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Chen J.,National University of Singapore | Tan H.T.W.,National University of Singapore | Wong K.M.,Singapore Botanic Gardens
Plant Systematics and Evolution | Year: 2014

The significance of leaf micromorphology in distinguishing species and higher taxa has been well established in several plant groups, but has not been well studied in Timonius. This deserves some attention because (1) leaves are most commonly represented in herbarium specimens; (2) leaf micromorphology may facilitate the recognition of male and female specimens of the same species in dioecious taxa with sexually dimorphic inflorescences and flowers, such as Timonius, and (3) silvery lower leaf lamina surfaces occur in several Timonius species. The micromorphology of the lower lamina surface of 12 Timonius species was examined using scanning electron microscopy to establish the taxonomic utility of lower lamina micromorphology and to investigate if species with silvery leaf undersides share similar leaf micromorphological traits. For all Timonius species examined, the leaf hairs are unbranched and non-glandular. Hair morphology and density were found to be uniform within species but vary substantially between species. The silvery leaved species are typically characterised by one or more of the following leaf traits—long hair length, high hair density, and the presence of lanate hairs. Nevertheless, different combinations of these three traits result in much leaf micromorphological diversity, enabling distinction among the silvery leaved species based on leaf hair characters. © 2014, Springer-Verlag Wien.

Xi Z.,Harvard University | Bradley R.K.,Fred Hutchinson Cancer Research Center | Wurdack K.J.,Smithsonian Institution | Wong K.M.,Singapore Botanic Gardens | And 4 more authors.
BMC Genomics | Year: 2012

Background: Recent studies have shown that plant genomes have potentially undergone rampant horizontal gene transfer (HGT). In plant parasitic systems HGT appears to be facilitated by the intimate physical association between the parasite and its host. HGT in these systems has been invoked when a DNA sequence obtained from a parasite is placed phylogenetically very near to its host rather than with its closest relatives. Studies of HGT in parasitic plants have relied largely on the fortuitous discovery of gene phylogenies that indicate HGT, and no broad systematic search for HGT has been undertaken in parasitic systems where it is most expected to occur.Results: We analyzed the transcriptomes of the holoparasite Rafflesia cantleyi Solms-Laubach and its obligate host Tetrastigma rafflesiae Miq. using phylogenomic approaches. Our analyses show that several dozen actively transcribed genes, most of which appear to be encoded in the nuclear genome, are likely of host origin. We also find that hundreds of vertically inherited genes (VGT) in this parasitic plant exhibit codon usage properties that are more similar to its host than to its closest relatives.Conclusions: Our results establish for the first time a substantive number of HGTs in a plant host-parasite system. The elevated rate of unidirectional host-to- parasite gene transfer raises the possibility that HGTs may provide a fitness benefit to Rafflesia for maintaining these genes. Finally, a similar convergence in codon usage of VGTs has been shown in microbes with high HGT rates, which may help to explain the increase of HGTs in these parasitic plants. © 2012 Xi et al.; licensee BioMed Central Ltd.

Wijedasa L.S.,Singapore Botanic Gardens | Sloan S.,James Cook University | Michelakis D.G.,University of Edinburgh | Clements G.R.,Rimba | And 2 more authors.
Remote Sensing | Year: 2012

Landsat can be used to map tropical forest cover at 15-60 m resolution, which is helpful for detecting small but important perturbations in increasingly fragmented forests. However, among the remaining Landsat satellites, Landsat-5 no longer has global coverage and, since 2003, a mechanical fault in the Scan-Line Corrector (SLC-Off) of the Landsat-7 satellite resulted in a 22-25% data loss in each image. Such issues challenge the use of Landsat for wall-to-wall mapping of tropical forests, and encourage the use of alternative, spatially coarser imagery such as MODIS. Here, we describe and test an alternative method of post-classification compositing of Landsat images for mapping over 20.5 million hectares of peat swamp forest in the biodiversity hotspot of Sundaland. In order to reduce missing data to levels comparable to those prior to the SLC-Off error, we found that, for a combination of Landsat-5 images and SLC-off Landsat-7 images used to create a 2005 composite, 86% of the 58 scenes required one or two images, while 14% required three or more images. For a 2010 composite made using only SLC-Off Landsat-7 images, 64% of the scenes required one or two images and 36% required four or more images. Missing-data levels due to cloud cover and shadows in the pre SLC-Off composites (7.8% and 10.3% for 1990 and 2000 enhanced GeoCover mosaics) are comparable to the post SLC-Off composites (8.2% and 8.3% in the 2005 and 2010 composites). The area-weighted producer's accuracy for our 2000, 2005 and 2010 composites were 77%, 85% and 86% respectively. Overall, these results show that missing-data levels, classification accuracy, and geographic coverage of Landsat composites are comparable across a 20-year period despite the SLC-Off error since 2003. Correspondingly, Landsat still provides an appreciable utility for monitoring tropical forests, particularly in Sundaland's rapidly disappearing peat swamp forests. © 2012 by the authors.

Wong K.M.,Singapore Botanic Gardens | Low Y.W.,Singapore Botanic Gardens
Edinburgh Journal of Botany | Year: 2011

A description of the defining characteristics of Gardenia (Rubiaceae) and a revision of the Philippine species distinguished mainly by calyx morphology are presented. A key to five species of Gardenia recognised for the Philippines, full descriptions and illustrations, and a list of names which should be excluded from Gardenia are given. Relevant Philippine names for which holotypes were not indicated or have been destroyed are lectotypified. Two new endemic species, Gardenia ornata K.M.Wong and G. vulcanica K.M.Wong, are described. Gardenia elata Ridl. and G. mutabilis Reinw. ex Blume are newly applied to Philippine species previously enumerated under other names. Gardenia pseudopsidium (Blanco) Fern.-Vill. is considered a doubtful name, to which some authors have referred the endemic G. barnesii Merr. © 2011 Trustees of the Royal Botanic Garden Edinburgh.

Austin D.F.,Arizona Sonora Desert Museum | Staples G.,Singapore Botanic Gardens | Bianchini R.S.,Institute Botanica
Taxon | Year: 2014

Previous lectotypification of Ipomoea hederacea is shown to be ineffective. Here we discuss the situation and lectotypify the species with a specimen annotated by Jacquin. Ipomoea hederacea is not based on Convolvulus hederaceus L., since Jacquin was applying the name to a different taxon and therefore did not intend to publish a combination based on Convolvulus hederaceus. © International Association for Plant Taxonomy (IAPT) 2014.

Low Y.W.,Singapore Botanic Gardens
Systematic Botany | Year: 2013

Gardenia is an Old World genus of about 200 species. A bibliographic survey on Sulawesi Gardenia, a region extremely rich in plant diversity, but poorly explored botanically, enumerated five species, namely G. affinis, G. forsteniana, G. mutabilis, G. pelenkahuana, and G. vernicosa. Of these, G. mutabilis remains in Gardenia based on current generic delimitation using various morphological characters of the vegetative and floral parts. Three taxa, G. affinis, G. forsteniana, and G. pelenkahuana, have been reassigned to genera such as Porterandia or Rothmannia. Meanwhile, G. vernicosa was found to have been erroneously listed for Sulawesi. As herbarium materials labeled as G. mutabilis were examined and sorted, they were found to be heterogeneous and included two novelties, G. kabaenensis and G. longistipula, described and illustrated here. These two new taxa are distinguished from G. mutabilis based on calyx form and tube length, and stipule length. © 2013 by the American Society of Plant Taxonomists.

Kurzweil H.,Singapore Botanic Gardens
Nordic Journal of Botany | Year: 2010

A taxonomic review of the Thai species of the orchid genus Peristylus is presented. Seventeen species are recognised, five of them new to Thailand. Peristylus rigidus and P. phuwuaensis are endemic species, new to science, and the widespread P. maingayi and P. mannii have recently been newly recorded in the country. In addition, two further collections do not match any known Thai species, but very much resemble P. nematocaulon from the Himalayas and China. The present study will form the basis for the taxonomic account of Peristylus in the Flora of Thailand. © 2010 The Authors.

A review of the Thai species of the Calanthe group (Orchidaceae) is presented, based on the examination of over 500 herbarium and spirit specimens, and is a precursor for a later treatment in the Flora of Thailand. The group comprises the genera Calanthe R.Br., Phaius Lour. and Cephalantheropsis Guillaumin. In the genus Calanthe, 21 species are recognized, one of them being new but incompletely known as only a single flower was available for study. Calanthe angustifolia (Blume) Lindl. is newly reported for Thailand. Unusual forms of C. vestita Wall. ex Lindl. are commented on, and the extensive variation in the spur length of C. triplicata (Willemet) Ames is discussed. Five Phaius and one Cephalantheropsis species are recognized. Identification keys to the three genera and all species are given, and descriptions are provided for all species. A selection is illustrated by line drawings. © Publications Scientifi ques du Muséum national d'istoire naturelle, Paris.

Yam T.W.,Singapore Botanic Gardens | Chua J.,Singapore Botanic Gardens | Tay F.,Singapore Botanic Gardens | Ang P.,Singapore Botanic Gardens
Botanical Review | Year: 2010

Singapore is located near the equator, off the southern tip of the Malay Peninsula. The whole country consists mostly of lowland. It has many interesting types of natural habitats such as primary rain forest, freshwater swamp forest, mangroves, secondary forests, shrub, grasslands, and urban parks and fields. The climate is equatorial with relatively uniform temperature and high humidity. Unfortunately, many of the natural habitats and the native orchids which thrive there have disappeared due to habitat destruction. Some 226 species of native orchids have been recorded in Singapore. However, of these 178 are considered to be extinct, and only five are common. The orchid conservation programme aims to monitor existing species, explore ways to conserve their germplasm, and increase their numbers in natural, semi-natural, and urban environments through ex-situ seedling culture and subsequent re-introduction into appropriate habitats, including roadside trees, parks and natural areas. In the first phase of the programme, we have successfully propagated and carried out experiments of re-introduction on five species of native orchids, namely, Grammatophyllum speciosum, Bulbophyllum vaginatum, Bulbophyllum membranaceum, Cymbidium finlaysonianum and Cymbidium bicolor. Survival percentages 8-yr after the reintroduction events ranged from 10 to 95 for G. speciosum, the target species of the earliest re-introduction experiments. Size of the seedlings at reintroduction, host trees, and relative humidity seemed to play significant roles in the success rate of the reintroductions. © The New York Botanical Garden 2010.

Sugumaran M.,University of Malaya | Wong K.M.,Singapore Botanic Gardens
Plant Ecology and Evolution | Year: 2014

Background - Utania is a resurrected name for a monophyletic group previously placed as Fagraea section Racemosae, part of the Fagraea taxonomic complex, which currently includes five recognised genera. Methods - A revision of the genus in the Malay Peninsula was carried out using conventional methods of herbarium taxonomy. The specimen holdings of the K, KEP, KLU, L and SING herbaria were consulted. Results - Six species are recognised for Utania in the Malay Peninsula, including two new species, U. austromalayensis and U. nervosa. Three new combinations are made: U. maingayi, U. peninsularis and U. racemosa, the last for a species of Indo-China, Thailand, the Malay Peninsula and Sumatra, which does not extend to Borneo and eastwards. © 2014 Botanic Garden Meise and Royal Botanical Society of Belgium.

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