The sporogenesis and gametogenesis of Scyphiphora hydrophyllacea are described. The anther wall a... more The sporogenesis and gametogenesis of Scyphiphora hydrophyllacea are described. The anther wall at the microspore mother cell stage consists of a persistent epidermis, ephemeral endothecium, a middle-layer and a glandular tapetum which remains uninucleate throughout. The pollen grain is binucleate when shed. The ovule is anatropous, unitegmic and tenuinucellar with a poorly developed nucellus consisting of a single layer of cells. The primary archesporial cell (occasionally two) divides once to form the megaspore and a micropylar cell which degenerates. The megaspore divides three times to form the eight•nucleate embryo sac of the Allium type.
Decadal changes in urban bird abundance in Singapore
Birds are one of the most cost-effective groups to survey for monitoring human impacts on faunal ... more Birds are one of the most cost-effective groups to survey for monitoring human impacts on faunal communities and are consequently the best studied taxonomic group in urban areas. Urban bird assemblages are typically dominated by a few pest species, and need to be appropriately managed to reduce the aesthetic costs and health risks they may pose in highly-populated areas. Studies were conducted in Singapore (Feb.2000 to Feb.2001) to provide recommendations to manage urban birds, in particular to control the population of two invasive alien bird species: the house crow (Corvus splendens) and the Javan myna (Acridotheres javanicus). We then re-surveyed the same sites 9 years later (Mar.2010 to Feb.2011) to compare the changes in the abundance of the 20 most common urban bird species in Singapore over the past decade. We also tested whether the decrease in house crow abundance was correlated with increases in abundance of its co-invasive, the Javan myna, or with the Asian koel (Eudynamys scolopacea), a brood parasite of the house crow, across sites. In addition, we investigated competition between two myna species by comparing whether declines in the abundance of the common myna (Acridotheres trista) were correlated with increases in the abundance of the Javan myna. Our results showed that a total of 14 species recorded a signifi cant increase in abundance between the two surveys, two species signifi cantly decreased, and four species had no signifi cant change. There was also no signifi cant correlation between all the bird abundances, although changes in bird abundances were signifi cantly associated with certain changes in the urban environment such as spontaneous or cultivated green cover. We suggest that reduced density of house crow nests may actually result in increased vulnerability to, and hence success rate of, brood parasitism by the Asian koel, or there may be increased parasitism of other host species' nests. Meanwhile, competitive effects among the other birds may not be detectable at the scale of the transects used in our study.
novel derivative of sucrose, fl-(3,6-di-O-feruloyl)-fructofuranosyi-~-(2,3,4,6-tetra-O-acetyl)-gl... more novel derivative of sucrose, fl-(3,6-di-O-feruloyl)-fructofuranosyi-~-(2,3,4,6-tetra-O-acetyl)-glucopyranoside, was isolated from the wood of Bhesa paniculata. Its structure was determined by a combination of 2D t H-tH and t H-t 3C correlation NMR spectroscopy. The known compounds, glycerol 1-9', 12'-octadecadienoate,/~-sitosterol, (+)-pinoresinol, methyl 3,4-dihydroxybenzoate, 4-hydroxy-3-methoxybenzoic acid, anofinic acid and 2-(l'-methylethenyl)-benzofuran-5-carboxylic acid were also isolated.
Xanthone and Flavonoid Constituents ofGarcinia dulcis(Guttiferae)
Natural Product Letters, 1994
Abstract Extraction of the branches of Garcinia dulcis afforded a xanthone with a novel oxygenati... more Abstract Extraction of the branches of Garcinia dulcis afforded a xanthone with a novel oxygenation pattern [1, 4, 6-trihydroxy-5-methoxy-7-(3-methylbut-2-enyl) xanthone] in addition to the triterpenoid friedelin and the known flavonoids 3′-(3-methylbut-2-enyl) ...
Sun leaves from 37 species of tree and shrub were collected in four forest types on Pulau Ubin, S... more Sun leaves from 37 species of tree and shrub were collected in four forest types on Pulau Ubin, Singapore. Evidence of habitat-related variation in the form of leaves is presented. The species were from the habitats: mangrove, beach forest, adinandra belukar (secondary forest on degraded soils) and secondary forest on undegraded soils. The mangrove forest species sampled had thicker leaves with a lower specific leaf area than the beach forest species. Leaves of species from the adinandra belukar were thicker and smaller, with more dry weight per unit area, than those of pioneers from undegraded sites. This is interpreted as oligotrophic xeromorphy in adinandra belukar.
ABSTRACTClusters of four circular forest plots, 0.2 ha in total area, were inventoried for canopy... more ABSTRACTClusters of four circular forest plots, 0.2 ha in total area, were inventoried for canopy tree (≥30 cm gbh) and terrestrial herb floristic composition at 46 sites in the Central Catchment Nature Reserve, Singapore. The Nature Reserve covers a complex mosaic of lowland tropical forest of different successional stages, with much of the area covered in secondary forest 50–100 years old developed on exhausted agricultural soils. A total of 449 species of tree and 59 species of terrestrial herb were recorded from the clusters. Facultatively-terrestrial epiphytes were excluded from the analysis. Possible reasons for the low herb diversity are discussed. There was a marked similarity between ordinations (detrended correspondence analysis) of the clusters based on tree canopy composition weighted by species relative contribution to cluster total basal area and the herb flora composition, with a highly significant correlation between first axis scores of the two ordinations. Both ord...
Aim In general, the plant communities of oceanic islands suffer more from exotic plant invasions ... more Aim In general, the plant communities of oceanic islands suffer more from exotic plant invasions than their continental equivalents. At least part of this difference may be contributed by differences in non-biological factors, such as the antiquity and intensity of human impacts and the absence of internal barriers to dispersal, rather than differences in inherent invasibility. We tested the resistance of species-rich continental rain forests to plant invasion on a small, continental island that has been subject to prolonged and intensive human impact. Location Singapore is a 683-km 2 equatorial island <1 km from the Asian mainland and with a population of 4 million people. It has a continental biota but has been subject to human impacts as intense as on any oceanic island. Methods We sampled twenty-nine sites in seven vegetation types, ranging from urban wasteland to fragments of primary lowland rain forest. In each sample plot, all plant species were identified, exotic cover was estimated, and a range of environmental variables measured. Additional qualitative surveys for exotic invasion were made in other forest areas in Singapore. The data were analysed by Spearman's rank correlation coefficient. Results The number of exotic species recorded at a site was unrelated to the number of native species. Across all sites, percentage canopy opening had the highest correlation with the number of exotic species, while soil pH (which largely reflects the incorporation of calcareous construction wastes) had the highest correlation if the mangrove sites were excluded. There were no exotics in mangrove forest and only a tropical American, birddispersed shrub, Clidemia hirta (L.) D. Don (Melastomataceae: Koster's Curse), in primary and tall secondary forest patches. The species-poor early stages of woody plant succession on highly degraded soils were also very resistant to exotic plant invasion. Main conclusions Long-isolated rain forest fragments in an exotic-dominated continental island landscape resist invasion by exotic plants, suggesting that the problems on oceanic islands may reflect an inherently greater invasibility. This study also adds to the increasing evidence that the floras of tropical rain forest fragments in Southeast Asia are remarkably resilient on a timescale of decades to a century or more.
Factors affecting the distribution of vascular plants, springtails, butterflies and birds on small tropical islands
Journal of Biogeography, 2002
Aim The primary objective of our study was to examine the factors affecting the distribution of v... more Aim The primary objective of our study was to examine the factors affecting the distribution of vascular plants, springtails, butterflies and birds on small tropical islands to understand how different groups of organisms with distinct biological traits respond to biogeographical variables, such as island area.
An isolated 4-ha fragment of lowland tropical rain forest has been preserved in the Singapore Bot... more An isolated 4-ha fragment of lowland tropical rain forest has been preserved in the Singapore Botanic Gardens since their founding in 1859. The Botanic Gardens'Jungle has recently had enumerated all woody stems 5 cm diameter at breast height (dbh) and larger and the complete vascular plant flora inventoried. This inventory can be compared with the historic record of the flora of the Gardens'Jungle obtained from the extensive collection of herbarium specimens dating back to the 1890s. Of the 448 historically recorded native species, 220 are still present. Ninety-four native species for which there were no historic records and 80 introduced species were also recorded in the recent inventory. The 50.9% loss of plant species richness over approximately the last century has not been distributed uniformly across plant life-form groups. Tree species have been less likely to go extinct than shrubs, climbers, or epiphytes. But half of the tree species present in 1994 were represente d by only one or two individuals >-5 cm dbh and larger. Individual longevity may be the major correlate with persistence of plant species in isolated forest fragments. Shade-tolerant understory shrubs (mostly Rubiaceae) and rattans (Palmae) have been particularly prone to extinction. Some species have probably proliferated during the period of isolation. The tree Calophyllum ferrugineum currently constitutes one quarter of aU woody stems. A group of climbers has become very common and covers large areas, probably inhibiting tree regeneration. We conclude that tiny fragments will act as refuges for tropical rainforest plant species for decades, possibly even centuries after isolation but on their own they will not pro-• vide apermanentguarantee of the conservation of tropical biodiversity.
Vegetation Analysis, Leaf Structure and Nutrient Status of a Malaysian Health Community
Biotropica, 1995
A heath community found on Pulau Sibu, an island lying off the east coast of Peninsular Malaysia,... more A heath community found on Pulau Sibu, an island lying off the east coast of Peninsular Malaysia, was found to consist of a low scrub, generally under 2 m in height, containing 24 species of vascular plants growing on hills overlooking the sea. It grew on a very shallow and acidic (pH 4.3) soil that was low in total nitrogen concentration (0.2%). Leaves of the seven most common shrub species, Ixonanthes reticulata. Melastoma malabathricum, Rhodamnia cinerea, Rhodomyrtus tomentosa, Schima wallichii. Styphelia malayana and ...
Figure 10 from: Wong J, Foo M, Tan HTW, Meier R (2017) Whitefly predation and extensive mesonotum color polymorphism in an Acletoxenus population from Singapore (Diptera, Drosophilidae). ZooKeys 725: 49-69. https://doi.org/10.3897/zookeys.725.13675
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