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Climate change induced alterations to rainfall patterns have the potential to affect the regeneration dynamics of plant species, especially in historically everwet tropical rainforest. Differential species response to infrequent rainfall may influence seed germination and seedling establishment in turn affecting species distributions. We tested the role of watering frequency intervals (from daily to six-day watering) on the germination and the early growth of Dipterocarpaceae seedlings in Borneo. We used seeds that ranged in size from 500 to 20,000 mg in order to test the role of seed mass in mediating the effects of infrequent watering. With frequent rainfall, germination and seedling development traits bore no relationship to seed mass, but all metrics of seedling growth increased with increasing seed mass. Cumulative germination declined by 39.4% on average for all species when plants were watered at six-day intervals, and days to germination increased by 76.5% on average for all species from daily to six-day intervals. Final height and biomass declined on average in the six-day interval by 16% and 30%, respectively, but the percentage decrease in final size was greater for large-seeded species. Rooting depth per leaf area also significantly declined with seed mass indicating large-seeded species allocate relatively more biomass for leaf production. This difference in allocation provided an establishment advantage to large-seeded species when water was non-limiting but inhibited their growth under infrequent rainfall. The observed reduction in the growth of large-seeded species under infrequent rainfall would likely restrict their establishment in drier microsites associated with coarse sandy soils and ridge tops. In total, these species differences in germination and initial seedling growth indicates a possible niche axis that may help explain both current species distributions and future responses to climate change.

Dipterocarpus alatus belongs to Family Dipterocarpaceae that can be commonly found in Southeast Asian countries. It is a perennial plant with oval-shaped leaves and oleoresin-rich wood. It has been considered as a multipurpose plant since all parts can be practically utilized. One of the major problems for utilizing Dipterocarpus alatus is the difficulty knowing the exact age as this kind of plant is ready for multipurpose use after 20 years of age. At present, the most commonly used method for determining age of Dipterocarpus alatus is the annual ring estimation. However, this conventional method is unable to provide the high precision and accuracy of age determination due to its limitation including blurry annual rings caused by enriched oleoresin in the wood. The current study aimed to investigate the differences of 1 H -NMR spectroscopy-based metabolic profiles from bark and leaf of Dipterocarpus alatus at different ages including 2, 7, 15 and 25 years. Our findings demonstrated that there is a total of 56 metabolites shared between bark and leaf. It is noticeable that bark at different ages exhibited the strongest variation and sugar or sugar derivatives that were found in higher concentrations in bark compared with those in leaf. We found that decreasing levels of certain metabolites including tagatose, 1’kestose and 2’-fucosyllactose exhibited the promising patterns. In conclusion, panel metabolites involved in the sucrose biosynthesis can precisely determine the age and growth of Dipterocarpus alatus .

Dipterocarpaceae is one of the important timber families of Andaman Islands whose members were largely exploited for their timber in the past. The current study discusses in detail about the family Dipterocarpaceae of North Andaman forest with reference to its species composition, population structure and other ecological entities. Data was analyzed using various ecological and statistical methods. Dipterocarps were encountered in 97 plots, occupying 80% of the sampled area with 68 stems ha-1 and basal area of 8.2 m2 ha-1. Dipterocarpaceae ranked 3rd with reference to stem density (11%) and 1st with respect to basal area (18%). The family showed five species viz., Dipterocarpus alatus, D. costatus, D. gracilis, D. grandiflorus and Hopea odorata compounded from two genera - Dipterocarpus and Hopea. Keeping in view of the species demographic structure as well as regeneration status, conservative measures are suggested along with certain research questions which need immediate attention in the fragile insular ecosystems of Andaman Islands.

Relatively, little is known about the relationship between biodiversity and ecosystem functioning in forests, especially in the tropics. We describe the Sabah Biodiversity Experiment: a large-scale, long-term field study on the island of Borneo. The project aims at understanding the relationship between tree species diversity and the functioning of lowland dipterocarp rainforest during restoration following selective logging. The experiment is planned to run for several decades (from seed to adult tree), so here we focus on introducing the project and its experimental design and on assessing initial conditions and the potential for restoration of the structure and functioning of the study system, the Malua Forest Reserve. We estimate residual impacts 22 years after selective logging by comparison with an appropriate neighbouring area of primary forest in Danum Valley of similar conditions. There was no difference in the alpha or beta species diversity of transect plots in the two forest types, probably owing to the selective nature of the logging and potential effects of competitive release. However, despite equal total stem density, forest structure differed as expected with a deficit of large trees and a surfeit of saplings in selectively logged areas. These impacts on structure have the potential to influence ecosystem functioning. In particular, above-ground biomass and carbon pools in selectively logged areas were only 60 per cent of those in the primary forest even after 22 years of recovery. Our results establish the initial conditions for the Sabah Biodiversity Experiment and confirm the potential to accelerate restoration by using enrichment planting of dipterocarps to overcome recruitment limitation. What role dipterocarp diversity plays in restoration only will become clear with long-term results.

Summary Dipterocarpaceae are typical tropical plants (dipterocarp forests) that are famous for their high economic value because of their production of fragrant oleoresins, top‐quality timber and usage in traditional Chinese medicine. Currently, the lack of Dipterocarpaceae genomes has been a limiting factor to decipher the fragrant oleoresin biosynthesis and gain evolutionary insights into high‐quality wood formation in Dipterocarpaceae. We generated chromosome‐level genome assemblies for two representative Dipterocarpaceae species viz. Dipterocarpus turbinatus Gaertn. f. and Hopea hainanensis Merr. et Chun. Our whole‐genome duplication (WGD) analysis revealed that Dipterocarpaceae underwent a shared WGD event, which showed significant impacts on increased copy numbers of genes related to the biosynthesis of terpene, BAHD acyltransferases, fatty acid and benzenoid/phenylpropanoid, which probably confer to the formation of their characteristic fragrant oleoresin. Additionally, compared with common soft wood plants, the expansion of gene families was also found to be associated with wood formation, such as in CESA (cellulose synthase), CSLE (cellulose synthase‐like protein E), laccase and peroxidase in Dipterocarpaceae genomes, which might also contribute to the formation of harder, stronger and high‐density timbers. Finally, an integrative analysis on a combination of genomic, transcriptomic and metabolic data from different tissues provided further insights into the molecular basis of fragrant oleoresins biosynthesis and high‐quality wood formation of Dipterocarpaceae. Our study contributes the first two representative genomes for Dipterocarpaceae, which are valuable genetic resources for further researches on the fragrant oleoresins and superior‐quality timber, genome‐assisted breeding and improvement, and conservation biology of this family.

PREMISE OF THE STUDY: In tropical rainforests of Southeast Asia, a highly fecund thrips (Thrips spp.) responds rapidly to the mass flowering at multiple‐year intervals characteristic of certain species such as the canopy tree studied here, Shorea acuminata, by feeding on flower resources. However, past DNA analyses of pollen adherent to thrips bodies revealed that the thrips promoted a very high level of self‐pollination. Here, we identified the pollinator that contributes to cross‐pollination and discuss ways that the pollination system has adapted to mass flowering. METHODS: By comparing the patterns of floral visitation and levels of genetic diversity in adherent pollen loads among floral visitors, we evaluated the contribution of each flower visitor to pollination. KEY RESULTS: The big‐eyed bug, Geocoris sp., a major thrips predator, was an inadvertent pollinator, and importantly contributed to cross‐pollination. The total outcross pollen adhering to thrips was approximately 30% that on the big‐eyed bugs. Similarly, 63% of alleles examined in S. acuminata seeds and seedlings occurred in pollen adhering to big‐eyed bugs; about 30% was shared with pollen from thrips. CONCLUSIONS: During mass flowering, big‐eyed bugs likely travel among flowering S. acuminata trees, attracted by the abundant thrips. Floral visitation patterns of big‐eyed bugs vs. other insects suggest that these bugs can maintain their population size between flowering by preying upon another thrips (Haplothrips sp.) that inhabits stipules of S. acuminata throughout the year and quickly respond to mass flowering. Thus, thrips and big‐eyed bugs are essential components in the pollination of S. acuminata.

An ultrasound-assisted, one-pot cloud point extraction was developed for the determination of iron in vegetable samples by UV-Visible spectrophotometry. This method was based on the complexation of iron with an environmentally-friendly natural chelating agent extracted from Dipterocarpus intricatus Dyer fruit at pH 5.5 in the presence of Triton X-114. Reagent extraction, complexation, and preconcentration were performed simultaneously using ultrasound-assisted extraction at 45 °C. The surfactant-rich phase was diluted with ethanol and loaded through a syringe barrel packed with cotton that acted as a filter to trap the reagent powder. Analyte-entrapped on cotton was eluted using 0.1 mol·L[sup.−1] nitric acid solution. Filtrate and eluate solutions were measured absorbance of the dark-blue product at 575 nm. Influential parameters for the procedure were investigated. Under the optimum experimental conditions, the calibration curve was linear, ranging from 0.1 to 1.0 mg·L[sup.−1] with r[sup.2] = 0.997. Limits of detection and quantification were 0.03 and 0.09 mg·L[sup.−1], respectively while precision values of intra-day and inter-day were less than 5%. Recovery at 0.5 mg·L[sup.−1] ranged from 89.0 to 99.8%, while iron content in vegetable samples ranged from 2.45 to 13.36 mg/100 g. This method was cost-effective, reliable, eco-friendly, and convenient as a green analytical approach to determining iron content.

The rates of appearance of new mutations play a central role in evolution. However, mutational processes in natural environments and their relationship with growth rates are largely unknown, particular in tropical ecosystems with high biodiversity. Here, we examined the somatic mutation landscapes of two tropical trees, Shorea laevis (slow-growing) and S. leprosula (fast-growing), in central Borneo, Indonesia. Using newly constructed genomes, we identified a greater number of somatic mutations in tropical trees than in temperate trees. In both species, we observed a linear increase in the number of somatic mutations with physical distance between branches. However, we found that the rate of somatic mutation accumulation per meter of growth was 3.7-fold higher in S. laevis than in S. leprosula . This difference in the somatic mutation rate was scaled with the slower growth rate of S. laevis compared to S. leprosula, resulting in a constant somatic mutation rate per year between the two species. We also found that somatic mutations are neutral within an individual, but those mutations transmitted to the next generation are subject to purifying selection. These findings suggest that somatic mutations accumulate with absolute time and older trees have a greater contribution towards generating genetic variation.

Background Vatica guangxiensis , one of the northernmost dipterocarp tree species in Asian tropical rainforests and among the most critically endangered members of the Dipterocarpaceae, faces severe genetic risks due to its extremely small population size. Results We present a chromosome-scale genome assembly of V. guangxiensis , totaling 454.89 Mb, comprising 54 scaffolds (contig N50 = 38.11 Mb). To inform conservation strategies, we conducted a population genomic analysis involving 148 individuals from three natural populations of V. guangxiensis sensu lato and two of V. mangachapoi , a widely distributed tropical rainforest species in Asia. Our results clarified the population structure, interspecific differentiation, and species delimitation of V. guangxiensis sensu lato, resolving longstanding taxonomic ambiguities and supporting the reinstatement of the two Yunnan populations as V. xishuangbannaensis . Compared with V. xishuangbannaensis and V. mangachapoi , V. guangxiensis exhibits significantly lower genetic diversity, higher inbreeding, and an elevated mutation load. Additionally, we revealed a near-complete absence of gene flow with related species and documented historically low effective population sizes, underscoring its vulnerability to genome erosion. Notably, genomic comparisons between mature and regenerating individuals revealed a 26.45% decrease in genetic diversity and a 10.70% increase in mutation load in smaller trees of V. guangxiensis , reflecting accelerated genomic erosion during natural regeneration. Conclusions Our findings underscore the urgent need to monitor genomic health and implement effective conservation measures to safeguard V. guangxiensis . This study highlights the critical role of genomic data in assessing population health and informing strategies for the preservation of endangered species in marginal tropical rainforests.

Ectomycorrhizal (ECM) associations were historically considered rare or absent from tropical ecosystems. Although most tropical forests are dominated by arbuscular mycorrhizal (AM) trees, ECM associations are widespread and found in all tropical regions. Here, we highlight emerging patterns of ECM biogeography, diversity and ecosystem functions, identify knowledge gaps, and offer direction for future research. At the continental and regional scales, tropical ECM systems are highly diverse and vary widely in ECM plant and fungal abundance, diversity, composition and phylogenetic affinities. We found strong regional differences among the dominant host plant families, suggesting that biogeographical factors strongly influence tropical ECMsymbioses. BothECMplants and fungi also exhibit strong turnover along altitudinal and soil fertility gradients, suggesting niche differentiation among taxa. Ectomycorrhizal fungi are often more abundant and diverse in sites with nutrient-poor soils, suggesting that ECM associations can optimize plant nutrition and may contribute to the maintenance of tropical monodominant forests. More research is needed to elucidate the diversity patterns of ECM fungi and plants in the tropics and to clarify the role of this symbiosis in nutrient and carbon cycling.