Malaysian Tropical Rain Forest Research Articles

Molecular Phylogenetics and Phylogeography of Malaysian Mousedeer (Tragulus kanchil) Based on Mitochondrial DNA Sequences of the D-Loop Region

Two sympatric mousedeer species, Tragulus kanchil and Tragulus napu, inhabit the Malaysian tropical rainforests. Previous studies have established their phylogenetic relationships based on morphological variations; however, comprehensive genetic data have yet to be extensively used to relate the relationships especially from different populations. The main objectives of this study were to determine the phylogenetic relationships, population genetics, and phylogeography of mousedeer species based on DNA sequences of the mitochondrial D-loop region. DNA from 32 mousedeer samples, representing various populations in Malaysia, was sequenced and analyzed using Neighbor-Joining, Maximum Parsimony, and Bayesian Inference approaches. The phylogenetic analyses showed two main clades representing the populations of T. kanchil and T. napu. The results also showed that the T. kanchil populations in Borneo was separated from Peninsular Malaysia taxa in MP and BI phylogenetic tree. However, Borneo population was nested in east population of Peninsular Malaysia in NJ tree. In addition, the T. kanchil population in Peninsular Malaysia further separated into east and west coast populations of Titiwangsa Range. It was supported with finding in population genetic relation that showed relatively low levels among population. This is expected because some of the populations are isolated geographically. The divergence of these populations is likely due to the Titiwangsa Range which acts as a barrier separating the east and west Peninsular Malaysia populations, and the South China Sea separates the populations of Peninsular Malaysia and Borneo. Molecular clock tree reconstruction showed that the separation of T. kanchil and T. napu occurred around 17.11 million years ago (MYAs). Furthermore, the T. kanchil populations from the east and west Peninsular Malaysia showed a branching pattern from those of Borneo of about 11.04 and 9.14 MYAs, respectively. The results of this study increase our understanding of Malaysian mousedeer phylogeny and phylogeography.

Comparative Diversity of Bats in Two Contrasting Habitats in Terengganu

Differentiations in the habitat and resource utilisation lead to segregation and specialisation of niches for bats within the structurally complex tropical rainforest in Malaysia. This research aims to characterise chiropterans’ assemblages found in two different habitat types in Tasik Kenyir (dipterocarp forest) and Setiu (oil palm plantation). A total of 48 sampling nights were conducted within two years period from March 2017 to March 2019 which covered four sampling sites in Tasik Kenyir and four sites at Setiu. Two standard four-bank harp traps and 10 mist nets were deployed throughout the study at every site to capture bats at understory levels. This makes a total of 576 sampling efforts for both areas. Song Meter SM2bats and Echo Meter Touch from Wildlife Acoustic were used to record the echolocation of insectivorous bats. The total number of individuals and species observed were used to determine species diversity, richness, and evenness. Paleontological statistic software was used to generate the rank abundance and species accumulation curves. Bray-Curtis similarity index was used to generalise the index that represents the relative abundance of the sampling sites. A total of 835 individuals comprising 31 species from six families were captured at both study areas. Out of 835 individuals, 695 were captured within Tasik Kenyir comprising 27 species from six families (H = 2.381) while 140 individuals were captured in Setiu comprising 20 species from five families (H = 2.40). The diversity of bats in Tasik Kenyir was hypothesised to be higher than in Setiu as the habitat possess a larger undisturbed forest. However, the result showed the opposite in which no significant difference was detected from the diversity index calculated between these two areas. Detailed studies need to be conducted to determine if some areas are used as transient habitats for bats.

A Walk Though the Rain Forest by Martin Jenkins

Reviewed by: A Walk Though the Rain Forest by Martin Jenkins Elizabeth Bush Jenkins, Martin A Walk Though the Rain Forest; illus. by Vicky White. Candlewick, 2022 [48p] Trade ed. ISBN 9781536211207 $18.99 Reviewed from digital galleys R 5-8 yrs Considering the forest here is the Taman Negara tropical rainforest in Malaysia, the titular walk promises to be an intriguing one. Readers know a lot of animals [End Page 51] live here, and Jenkins can enumerate a great many of them: "Ten kinds of owls, nine kinds of hornbills, eighteen kinds of woodpeckers." Some, however, he can't: "Goodness knows how many kinds of beetles (I certainly don't)." Those animals, spread out and well hidden, aren't easy to spot, so observers have to listen rather than simply look when carefully studying the trees. Jenkins highlights a puzzle: "All the trees here are big and old. There are no small, young ones." So, how does the rainforest keep itself going? The focus turns now to gathering clues: a fig tree where lots of animals feast; fig seeds broken open on the ground; trees too dense to admit much sunlight; piles of animal poop in a clearing; seeds in the poop; nutrients in the poop: "This is how it works: … When the animals poop, with luck they'll poop out some seeds somewhere good to grow." Jenkins' easy, conversational tone, and White's stunningly photorealistic paint and pencil mise en scène transform the shadowy, unfamiliar rainforest into an inviting milieu—wondrous but not too mysterious for a primary schooler to begin to grasp. A map, supplemental information, thumbnails of animals lurking in the illustrations, an index, and a brief resource list are included. Copyright © 2022 The Board of Trustees of the University of Illinois

Salt-lick use in Malaysian tropical rainforests reveals behavioral differences by food habit in medium and large-sized mammals

Salt-lick use in Malaysian tropical rainforests reveals behavioral differences by food habit in medium and large-sized mammals

Aerobic Methanotrophy and Co-occurrence Networks of a Tropical Rainforest and Oil Palm Plantations in Malaysia

Oil palm (OP) plantations are gradually replacing tropical rainforest in Malaysia, one of the largest palm oil producers globally. Conversion of lands to OP plantations has been associated with compositional shifts of the microbial community, with consequences on the greenhouse gas (GHG) emissions. While the impact of the change in land use has recently been investigated for microorganisms involved in N2O emission, the response of the aerobic methanotrophs to OP agriculture remains to be determined. Here, we monitored the bacterial community composition, focusing on the aerobic methanotrophs, in OP agricultural soils since 2012, 2006, and 1993, as well as in a tropical rainforest, in 2019 and 2020. High-affinity methane uptake was confirmed, showing significantly lower rates in the OP plantations than in the tropical rainforest, but values increased with continuous OP agriculture. The bacterial, including the methanotrophic community composition, was modified with ongoing OP agriculture. The methanotrophic community composition was predominantly composed of unclassified methanotrophs, with the canonical (Methylocystis) and putative methanotrophs thought to catalyze high-affinity methane oxidation present at higher relative abundance in the oldest OP plantation. Results suggest that the methanotrophic community was relatively more stable within each site, exhibiting less temporal variations than the total bacterial community. Uncharacteristically, a 16S rRNA gene-based co-occurrence network analysis revealed a more complex and connected community in the OP agricultural soil, which may influence the resilience of the bacterial community to disturbances. Overall, we provide a first insight into the ecology and role of the aerobic methanotrophs as a methane sink in OP agricultural soils.

Physical factors at salt licks influenced the frequency of wildlife visitation in the Malaysian tropical rainforest

Mineral reservoirs or salt licks are commonly used by wildlife to regulate the concentration of salt and minerals in their bodies. Salt lick utilisation is known to be influenced by the chemical composition, but information on their physical properties, particularly vegetation surrounding the salt licks is scarce. In this study, physical factors and wildlife utilisation at two natural salt licks (SPU and SPS) located in Perak, Malaysia, were determined. Wildlife visitation data were retrieved from camera traps. SPU exhibits two reservoirs represented by rocky and clay substrate, with minimally dense vegetation dominated by hardwood species and climbers. SPS encompasses muddy topsoil, open canopy cover, with highly dense forest floor vegetation. The wildlife survey shows a higher frequency of visitation in SPS, especially by ungulates, potentially due to dense understorey foliage that provides foraging sites for these animals. SPU exhibits more diverse but less frequent wildlife species, particularly primates, carnivores, and avian groups. High emergence and closed canopy cover at this lick serve as perching sites for primates and birds, while less dense understory vegetation could aid in prey detection among carnivore. Regardless of their physical assemblages, salt licks are an essential local hotspot for wildlife, therefore, elucidating the need to prioritise conservation areas by maximising the complementarities of salt licks.

Sensitivity of stomatal conductance to vapor pressure deficit and its dependence on leaf water relations and wood anatomy in nine canopy tree species in a Malaysian wet tropical rainforest

Canopy tree species with a large mean xylem vessel diameter has a high sensitivity of stomatal conductance to vapor pressure deficit in a wet tropical rainforest in Malaysia. We investigated the diurnal variation of stomatal conductance to water vapor (gs) and leaf water relations in nine tropical rainforest canopy tree species in Malaysia to investigate the sensitivity of stomatal conductance to VPD and its dependence on leaf water relations. We focused on the effect of wood anatomical properties on the stomatal sensitivity to VPD. Negative correlations were obtained between leaf-to-air VPD (VPDleaf) and gs for all species, in which interspecific variation was obtained for the sensitivity of gs to VPDleaf with the range of VPDleaf being 1.2–5.9 kPa. The species with large mean xylem vessel diameter had high sensitivity of gs to VPDleaf. Although significant variations were obtained among the species for leaf water relations, such as relative water content at the turgor loss point (RWCtlp) and water potential at the turgor loss point (Ψtlp), these water relations were not related to the stomatal sensitivity to VPDleaf. In the wet tropical forest in the present study, VPDleaf was the main regulator of gs in the nine tree species. The high sensitivity of gs to VPDleaf in the trees with a large vessel area may contribute to the maintenance of an adequate leaf water status, e.g., high levels of Ψleaf, throughout the day, across a period of varying air temperature.

Estimation of Forest Variable and Aboveground Biomass using Terrestrial Laser Scanning in the Tropical Rainforest

Estimation of accurate forest variable is crucial for forest monitoring and quantifying forest aboveground biomass (AGB). The objective of this study was to estimate forest variables and AGB using the TLS data acquired over the tropical rainforest of Malaysia. Individual trees were detected using the manual detection method in the RiSCAN PRO software. An average tree detection rate of 99.55% was achieved from the 10 sample plots. Forest variables, including DBH and height, were measured from 10 circular sample plots in the field. The accuracy of diameter at breast height (DBH) of trees measured from TLS was validated using field DBH as reference. A root means square error (RMSE) of 1.37 cm (6.60%) was obtained for manually measured TLS DBH. Similarly, TLS-based tree height was validated using airborne laser scanner height as a reference and resulted in RMSE of 1.74 m (9.30%). Finally, AGB was calculated using the variables derived from the TLS data. The result has shown an R2 value of 0.98 and RMSE of 0.077 Mg for AGB calculated from TLS data. The result of this study confirmed that TLS can provide a very good estimation of forest variables and AGB in the tropical dense rainforest.

Effect of agroclimatic variability on land suitability for cultivating rubber (Hevea brasiliensis) and growth performance assessment in the tropical rainforest climate of Peninsular Malaysia

Climate change directly alters climate conditions and indirectly impacts land suitability for cultivating rubber. The Malaysian tropical rainforest climate with regular rainfall of about 2000–2500 mm per year and the average temperature of 26–28 °C provide a suitable condition for planting rubber commercially. There is doubt about how well rubber plants will perform in the future because of climate change. The main question of whether rubber is still appropriate for planting in Peninsular Malaysia must be answered conclusively as rubber requires an approximately 30 year investment in one cycle. This question is particularly relevant in Malaysia as its rubber production is dependent on smallholders. Smallholders contribute approximately 93% of natural rubber production and furthermore, 93% of the rubber land area in Malaysia is owned by smallholders. An agroclimatic map produced in this study will help smallholders in deciding whether to proceed with rubber or change to other valuable crops based on their specific location. In this study, we evaluate 21st century land suitability for cultivating rubber and assess its growth based on climatic data for the Historical (1970–2000), Early (2010–2040), Middle (2040–2070) and End (2070–2100) projections periods. We use the Hevea 1.0 static model for rubber tree modelling to calculate the agroclimatic indices and estimate 30 years’ of actual rubber growth (girth) for all study periods. We find that climate change is predicted to have a positive impact on rubber-suitability in tropical rainforest in Malaysia climates at least until 2100. The End period, where the precipitation and temperature are projected to experience significant increases, becomes more favourable to rubber. The Perak region shows the highest increase in estimated rubber growth in the Early, Middle, and End periods by 16.3%, 31.9% and 39.4%, respectively. Among all regions, Kelang is predicted to be the most suitable area to plant rubber during the Early period as it has a potential estimated girth of up to 94.5 cm. Meanwhile, Johor is predicted to be the best place to cultivate rubber during the Middle and End periods with growth estimations of 97 cm and 99.5 cm, respectively. We indicate that about 32% of existing planted rubber area in Peninsular Malaysia is in Class 6 of land suitability to cultivate rubber.

Assessment of Aboveground Biomass and Temperature in the Tropical Rainforest of Malaysia

The relation between tropical rainforest to the climate variability is very important. This research aims to determine the relationship between aboveground biomass which prefer tree in the tropical rainforest and surrounding temperature. Diameter at breast height (DBH) of ten tree species and surrounding temperature collected data were taken to measure the correlation between the two variables by using statistical test. Furthermore, forest biomass estimation is also important towards the assessment of the productivity, structure and forest condition. The analysis in this research shows that simple linear regression model can be used to predict the future value of DBH for each species. The findings may help the reduction of greenhouse gas emissions with proper conservation and sustainable management.

Rattan litter-collecting structures attract nest-building and defending ants

ABSTRACTRattan is an important climbing palm taxon in Malaysian tropical rain forests. Many rattan species have unique structures directly associated with certain ant species. In this study, four rattan species (Daemonorops lewisiana, Calamus castaneus, Daemonorops geniculata and Korthalsia scortechinii) were inspected and documented in a field survey concerning their relationships with several ant species. We noticed that two rattan species (D. lewisiana and C. castaneus) were more likely to be associated with ants compared to their neighbouring rattan (Plectomia griffithii). However, D. lewisiana and C. castaneus did not directly provide shelters for ant colonies, but possessed unique structures: upward-pointing spines and funnel-shaped leaves, which are equipped to collect more litter than P. griffithii. To test our litter collecting hypothesis, we measured the inclination of spines from the stem. Our results showed the presence of ant colonies in the litter-collecting rattans (D. lewisiana and C. castaneus), which was significantly higher compared to a non-litter-collecting rattan (P. griffithii). We propose a complex and novel type of adaptation (litter-collection and provision of nesting materials) for rattans, which promotes interactions between the rattan and ants through the arrangements of leaves, leaflets, and spines. In return, the rattan may benefit from ants’ services, such as protection, nutrient enhancement, and pollination.

Forest termites mitigate the effects of drought

Tropical Ecology In many tropical regions, where drought is predicted to become more frequent in the coming years, termites are key components of ecosystem function. Ashton et al. experimentally manipulated termite communities to quantify their role during the 2015–2016 “super El Nino” drought in a Malaysian tropical rainforest. Termite relative abundance more than doubled in control plots during drought, maintaining three major ecosystem processes: decomposition, nutrient heterogeneity, and moisture retention. Seedling mortality increased where termites were suppressed. Science , this issue p. [174][1] [1]: /lookup/doi/10.1126/science.aau9565

Stable isotope analysis reveals the importance of plant‐based diets for tropical ant‐mimicking spiders

AbstractAnt‐mimicking spiders are a well‐known example of Batesian mimicry. Earlier studies have proposed that plant‐based diets (e.g. extrafloral nectar) are an important food source for ant‐mimicking spiders. However, it is still unclear whether the plant‐based diets are a main food source or supplementary energy source to the spiders. To examine the feeding habits, we measured stable nitrogen and carbon isotope ratios (δ15N and δ13C) of ant‐mimicking spiders (six species of Myrmarachne; one species of Agorius, Salticidae; and two species of Corinnidae) collected from a tropical rain forest in Malaysia and a dry evergreen forest in Thailand. We also investigated the isotopic signatures of several ant species sampled from the two forests for comparison. In general, the ant‐mimicking spiders had relatively low δ15N values, which were comparable to those of the nectar‐feeding and omnivorous ants. The δ15N values of the ant‐mimicking spiders differed significantly among the species: some species (e.g. Myrmarachne sp. H and Myrmarachne sp. 2) showed δ15N values similar to those of the nectar‐feeding ants, whereas the δ15N values of others (e.g. Myrmarachne maxillosa and Myrmarachne malayana) were close to those of the omnivorous ants. The δ13C values of the ant‐mimicking spiders did not differ significantly among the species, but tended to be similar to those of the nectar‐ and honeydew‐feeding ants rather than the predatory ants. These results indicate that plant‐based diets are important for the nutrition of ant‐mimicking spiders and suggest that the importance would differ among the ant‐mimicking spider species.

Different cambial activities in response to climatic factors of three Malaysian rainforest Shorea species with different stem diameters

This study demonstrated that the cambial activities of three selected Shorea species with different stem diameters growing in a tropical rainforest in Malaysia responded differently to climatic factors. We investigated the cambial activities in Shorea leprosula, Shorea acuminata, and Shorea parvifolia trees with different stem diameters at breast height growing in a natural lowland dipterocarp rainforest in Malaysia. We collected and analyzed samples from the main trunks of selected trees in monthly intervals from March 2013 to April 2014. The cambium of the three Shorea species showed periods of active and less active growth in the humid forest. Selected trees with different stem diameters of the same and different species showed variation in rhythms of cambial activity (changes in the numbers of cambial and enlarging cell layers) at site with similar growing conditions. Monthly mean relative humidity and monthly mean vapour pressure deficit were important factors influencing the number of cambial cells of S. acuminata with larger stem diameter, and those of S. parvifolia with different stem diameters. Active cambium were detected in months with high relative humidity and low vapour pressure deficit in those trees. Total monthly precipitation had significant positive correlation with the cambial cells activities of S. parvifolia with different stem diameters, but no correlation with those of the other two species. The cambium of S. leprosula with smaller and larger stem diameters were found active throughout the year. We concluded that the three Shorea species examined with different stem diameters have different growth strategies and thus react differently to climatic factors.

The dual defensive strategy of Amorphophallus throughout its ontogeny

ABSTRACTAmorphophallus bufo is a rarely studied plant in Malaysian tropical rainforests. We measured the spectral reflectance of different developmental stages of A. bufo (seedlings, juveniles and adults), background soil/ debris and leaves from other neighboring plant species. Results show that the leaves of A. bufo seedling have a similar reflectance curve as the background soil and debris. Adults and juveniles of A. bufo are similar to other neighboring plants' leaf colors. We hypothesize that the cryptic coloration of A. bufo seedlings plays an important role in camouflage and that the numerous black spots on the surface of the petioles and rachises, may serve as a defensive mimicry against herbivores.

Effects of rainfall exclusion on leaf gas exchange traits and osmotic adjustment in mature canopy trees of Dryobalanops aromatica (Dipterocarpaceae) in a Malaysian tropical rain forest.

Climate change exposes vegetation to unusual levels of drought, risking a decline in productivity and an increase in mortality. It still remains unclear how trees and forests respond to such unusual drought, particularly Southeast Asian tropical rain forests. To understand leaf ecophysiological responses of tropical rain forest trees to soil drying, a rainfall exclusion experiment was conducted on mature canopy trees of Dryobalanops aromatica Gaertn.f. (Dipterocarpaceae) for 4 months in an aseasonal tropical rain forest in Sarawak, Malaysia. The rainfall was intercepted by using a soft vinyl chloride sheet. We compared the three control and three treatment trees with respect to leaf water use at the top of the crown, including stomatal conductance (gsmax), photosynthesis (Amax), leaf water potential (predawn: Ψpre; midday: Ψmid), leaf water potential at turgor loss point (πtlp), osmotic potential at full turgor (π100) and a bulk modulus of elasticity (ε). Measurements were taken using tree-tower and canopy-crane systems. During the experiment, the treatment trees suffered drought stress without evidence of canopy dieback in comparison with the control trees; e.g., Ψpre and Ψmid decreased with soil drying. Minimum values of Ψmid in the treatment trees decreased during the experiment, and were lower than πtlp in the control trees. However, the treatment trees also decreased their πtlp by osmotic adjustment, and the values were lower than the minimum values of their Ψmid. In addition, the treatment trees maintained gs and Amax especially in the morning, though at midday, values decreased to half those of the control trees. Decreasing leaf water potential by osmotic adjustment to maintain gs and Amax under soil drying in treatment trees was considered to represent anisohydric behavior. These results suggest that D. aromatica may have high leaf adaptability to drought by regulating leaf water consumption and maintaining turgor pressure to improve its leaf water relations.

Ecological distribution of leaf stomata and trichomes among tree species in a Malaysian lowland tropical rain forest.

The vertical structure of a tropical rain forest is complex and multilayered, with strong variation of micro-environment with height up to the canopy. We investigated the relation between morphological traits of leaf surfaces and tree ecological characteristics in a Malaysian tropical rain forest. The shapes and densities of stomata and trichomes on the abaxial leaf surfaces and their relation with leaf characteristics such as leaf area and leaf mass per area (LMA) were studied in 136 tree species in 35 families with different growth forms in the tropical moist forest. Leaf physiological properties were also measured in 50 canopy and emergent species. Most tree species had flat type (40.4%) or mound type (39.7%) stomata. In addition, 84 species (61.76%) in 22 families had trichomes, including those with glandular (17.65%) and non-glandular trichomes (44.11%). Most leaf characteristics significantly varied among the growth form types: species in canopy and emergent layers and canopy gap conditions had higher stomatal density, stomatal pore index (SPI), trichome density and LMA than species in understory and subcanopy layers, though the relation of phylogenetically independent contrasts to each characteristic was not statistically significant, except for leaf stomatal density, SPI and LMA. Intrinsic water use efficiency in canopy and emergent tree species with higher trichome densities was greater than in species with lower trichome densities. These results suggest that tree species in tropical rain forests adapt to a spatial difference in their growth forms, which are considerably affected by phylogenetic context, by having different stomatal and trichome shapes and/or densities.

Estimating recharge based on long-term groundwater table fluctuation monitoring in a shallow aquifer of Malaysian tropical rainforest catchment

A practical and reliable approach was applied to investigate the groundwater dynamics and obtain natural direct recharge based on the time series of water table fluctuation in moderately flat coastal area with a shallow water table and tropical rainforest weather. Drainage rate was about 0.034 m/day in the study area as estimated by falling groundwater table in period of no rainfall and specific yield values ranged between 0.11 and 0.23 by calculating depth-dependent specific yield based on soil water storage for layering soils. The method was applied to the monthly data of shallow aquifer at eight field sites in north Kelantan river catchment in the period of 1991–2011. The cross-correlation and partial cross-correlation reveal the acceptable correlation between the water table fluctuation and the rainfall data assuming the time lag from precipitation to water table response is negligible due to shallow water table. Recharge rates vary with the field sites and mainly depend on soil type and rainfall rather than surface geology. Although computer simulation (with MRCR code) was implemented with limited data (two series), still results are just slightly greater than the field data which indicated the method successfully employed and can be applied in areas with similar conditions in future.

Leaf water use in heterobaric and homobaric leafed canopy tree species in a Malaysian tropical rain forest

Tropical canopy tree species can be classified into two types by their heterobaric and homobaric leaves. We studied the relation between both leaf types and their water use, together with the morphological characteristics of leaves and xylem, in 23 canopy species in a tropical rain forest. The maximum rates of photosynthesis and transpiration were significantly higher in heterobaric leaf species, which also underwent larger diurnal variations of leaf water potential compared to homobaric leaf species. The vessel diameter was significantly larger and the stomatal pore index (SPI) was significantly higher in heterobaric than that in homobaric leaf species. There was a significant positive correlation between the vessel diameter, SPI, and maximum transpiration rates in all the studied species of both leaf types. However, there was no significant difference in other properties, such as leaf water-use efficiency, leaf mass per area, leaf nitrogen content, and leaf δ13C between heterobaric and homobaric leaf species. Our results indicate that leaf and xylem morphological differences between heterobaric and homobaric leaf species are closely related to leaf water-use characteristics, even in the same habitat: heterobaric leaf species achieved a high carbon gain with large water use under strong light conditions, whereas homobaric leaf species can maintain a high leaf water potential even at midday as a result of low water use in the canopy environment.

Understanding the Quorum-Sensing Bacterium Pantoea stewartii Strain M009 with Whole-Genome Sequencing Analysis

Pantoea stewartii is known to be the causative agent of Stewart’s wilt, which usually affects sweet corn (Zea mays) with the corn flea beetle as the transmission vector. In this work, we present the whole-genome sequence of Pantoea stewartii strain M009, isolated from a Malaysian tropical rainforest waterfall.