Abstract
Collabieae (Orchidaceae) is a long neglected tribe with confusing tribal and generic delimitation and little-understood phylogenetic relationships. Using plastid matK, psaB, rbcL, and trnH-psbA DNA sequences and morphological evidence, the phylogenetic relationships within the tribe Collabieae were assessed as a basis for revising their tribal and generic delimitation. Collabieae (including the previously misplaced mycoheterotrophic Risleya) is supported as monophyletic and nested within a superclade that also includes Epidendreae, Podochileae, Cymbidieae and Vandeae. Risleya is nested in Collabiinae and sister to Chrysoglossum, a relationship which, despite their great vegetative differences, is supported by floral characters. Ania is a distinct genus supported by both morphological and molecular evidence, while redefined Tainia includes Nephelaphyllum and Mischobulbum. Calanthe is paraphyletic and consists four clades; the genera Gastrorchis, Phaius and Cephalantheropsis should be subsumed within Calanthe. Calanthe sect. Ghiesbreghtia is nested within sect. Calanthe, to which the disputed Calanthe delavayi belongs as well. Our results indicate that, in Collabieae, habit evolved from being epiphytic to terrestrial.
Highlights
The family of Orchidaceae is one of largest among seed plants, and several classification systems have been proposed to reflect their phylogeny and evolution
In Collabieae, as in many orchids, relationships have been traditionally defined based on subjective assessments of morphological characters, and phylogenetic relationships remain to be assessed using molecular data
Tribe Collabieae, described by Pfitzer [17] based on Collabium, is a medium-sized group with about 450–500 species distributed mainly in the Old World tropics with a few species extending into North Temperate Asia and Mesoamerica [18,19,20,21]
Summary
The family of Orchidaceae is one of largest among seed plants, and several classification systems have been proposed to reflect their phylogeny and evolution (such as [1,2,3,4]). Recent molecular phylogenetic studies have shed new light on the relationships of Orchidaceae from genera to subfamilies (such as [5,6,7,8,9,10,11,12,13,14,15,16]). In Collabieae, as in many orchids, relationships have been traditionally defined based on subjective assessments of morphological characters, and phylogenetic relationships remain to be assessed using molecular data. Schlechter [22] established two subtribes, Collabiinae and Phajinae, in the tribe Kerosphaereae. The former included 7 genera, viz., Chrysoglossum, Collabium, Diglyphosa, Mischobulbum, Nephelaphyllum, Pilophyllum, and Tainia, while the latter included
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