MyMedR

Displaying publications 81 - 100 of 362 in total

Abstract:

Sort:

Spatial patterns in the distribution of tropical tree species

Condit R, Ashton PS, Baker P, Bunyavejchewin S, Gunatilleke S, Gunatilleke N, et al.

Science, 2000 May 26;288(5470):1414-8.
PMID: 10827950

Fully mapped tree census plots of large area, 25 to 52 hectares, have now been completed at six different sites in tropical forests, including dry deciduous to wet evergreen forest on two continents. One of the main goals of these plots has been to evaluate spatial patterns in tropical tree populations. Here the degree of aggregation in the distribution of 1768 tree species is examined based on the average density of conspecific trees in circular neighborhoods around each tree. When all individuals larger than 1 centimeter in stem diameter were included, nearly every species was more aggregated than a random distribution. Considering only larger trees (>/= 10 centimeters in diameter), the pattern persisted, with most species being more aggregated than random. Rare species were more aggregated than common species. All six forests were very similar in all the particulars of these results.

Matched MeSH terms: Tropical Climate
Spatial distribution of the basidiocarps of aphyllophoraceous fungi in a tropical rainforest on Borneo Island, Malaysia

Yamashita S, Hattori T, Ohkubo T, Nakashizuka T

Mycol. Res., 2009 Oct;113(Pt 10):1200-7.
PMID: 19682573 DOI: 10.1016/j.mycres.2009.08.004

The spatial distribution of basidiocarps provides much information on the dispersal abilities, habitat preferences, and inter- and intraspecific interactions of aphyllophoraceous fungi. To reveal the spatial distribution and resource utilization patterns of aphyllophoraceous fungi in Malaysia, we conducted field observations in a primary forest in 2006 and analyzed the relationships between the abundance of eight dominant fungal species and various environmental factors. The topographical characteristics were significantly patchily distributed at the 100-m scale, whereas woody debris and most fungal species were distributed randomly. Although the dominant fungal species differed among the decay classes and diameters of the woody debris, the abundance of a few dominant species was significantly correlated with environmental factors. Although the latter factors might affect the spatial distribution of these fungi, the effects appear to be so small that they would not create an aggregated distribution at a few 100-m scales.

Matched MeSH terms: Tropical Climate
Fulltext Spatial and temporal behavioural responses of wild cattle to tropical forest degradation

Gardner PC, Goossens B, Goon Ee Wern J, Kretzschmar P, Bohm T, Vaughan IP

PLoS One, 2018;13(4):e0195444.
PMID: 29649279 DOI: 10.1371/journal.pone.0195444

Identifying the consequences of tropical forest degradation is essential to mitigate its effects upon forest fauna. Large forest-dwelling mammals are often highly sensitive to environmental perturbation through processes such as fragmentation, simplification of habitat structure, and abiotic changes including increased temperatures where the canopy is cleared. Whilst previous work has focused upon species richness and rarity in logged forest, few look at spatial and temporal behavioural responses to forest degradation. Using camera traps, we explored the relationships between diel activity, behavioural expression, habitat use and ambient temperature to understand how the wild free-ranging Bornean banteng (Bos javanicus lowi) respond to logging and regeneration. Three secondary forests in Sabah, Malaysian Borneo were studied, varying in the time since last logging (6-23 years). A combination of generalised linear mixed models and generalised linear models were constructed using >36,000 trap-nights. Temperature had no significant effect on activity, however it varied markedly between forests, with the period of intense heat shortening as forest regeneration increased over the years. Bantengs regulated activity, with a reduction during the wet season in the most degraded forest (z = -2.6, Std. Error = 0.13, p = 0.01), and reductions during midday hours in forest with limited regeneration, however after >20 years of regrowth, activity was more consistent throughout the day. Foraging and use of open canopy areas dominated the activity budget when regeneration was limited. As regeneration advanced, this was replaced by greater investment in travelling and using a closed canopy. Forest degradation modifies the ambient temperature, and positively influences flooding and habitat availability during the wet season. Retention of a mosaic of mature forest patches within commercial forests could minimise these effects and also provide refuge, which is key to heat dissipation and the prevention of thermal stress, whilst retention of degraded forest could provide forage.

Matched MeSH terms: Tropical Climate*
Sources of sedimentary PAHs in tropical Asian waters: differentiation between pyrogenic and petrogenic sources by alkyl homolog abundance

Saha M, Togo A, Mizukawa K, Murakami M, Takada H, Zakaria MP, et al.

Mar Pollut Bull, 2009 Feb;58(2):189-200.
PMID: 19117577 DOI: 10.1016/j.marpolbul.2008.04.049

We collected surface sediment samples from 174 locations in India, Indonesia, Malaysia, Thailand, Vietnam, Cambodia, Laos, and the Philippines and analyzed them for polycyclic aromatic hydrocarbons (PAHs) and hopanes. PAHs were widely distributed in the sediments, with comparatively higher concentrations in urban areas (Sigma PAHs: approximately 1000 to approximately 100,000 ng/g-dry) than in rural areas ( approximately 10 to approximately 100g-dry), indicating large sources of PAHs in urban areas. To distinguish petrogenic and pyrogenic sources of PAHs, we calculated the ratios of alkyl PAHs to parent PAHs: methylphenanthrenes to phenanthrene (MP/P), methylpyrenes+methylfluoranthenes to pyrene+fluoranthene (MPy/Py), and methylchrysenes+methylbenz[a]anthracenes to chrysene+benz[a]anthracene (MC/C). Analysis of source materials (crude oil, automobile exhaust, and coal and wood combustion products) gave thresholds of MP/P=0.4, MPy/Py=0.5, and MC/C=1.0 for exclusive combustion origin. All the combustion product samples had the ratios of alkyl PAHs to parent PAHs below these threshold values. Contributions of petrogenic and pyrogenic sources to the sedimentary PAHs were uneven among the homologs: the phenanthrene series had a greater petrogenic contribution, whereas the chrysene series had a greater pyrogenic contribution. All the Indian sediments showed a strong pyrogenic signature with MP/P approximately 0.5, MPy/Py approximately 0.1, and MC/C approximately 0.2, together with depletion of hopanes indicating intensive inputs of combustion products of coal and/or wood, probably due to the heavy dependence on these fuels as sources of energy. In contrast, sedimentary PAHs from all other tropical Asian cities were abundant in alkylated PAHs with MP/P approximately 1-4, MPy/Py approximately 0.3-1, and MC/C approximately 0.2-1.0, suggesting a ubiquitous input of petrogenic PAHs. Petrogenic contributions to PAH homologs varied among the countries: largest in Malaysia whereas inferior in Laos. The higher abundance of alkylated PAHs together with constant hopane profiles suggests widespread inputs of automobile-derived petrogenic PAHs to Asian waters.

Matched MeSH terms: Tropical Climate*
Source apportionment and health risk assessment of PM10 in a naturally ventilated school in a tropical environment

Mohamad N, Latif MT, Khan MF

Ecotoxicol Environ Saf, 2016 Feb;124:351-362.
PMID: 26590697 DOI: 10.1016/j.ecoenv.2015.11.002

This study aimed to investigate the chemical composition and potential sources of PM10 as well as assess the potential health hazards it posed to school children. PM10 samples were taken from classrooms at a school in Kuala Lumpur's city centre (S1) and one in the suburban city of Putrajaya (S2) over a period of eight hours using a low volume sampler (LVS). The composition of the major ions and trace metals in PM10 were then analysed using ion chromatography (IC) and inductively coupled plasma-mass spectrometry (ICP-MS), respectively. The results showed that the average PM10 concentration inside the classroom at the city centre school (82µg/m(3)) was higher than that from the suburban school (77µg/m(3)). Principal component analysis-absolute principal component scores (PCA-APCS) revealed that road dust was the major source of indoor PM10 at both school in the city centre (36%) and the suburban location (55%). The total hazard quotient (HQ) calculated, based on the formula suggested by the United States Environmental Protection Agency (USEPA), was found to be slightly higher than the acceptable level of 1, indicating that inhalation exposure to particle-bound non-carcinogenic metals of PM10, particularly Cr exposure by children and adults occupying the school environment, was far from negligible.

Matched MeSH terms: Tropical Climate
Some nematodes and acanthocephalans from exotic ornamental freshwater fishes imported into Germany

Moravec F, Wolter J, Körting W

Folia Parasitol., 1999;46(4):296-310.
PMID: 10730202

Five species of adult nematodes, unidentifiable nematode larvae, and three species of acanthocephalans, were found in freshwater ornamental fishes newly imported into Germany from Brazil, Colombia, Indonesia, Malaysia, Nigeria, Peru, Sri Lanka and Thailand. The following species were identified: Adult Nematoda: Pseudocapillaria tomentosa, Capillariidae gen. sp., Dichelyne hartwichi sp. n., Procamallanus (Spirocamallanus) pintoi and Spinitectus allaeri; Acanthocephala: Pseudogorgorhynchus arii gen. et sp. n., Neoechinorhynchus sp. and Pallisentis sp. The nematode Dichelyne hartwichi sp. n. (male only) from the intestine of Chelonodon fluviatilis (Hamilton) from Thailand is characterised mainly by the presence of minute cuticular spines on the tail tip, length of spicules (510 microns) and arrangement of caudal papillae. The acanthocephalan Pseudogorgorhynchus arii sp. n. from the intestine of Ariopsis seemanni (Günther) from Colombia represents a new genus Pseudogorgorhynchus gen. n., differing from other genera of the Rhadinorhynchidae mainly in possessing a small proboscis armed with markedly few (18) hooks arranged in six spiral rows. Spinitectus macheirus Boomker et Puylaert, 1994 and Spinitectus moraveci Boomker et Puylaert, 1994 are considered junior synonyms of Spinitectus allaeri Campana-Rouget, 1961.

Matched MeSH terms: Tropical Climate
Some impressions of childbearing in tropical areas. II. Pre-eclampsia and low birthweight

Thompson B, Baird D

J Obstet Gynaecol Br Commonw, 1967 Aug;74(4):499-509.
PMID: 6033270
Matched MeSH terms: Tropical Climate*
Some impressions of childbearing in tropical areas. 3. Outcome of labour

Thompson B, Baird D

J Obstet Gynaecol Br Commonw, 1967 Aug;74(4):510-22.
PMID: 6033271
Matched MeSH terms: Tropical Climate*
Some aspects of dentistry in Sabah

Golding KM

Aust Dent J, 1971 Dec;16(6):389-93.
PMID: 5291233
Matched MeSH terms: Tropical Climate
Fulltext Soils on exposed Sunda shelf shaped biogeographic patterns in the equatorial forests of Southeast Asia

Slik JW, Aiba S, Bastian M, Brearley FQ, Cannon CH, Eichhorn KA, et al.

Proc Natl Acad Sci U S A, 2011 Jul 26;108(30):12343-7.
PMID: 21746913 DOI: 10.1073/pnas.1103353108

The marked biogeographic difference between western (Malay Peninsula and Sumatra) and eastern (Borneo) Sundaland is surprising given the long time that these areas have formed a single landmass. A dispersal barrier in the form of a dry savanna corridor during glacial maxima has been proposed to explain this disparity. However, the short duration of these dry savanna conditions make it an unlikely sole cause for the biogeographic pattern. An additional explanation might be related to the coarse sandy soils of central Sundaland. To test these two nonexclusive hypotheses, we performed a floristic cluster analysis based on 111 tree inventories from Peninsular Malaysia, Sumatra, and Borneo. We then identified the indicator genera for clusters that crossed the central Sundaland biogeographic boundary and those that did not cross and tested whether drought and coarse-soil tolerance of the indicator genera differed between them. We found 11 terminal floristic clusters, 10 occurring in Borneo, 5 in Sumatra, and 3 in Peninsular Malaysia. Indicator taxa of clusters that occurred across Sundaland had significantly higher coarse-soil tolerance than did those from clusters that occurred east or west of central Sundaland. For drought tolerance, no such pattern was detected. These results strongly suggest that exposed sandy sea-bed soils acted as a dispersal barrier in central Sundaland. However, we could not confirm the presence of a savanna corridor. This finding makes it clear that proposed biogeographic explanations for plant and animal distributions within Sundaland, including possible migration routes for early humans, need to be reevaluated.

Matched MeSH terms: Tropical Climate
Fulltext Soil nitrogen concentration mediates the relationship between leguminous trees and neighbor diversity in tropical forests

Xu H, Detto M, Fang S, Chazdon RL, Li Y, Hau BCH, et al.

Commun Biol, 2020 06 19;3(1):317.
PMID: 32561898 DOI: 10.1038/s42003-020-1041-y

Legumes provide an essential service to ecosystems by capturing nitrogen from the atmosphere and delivering it to the soil, where it may then be available to other plants. However, this facilitation by legumes has not been widely studied in global tropical forests. Demographic data from 11 large forest plots (16-60 ha) ranging from 5.25° S to 29.25° N latitude show that within forests, leguminous trees have a larger effect on neighbor diversity than non-legumes. Where soil nitrogen is high, most legume species have higher neighbor diversity than non-legumes. Where soil nitrogen is low, most legumes have lower neighbor diversity than non-legumes. No facilitation effect on neighbor basal area was observed in either high or low soil N conditions. The legume-soil nitrogen positive feedback that promotes tree diversity has both theoretical implications for understanding species coexistence in diverse forests, and practical implications for the utilization of legumes in forest restoration.

Matched MeSH terms: Tropical Climate
Soil microflora of plantations and natural rain forest of West Malaysia

Varghese G

Mycopathol Mycol Appl, 1972 Oct 09;48(1):43-61.
PMID: 4677628
Matched MeSH terms: Tropical Climate*
Size-related flowering and fecundity in the tropical canopy tree species, Shorea acuminata (Dipterocarpaceae) during two consecutive general flowerings

Naito Y, Kanzaki M, Numata S, Obayashi K, Konuma A, Nishimura S, et al.

J Plant Res, 2008 Jan;121(1):33-42.
PMID: 17943228

We monitored the reproductive status of all trees with diameters at breast height (dbh) >30 cm in a 40-ha plot at Pasoh, west Malaysia, and investigated the individual fecundity of 15 Shorea acuminata Dyer (Dipterocarpaceae) trees using seed-trapping methods during two consecutive general flowering periods in 2001 (GF2001) and 2002 (GF2002). The proportion of flowering trees was higher, and not dependent on size, in GF2002 (84.2%), than in GF2001 (54.5%), when flowering mainly occurred in trees with a dbh < or =70 cm. Fecundity parameters of individual trees per event varied widely (221,000-35,200,000 flowers, 0-139,000 mature seeds, and 1.04-177 kg total dry matter mass of fruit (TDM) per tree). Monotonic increases with increasing tree size were observed for flower production and TDM amongst trees up to 90 cm in dbh, but not for mature seed production or for any of these parameters amongst larger trees. The pattern of reproductive investment during the two consecutive reproductive events clearly differed between medium-sized and large trees; the former concentrated their reproductive investment in one of the reproductive events whereas the latter allocated their investment more evenly to both reproductive events. Our results suggest size-related differences in the resource allocation pattern for reproduction.

Matched MeSH terms: Tropical Climate
Size and shape of Kedah-Kelantan cows

Aman A, Brown CJ, Johnson Z

Growth, 1978 Dec;42(4):486-94.
PMID: 750311

Body weight and nine body measurements were recorded on 79 mature Kedah-Kelantan cows at two locations. The Kedah-Kelantan is an indigenous cattle of Malaysia. A principal component analysis was used to study size and shape as indicated by the dependence structure among measurements. The total variation among measurements associated with the first principal component which was interpreted as a measure of general size was 40.8%. The second principal component contrasted cows tall at the withers, and deep at the chest with top line sloping downward and under line sloping upward from front to rear with those having less wither height and chest depth and straighter lines. This contrast accounted for 14.3% of the variation in body dimensions. The third principal component contrasted long, narrow, and deeper cows with a more compact type. This contrast accounted for 10.7% of the variation in body dimensions.

Matched MeSH terms: Tropical Climate
Similar non-random processes maintain diversity in two tropical rainforests

Wills C, Condit R

Proc Biol Sci, 1999 Jul 22;266(1427):1445-52.
PMID: 10457617

Quadrat-based analysis of two rainforest plots of area 50 ha, one in Panama (Barro Colorado Island, BCI) and the other in Malaysia (Pasoh), shows that in both plots recruitment is in general negatively correlated with both numbers and biomass of adult trees of the same species in the same quadrat. At BCI, this effect is not significantly influenced by treefall gaps. In both plots, recruitment of individual species is negatively correlated with the numbers of trees of all species in the quadrats, but not with overall biomass. These observations suggest, but do not prove, widespread frequency-dependent effects produced by pathogens and seed-predators that act most effectively in quadrats crowded with trees. Within-species correlations of mortality with numbers or biomass are not found in either plot, indicating that most frequency-dependent mortality takes place before the trees reach 1 cm in diameter. Stochastic effects caused by BCI's more rapid tree turnover may contribute to a larger variance in diversity from quadrat to quadrat at BCI, although they are not sufficient to explain why BCI has fewer than half as many tree species as Pasoh. Finally, in both plots quadrats with low diversity show a significant increase in diversity over time, and this increase is stronger at BCI. This process, like the frequency-dependence, will tend to maintain diversity over time. In general, these non-random forces that should lead to the maintenance of diversity are slightly stronger at BCI, even though the BCI plot is less diverse than the Pasoh plot.

Matched MeSH terms: Tropical Climate
Significance of enteric gram-negative bacilli in the throat

Philpot CR, McDonald PJ, Chai KH

J Hyg (Lond), 1980 Oct;85(2):205-10.
PMID: 7005325

Pharyngeal micro-organisms of 131 Australian and Malaysian children and adults were compared by analysis of aerobic culture of throat swab specimens. Enteric Gram-negative bacilli were commonly isolated in small numbers from Malaysian adults whether they had sore throats (28%) or not (36%), but were detected in only 9% of Australian adults without sore throats and in only 12% and 4% of Malaysian children with and without sore throats respectively. In other respects microbiological findings were similar in the different groups of subjects studied. It is concluded that the pharyngeal carriage rate of enteric Gram-negative bacilli may differ substantially between different groups of normal individuals. Our findings also suggest that these micro-organisms do not have a pathogenic role in pharyngitis.

Matched MeSH terms: Tropical Climate
Sickle-cell trait in human biological and cultural evolution. Development of agriculture causing increased malaria is bound to gene-pool changes causing malaria reduction

Wiesenfeld SL

Science, 1967 Sep 08;157(3793):1134-40.
PMID: 6038684

The particular agricultural adaptation we have been considering is the ultimate determinant of the presence of malaria parasites in the intracellular environment of the human red blood cell. This change in the cellular environment is deleterious for normal individuals, but individuals with the sickle-cell gene are capable of changing their red-cell environment so that intense parasitism never develops. Normal individuals suffer higher mortality rates and lower fertility rates in a malarious environment than individuals with the sickle-cell trait do, so the latter contribute proportionately more people to succeeding generations.

Matched MeSH terms: Tropical Climate
Fulltext Shifting baselines on a tropical forest frontier: extirpations drive declines in local ecological knowledge

Kai Z, Woan TS, Jie L, Goodale E, Kitajima K, Bagchi R, et al.

PLoS One, 2014;9(1):e86598.
PMID: 24466163 DOI: 10.1371/journal.pone.0086598

The value of local ecological knowledge (LEK) to conservation is increasingly recognised, but LEK is being rapidly lost as indigenous livelihoods change. Biodiversity loss is also a driver of the loss of LEK, but quantitative study is lacking. In our study landscape in SW China, a large proportion of species have been extirpated. Hence, we were interested to understand whether species extirpation might have led to an erosion of LEK and the implications this might have for conservation. So we investigated peoples' ability to name a selection of birds and mammals in their local language from pictures. Age was correlated to frequency of forest visits as a teenager and is likely to be closely correlated to other known drivers of the loss of LEK, such as declining forest dependence. We found men were better at identifying birds overall and that older people were better able to identify birds to the species as compared to group levels (approximately equivalent to genus). The effect of age was also stronger among women. However, after controlling for these factors, species abundance was by far the most important parameter in determining peoples' ability to name birds. People were unable to name any locally extirpated birds at the species level. However, contrary to expectations, people were better able to identify extirpated mammals at the species level than extant ones. However, extirpated mammals tend to be more charismatic species and several respondents indicated they were only familiar with them through TV documentaries. Younger people today cannot experience the sights and sounds of forest animals that their parents grew up with and, consequently, knowledge of these species is passing from cultural memory. We suggest that engaging older members of the community and linking the preservation of LEK to biodiversity conservation may help generate support for conservation.

Matched MeSH terms: Tropical Climate
Fulltext Shared Signature of Recent Positive Selection on the TSBP1-BTNL2-HLA-DRA Genes in Five Native Populations from North Borneo

Hoh BP, Zhang X, Deng L, Yuan K, Yew CW, Saw WY, et al.

Genome Biol Evol, 2020 12 06;12(12):2245-2257.
PMID: 33022050 DOI: 10.1093/gbe/evaa207

North Borneo (NB) is home to more than 40 native populations. These natives are believed to have undergone local adaptation in response to environmental challenges such as the mosquito-abundant tropical rainforest. We attempted to trace the footprints of natural selection from the genomic data of NB native populations using a panel of ∼2.2 million genome-wide single nucleotide polymorphisms. As a result, an ∼13-kb haplotype in the Major Histocompatibility Complex Class II region encompassing candidate genes TSBP1-BTNL2-HLA-DRA was identified to be undergoing natural selection. This putative signature of positive selection is shared among the five NB populations and is estimated to have arisen ∼5.5 thousand years (∼220 generations) ago, which coincides with the period of Austronesian expansion. Owing to the long history of endemic malaria in NB, the putative signature of positive selection is postulated to be driven by Plasmodium parasite infection. The findings of this study imply that despite high levels of genetic differentiation, the NB populations might have experienced similar local genetic adaptation resulting from stresses of the shared environment.

Matched MeSH terms: Tropical Climate
Severe upper airway obstruction in the tropics requiring intensive care

Chan PW, Goh A, Lum L

Pediatr Int, 2001 Feb;43(1):53-7.
PMID: 11208000

BACKGROUND: The clinical profile of severe upper airway obstruction, a challenging acute pediatric emergency, has not been extensively documented in the developing nations of the tropics.
METHODS: The diagnostic categories, severity of illness and outcome from 63 episodes of severe upper airway obstruction in 56 children admitted to the Pediatric Intensive Care Unit between January 1994 and December 1999 were reviewed. Outcome variables studied included requirement for ventilation, mortality and complications. Severity of illness was determined with the Pediatric Risk of Mortality (PRISM) II score.
RESULTS: Viral croup (29%) was the most common diagnosis, followed by mediastinal malignancy (13%), bacterial tracheitis (11%) and Pierre Robin syndrome (11%). There were no admissions for acute epiglottitis. Thirty episodes (48%) required ventilation for a median duration of 4.0 days. Bacterial tracheitis (100%) and subglottic stenosis (100%) were the most likely diagnoses requiring ventilation. Difficulty in intubation was encountered in 13 episodes (43%) involving, in particular, patients with bacterial tracheitis (83%; P = 0.006). Only two patients required a tracheostomy. The overall mortality was 11%. The PRISM score for all categories was generally low (mean 10.3 +/- 1.0; median 9.0). Non-survivors had a significantly higher PRISM II score than survivors (27.4 +/- 9.7 vs 8.1 +/- 4.9, respectively; P = 0.002) and were more likely to include children with bacterial tracheitis and mediastinal malignancy.
CONCLUSIONS: There is marked heterogeneity in the causes of upper airway obstruction in the tropics with viral croup remaining the most common. A significant proportion required ventilation, but outcome is generally favorable, except in those with bacterial tracheitis and mediastinal malignancy.

Matched MeSH terms: Tropical Climate

Filters

Please provide feedback to Administrator (afdal@afpm.org.my)

External Links