Phylogenetic and systematic studies of the schismatoglottideae (araceae: aroideae)

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Date
2009
Authors
Wong, Sin Yeng
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Abstract
The tribe Schismatoglottideae is the most diverse aroid taxon in Borneo, comprising in excess of 100 species of which over 95% are endemic. Besides Schismatoglottis Zoll. & Moritzi, the largest genus within the tribe, the tribe includes four small satellite genera, Aridarum Ridl., Bucephalandra Schott, Phymatarum M. Hotta dan Piptospatha N.E. Br. that are endemic to Borneo, except the last which extends to the Malay Peninsular and Southern Peninsular Thailand. Recent and ongoing research of the Schismatoglottideae includes alpha-taxonomy, phenological and ecological studies have provided a stable species platform from which to describe the considerable novelties still known to exist, and from which to test hypotheses of infra-tribal, and intergeneric phylogenetic processes. In addition, considerable research remains to be done to resolve generic boundaries within the tribe. This study was carried out to: (1) undertake extensive field studies including vouchering of sampled populations belonging to tribe Schismatoglottideae; (2) resolve by use of molecular methodologies the internal phylogeny of the tribe using molecular methodologies; (3) investigate, by field and laboratory observations on inflorescence morphology, pollination, dispersal and seedling establishment processes, and by mapping relevant features onto phylogenetic trees to produce an hypothesis of the evolution of these adaptations. A combined molecular phylogenetic analysis of matK, the 3' portion of the trnK intron, and trnL-F DNA sequence data was carried out on 78 taxa representing all genera in the tribe, all informal groups in Schismatoglottis, together with sister tribe Cryptocoryneae, and outgroups from Araceae. Analyses of combined DNA datasets with parsimony, maximum likelihood, and Bayesian methods revealed tribe Schismatoglottideae to be a polyphyletic assemblege. Neotropical Schismatoglottis is shown to be sister to the palaeotropical Schismatoglottideae + Crytocoryneae. Schismatoglottis acuminatissima is a sister clade to the rest of the Schismatoglottideae. Palaeotropical Schismatoglottis is unsupported as a monophyletic genus. A new neotropical tribe of Araceae: Aroideae, Philonotieae S.Y. Wong & P.C. Boyce, is proposed. Philonotieae is sister to Crytocoryneae + palaeotropical Schismatoglottideae, with these three tribes comprising the schismatoglottid alliance. Apoballis, Hestia, Pichinia and Schottarum are removed from Schismatoglottis sensu stricto into separate genera. Bakoa and Ooia are removed from Piptospatha, proposed as new genera. The morphological characters that facilitate rheophytism are: (1) Ability for shoot/root disarticulation; (2) Free ligular sheath soon becoming marcescent; (3) Presence of micropylar appendage and, (4) Presence of splash cup.
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PhD
Keywords
Biological Science , Phylogenetic , Schismatoglottideae
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