Molecular phylogenetics of Vandeae (Orchidaceae) and the evolution of leaflessness

Abstract

Members of tribe Vandeae (Orchidaceae) form a large, pantropical clade of horticulturally important epiphytes. Monopodial leafless members of Vandeae have undergone extreme reduction in habit and represent a novel adaptation to the canopy environment in tropical Africa, Asia, and America. To study the evolution of monopodial leaflessness, molecular and structural evidence was used to generate phylogenetic hypotheses for Vandeae. Molecular analyses used sequence data from ITS nrDNA, trnL-F plastid DNA, and matK plastid DNA. Maximum parsimony analyses of these three DNA regions each supported two subtribes within monopodial Vandeae: Aeridinae and a combined Angraecinae + Aerangidinae. Adding structural characters to sequence data resulted in trees with more homoplasy, but gave fewer trees each with more well-supported clades than either data set alone. Two techniques for examining character evolution were compared: (1) mapping vegetative characters onto a molecular topology and (2) tracing vegetative characters onto a combined structural and molecular topology. In both cases, structural synapomorphies supporting monopodial Vandeae were nearly identical. A change in leaf morphology (usually reduced to a nonphotosynthetic scale), monopodial growth habit, and aeration complexes for gas exchange in photosynthetic roots seem to be the most important characters in making the evolutionary transition to leaflessness.

Phylogenetic utility of ycf1 in orchids: a plastid gene more variable than matK

“…The ITS region is more variable and yielded more PICs than either mat K or ycf 1 in the species--level analysis of Elleanthus and Sobralia . However, in the analysis of tribe Vandeae, ycf 1 yielded more PICs and a longer tree than ITS and mat K. Minor incongruence exists among data sets in our genus--level (Carlsward et al 2006 ) and species--level (Sobralia and Elleanthus ) analyses, but lack strong bootstrap support. Incongruence is common when comparing multiple datasets and can be caused by many different biological, experimental, or analytical reasons (Johnson and Soltis 1998 ;Buckley et al 2001 ).…”

Taeniophyllum norfolkianum: a second genus of Vandeae (Orchidaceae) indigenous to New Zealand

“…However, T. norfolkianum may be the only epiphytic orchid to have migrated to NZ in historic times: all others have been terrestrials. ECOLOGY: Leaflessness has evolved six or seven times, and in different ways, within the Vandeae, with three or four independent origins in Asia in ancestors of Taeniophyllum, Chiloschista and Phalaenopsis (Carlsward et al 2006). The presence of cortical stomatal complexes in the roots, a synapomorphy of Vandeae, may be an important structural precursor to leaflessness, by enabling roots to engage in controlled gas exchange (Carlsward et al 2006).…”

“…ECOLOGY: Leaflessness has evolved six or seven times, and in different ways, within the Vandeae, with three or four independent origins in Asia in ancestors of Taeniophyllum, Chiloschista and Phalaenopsis (Carlsward et al 2006). The presence of cortical stomatal complexes in the roots, a synapomorphy of Vandeae, may be an important structural precursor to leaflessness, by enabling roots to engage in controlled gas exchange (Carlsward et al 2006). The limited carbon investment in vegetative organs associated with leaflessness may have facilitated radiation into marginal microsites, such as those subject to severe water stress, or physically incapable of supporting modest epiphyte loadings.…”

“…Taeniophyllum norfolkianum: a second genus of Vandeae (Orchidaceae) indigenous to New Zealand Introduction Taeniophyllum is the largest exclusively leafless genus within the Vandeae (Carlsward et al 2006), whose species are primarily branch and twig specialist species. Their roots contain chlorophyll and take over the organic nutrition of the plant.…”

DIVERSITY OF Vanda tricolor Lindl. (ORCHIDACEAE) FLOWER-VISITING INSECTS IN THE TURGO HILL OF MOUNT MERAPI NATIONAL PARK, YOGYAKARTA, INDONESIA

“…Susantyo (2011) reported plant biodiversity from this place and Vanda tricolor was recorded in Mount Merapi National Park as a native orchid species. V. tricolor belongs to Orchidaceae, tribe Vandeae (Carlsward et al, 2006), which has a pleasant fragrant and a red-purple-brown attractive colour (Cullen, 1992). The distributions of V.tricolor in Indonesia were reported in West Java, Central Java (including Yogyakarta), East Java, and Central Sulawesi (Gardiner, 2007).…”