar spectrum of species obtaining similar molecular databased trees. However, our conclusions concerning generic circumscriptions of what formerly was called Maxillaria sensu lato and following nomenclatural consequences are different.…”

Morphometric analysis of the Brasiliorchis picta complex (Orchidaceae)

“…One of these subgroups, the so called Maxillaria picta complex, in which most species have bifoliate pseudobulbs and occur exclusively in Brazil, is known by its extensive morphological variation, which entails several problems to delimit its species. Anatomical (Holtzmeier et al 1998) and molecular (Dathe & Dietrich 2006, Whitten et al 2007) data show a monophyletic group which includes the species of this complex, and occurs only in Brazilian atlantic and seasonal deciduous forests. This group was recently transferred for the genus Brasiliorchis , and here we adopt this criterion.…”

“…is considered (Holtzmeier et al 1998). Dathe & Dietrich (2006) and Whitten et al (2007), whose sampling included different species of Maxillaria and such closely related genera as Camaridium Lindl., Ornithidium Saliob. ex R.…”