Tropical Rain Forests Of Southeast Asia Research Articles

Using intraspecific molecular and phenotypic variation to promote multi-functionality of reforestation during climate change – A review of tropical forest case studies in South-east Asia

Abstract The study of intraspecific genetic variation in plant traits for use in tropical forest restoration has broad potential for increasing our ability to achieve multi-functional objectives during this era of climate change. Developing seed-sourcing guidelines that optimize phenotypic characteristics best suited to a particular planting site as well as to future conditions imposed by environmental change could be useful for effective reforestation. Because evolution operates differently across tree species, this is an especially cumbersome task in tropical forests that contain thousands of species. Partially due to this high plant diversity, research and application of intraspecific variation in genetics, plant traits, and plant function in tropical forests wane far behind less diverse forest biomes. To examine the potential for improving reforestation efforts in tropical forests by considering intraspecific variation in plant traits and functions, we review the state of knowledge on intraspecific variation in South-east Asia as a case study. We focus on the dipterocarp family ( Dipterocarpaceae ), a highly diverse family of 16 genera with approximately 695 known species that often dominate lowland tropical rainforests of South-east Asia with many of these forests in a degraded state and in need of restoration. We found that there is research accumulating to understand genetic variation in approximately 10% of these 695 species. Intraspecific molecular variation exists at different spatial scales among species with 74% of species having moderate to high population differentiation (Fst > 0.10) and 92% of species with evidence of fine-scale genetic structure. Although this suggests a high potential for trait variation, few studies associated molecular with phenotypic variation. Seventeen tree species across 11 studies revealed intraspecific variation in traits or functions. Research indicates that intraspecific variation in growth may vary two-fold and drought tolerance four-fold among genotypes highlighting the possibility to pre-adapt trees to climate change during reforestation and to use intraspecific variation to promote the use of native species in commercial forestry. Our review presents opportunities and ideas for developing seed-sourcing guidelines to take advantage of intraspecific variation in traits and function by identifying how to locate this variation, which species would benefit, and how to test for trait variation. We also highlight an emerging area of research on local adaptation, common garden studies, and adaptive drought conditioning to improve reforestation during climate change.

An ecological transcriptome approach to capture the molecular and physiological mechanisms of mass flowering in Shorea curtisii.

Climatic factors have commonly been attributed as the trigger of general flowering, a unique community-level mass flowering phenomenon involving most dipterocarp species that forms the foundation of Southeast Asian tropical rainforests. This intriguing flowering event is often succeeded by mast fruiting, which provides a temporary yet substantial burst of food resources for animals, particularly frugivores. However, the physiological mechanism that triggers general flowering, particularly in dipterocarp species, is not well understood largely due to its irregular and unpredictable occurrences in the tall and dense forests. To shed light on this mechanism, we employed ecological transcriptomic analyses on an RNA-seq dataset of a general flowering species, Shorea curtisii (Dipterocarpaceae), sequenced from leaves and buds collected at multiple vegetative and flowering phenological stages. We assembled 64,219 unigenes from the transcriptome of which 1,730 and 3,559 were differentially expressed in the leaf and the bud, respectively. Differentially expressed unigene clusters were found to be enriched with homologs of Arabidopsis thaliana genes associated with response to biotic and abiotic stresses, nutrient level, and hormonal treatments. When combined with rainfall data, our transcriptome data reveals that the trees were responding to a brief period of drought prior to the elevated expression of key floral promoters and followed by differential expression of unigenes that indicates physiological changes associated with the transition from vegetative to reproductive stages. Our study is timely for a representative general flowering dipterocarp species that occurs in forests that are under the constant threat of deforestation and climate change as it pinpoints important climate sensitive and flowering-related homologs and offers a glimpse into the cascade of gene expression before and after the onset of floral initiation.

El Niño-Southern Oscillation forcing on carbon and water cycling in a Bornean tropical rainforest

Carbon dioxide and water vapor exchanges between tropical forest canopies and the atmosphere through photosynthesis, respiration, and evapotranspiration (ET) influence carbon and water cycling at the regional and global scales. Their inter- and intra-annual variations are sensitive to seasonal rhythms and longer-timescale tropical climatic events. In the present study, we assessed the El Niño-Southern Oscillation (ENSO) influence on ET and on the net ecosystem exchange (NEE), using eddy-covariance flux observations in a Bornean rainforest over a 10-y period (2010-2019) that included several El Niño and La Niña events. From flux model inversions, we inferred ecophysiological properties, notably the canopy stomatal conductance and "big-leaf" maximum carboxylation rate (Vcmax25_BL). Mean ET values were similar between ENSO phases (El Niño, La Niña, and neutral conditions). Conversely, the mean net ecosystem productivity was highest during La Niña events and lowest during El Niño events. Combining Shapley additive explanation calculations for nine controlling factors with a machine-learning algorithm, we determined that the primary factors for ET and NEE in the La Niña and neutral phases were incoming shortwave solar radiation and Vcmax25_BL, respectively, but that canopy stomatal conductance was the most significant factor for both ET and NEE in the El Niño phase. A combined stomatal-photosynthesis model approach further indicated that Vcmax25_BL differences between ENSO phases were the most significant controlling factor for canopy photosynthesis, emphasizing the strong need to account for ENSO-induced ecophysiological factor variations in model projections of the long-term carbon balance in Southeast Asian tropical rainforests.

Characterization of Leaf Transcriptome in a Tropical Tree Species, <i>Shorea curtisii</i>, over a Flowering Season

General flowering (GF) is a synchronous flowering phenomenon in the Southeast Asian tropical rainforests that occurs at irregular intervals of multiple years. While in this study, the leaf transcriptome of a GF species, Shorea curtisii obtained from three-time points – before and after floral initiation, and post-flowering stage – was sequenced, the unpredictable intervals of GF raise conservation concerns for these under-researched forests with rich economically and ecologically important species. We assembled 243,759,478 sequencing reads into 39,943 non-redundant unigenes including 677 putative homologs of Arabidopsis thaliana flowering-related genes. Differential expression analysis conducted on pairwise comparisons of the time points identified 930 differentially expressed unigenes, which includes 17 flowering-related homologs. The differential expression of unigenes with significant enrichments of functions related to drought corroborated the involvement of drought as an environmental cue for GF, with the outcomes of this study offering an insight into the conservation of floral regulatory genes and pathways in Shorea and possibly being used as a model to better understand the floral initiation cues and regulation of GF trees.

Strategies for the discovery of potential anticancer agents from plants collected from Southeast Asian tropical rainforests as a case study.

Covering up to early 2023The present review summarizes recent accomplishments made as part of a multidisciplinary, multi-institutional anticancer drug discovery project, wherein samples comprising higher plants were collected primarily from Southeast Asia, and also from Central America, and the West Indies. In the introductory paragraphs, a short perspective is provided on the current importance of plants in the discovery of cancer therapeutic agents, and the contributions of other groups working towards this objective are mentioned. For our own investigations, following their collection, tropical plants have been subjected to solvent extraction and biological evaluation for their antitumor potential. Several examples of purified plant lead bioactive compounds were obtained and characterized, and found to exhibit diverse structures, including those of the alkaloid, cardiac glycoside, coumarin, cucurbitacin, cyclobenzofuran (rocaglate), flavonoid, lignan, and terpenoid types. In order to maximize the efficiency of work on drug discovery from tropical plant species, strategies to optimize various research components have been developed, including those for the plant collections and taxonomic identification, in accordance with the requirements of contemporary international treaties and with a focus on species conservation. A major component of this aspect of the work is the development of collaborative research agreements with representatives of the source countries of tropical rainforest plants. The phytochemical aspects have included the preparation of plant extracts for initial screening and the selection of promising extracts for activity-guided fractionation. In an attempt to facilitate this process, a TOCSY-based NMR procedure has been applied for the determination of bioactive rocaglate derivatives in samples of Aglaia species (Meliaceae) collected for the project. Preliminary in vitro and in vivo mechanistic studies carried out by the authors are described for two tropical plant-derived bioactive lead compounds, corchorusoside C and (+)-betulin, including work conducted with a zebrafish (Danio rerio) model. In the concluding remarks, a number of lessons are summarized that our group has learned as a result of working on anticancer drug discovery using tropical plants, which we hope will be of interest to future workers.

Hainan Gibbons (Nomascus hainanus), the Most Threatened and Rarest Primate in the World

Gibbons (Hylobatidae) are exclusively arboreal small apes only inhabiting in tropical rainforests of Southeast Asia [1]. Gibbons in Nomascus have 52 chromosomes and adult males and females are almost the same body size.

Evidence in stable isotope ratios for lichen‐feeding by Lithosiini moths from a tropical rainforest but not from a temperate forest

AbstractLithosiini (Lepidoptera: Erebidae: Arctiinae) is distinctive in having some species that feed on lichens, whereas the majority of moths feed on vascular plants. However, the larval diet of most Lithosiini species is poorly known. This study examines whether Lithosiini species, collected in a tropical rainforest of Borneo (nine species) and a temperate forest of Japan (eight species), feed on lichens as larvae, based on stable isotope analyses. As a result, the δ15N values for eight of nine Lithosiini species collected from Borneo were notably lower than those of nine co‐occurring herbivorous non‐Lithosiini species, and were similar to those of sympatric, lichen‐feeding termites; however, δ13C and δ15N values of one Lithosiini species (Adites sp.) were significantly higher than those of the other moth species and similar to those of humus‐feeding termites and predatory insects occurring at the same site. These results have suggested that the Lithosiini in the Southeast Asian tropical rainforests contain some species that feed on lichens as their larval main diet and at least one species whose larvae feed on humus or animal‐derived materials. In contrast, the δ13C and δ15N values of all examined Lithosiini species (eight species) in the temperate forest have suggested that their larvae fed on plants and not on lichens. Our stable isotope ratio analysis presented quantitative evidence suggesting lichen‐feeding by Lithosiini moths in a tropical rainforest without observation of feeding behavior during the larval stages.

Historical biogeography of the gingers and its implications for shifts in tropical rain forest habitats

AbstractAimThe relationships between biome shifts and global environmental changes in temperate zone habitats have been extensively explored; yet, the historical dynamics of taxa found in the tropical rain forest (TRF) remain poorly known. This study aims to reconstruct the relationships between tropical rain forest shifts and global environmental changes through the patterns of historical biogeography of a pantropical family of monocots, the Zingiberaceae.LocationGlobal.TaxonZingiberaceae.MethodsWe sampled DNA sequences (nrITS, trnK, trnL‐trnF and psbA‐trnH) from GenBank for 77% of the genera, including 30% of species, in the Zingiberaceae. Global fossil records of the Zingiberaceae were collected from literatures. Rates of speciation, extinction and diversification were estimated based on phylogenetic data and fossil records through methods implemented in BAMM. Ancestral ranges were estimated using single‐tree BioGeoBEARS and multiple‐trees BioGeoBEARS in RASP. Dispersal rate through time and dispersal rate among regions were calculated in R based on the result of ancestral estimation.ResultsThe common ancestor of the Zingiberaceae likely originated in northern Africa during the mid‐Cretaceous, with later dispersal to the Asian tropics. Indo‐Burma, rather than Malesia, was likely a provenance of the common ancestor of Alpinioideae–Zingiberoideae. Several abrupt shifts of evolutionary rates from the Palaeocene were synchronized with sudden global environmental changes.Main conclusionsIntegrating phylogenetic patterns with fossil records suggests that the Zingiberaceae dispersed to Asia through drift of the Indian Plate from Africa in the late Palaeocene. Formation of island chains, land corridors and warming temperatures facilitated the emigration of the Zingiberaceae to a broad distribution across the tropics. Moreover, dramatic fluctuations of the speciation rate of Zingiberoideae appear to have been synchronized with global climate fluctuations. In general, the evolutionary history of the Zingiberaceae broadens our understanding of the association between TRF shifts in distribution and past global environmental changes, especially the origin of TRF in Southeast Asia.

Impacts of climate change on reproductive phenology in tropical rainforests of Southeast Asia

In humid forests in Southeast Asia, many species from dozens of plant families flower gregariously and fruit synchronously at irregular multi-year intervals1–4. Little is known about how climate change will impact these community-wide mass reproductive events. Here, we perform a comprehensive analysis of reproductive phenology and its environmental drivers based on a monthly reproductive phenology record from 210 species in 41 families in Peninsular Malaysia. We find that the proportion of flowering and fruiting species decreased from 1976 to 2010. Using a phenology model, we find that 57% of species in the Dipterocarpaceae family respond to both drought and low-temperature cues for flowering. We show that low-temperature flowering cues will become less available in the future in the RCP2.6 and 8.5 scenarios, leading to decreased flowering opportunities of these species in a wide region from Thailand to the island of Borneo. Our results highlight the vulnerability of and variability in phenological responses across species in tropical ecosystems that differ from temperate and boreal biomes.

Effects of vegetation structure on avian biodiversity in a selectively logged hill dipterocarp forest

Southeast Asian tropical rainforests are shrinking at an alarming rate largely due to anthropogenic activities such as logging and agricultural expansion. The loss of tropical rainforests from human exploitations caused devastating and irreversible impacts on avian biodiversity. The establishment of protected areas is an effective tool to mitigate further forest biodiversity loss. However, the ability of degraded rainforest to support avian biodiversity is still remain little known. Here, we assessed bird assemblages in a hill dipterocarp forest in Peninsular Malaysia which was selectively logged almost three decades ago. We examined the effects of site-level attributes, particularly vegetation structure on bird community composition, species richness and abundance of selected feeding guild groups (i.e. insectivorous, carnivorous, and frugivorous). Generally, we found that a selectively logged hill dipterocarp forest can still support a large proportion of forest birds, including those species with high conservation values. Our data also revealed that avian biodiversity was positively related to the number of fallen snags, number of standing snags, number of shrubs, number of trees with DBH < 5 cm, and elevation. In contrast, avian biodiversity was negatively linked to canopy cover percentage, number of palms, and number of trees with DBH 30–50 cm. Our findings suggest the importance of post-harvest site-level attributes management in order to improve avian biodiversity in logged hill dipterocarp forests. Above all, urgent actions are needed to incorporate hill dipterocarp forests, including those already disturbed by logging into protected area networks in Peninsular Malaysia to mitigate forest biodiversity loss.

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.

Increased seed predation in the second fruiting event during an exceptionally long period of community‐level masting in Borneo

AbstractIn Southeast Asian tropical rainforests, community‐level masting (CM) occurs at irregular intervals of 2–10 years. During CM periods, many plant species from various families synchronously flower and subsequently undergo community‐level fruiting. Seed predation is a key factor in understanding the ecological and evolutionary factors affecting CM. Masting is proposed to decrease seed mortality due to predation in two ways: by depressing predator abundance through extended and unpredictable absences of seeds; and by satiating predators via mass seed production (predator satiation hypothesis). If the hypothesis is valid in these rainforests, the incidence of seed predation will be higher in a fruiting event that occurs soon after a previous fruiting event, because the intervening period of seed absence would be inadequate to starve the predators. In this study, we examined seed predation by insects, focusing on five dipterocarp species that exceptionally reproduced twice during an extended CM period. All of the five species suffered more intense seed predation in the second fruiting event, consistent with the prediction expected from the predator satiation hypothesis. Weevils, bark beetles and mammals were the main cause of increased seed predation in three, one and one plant species, respectively. However, seed predation intensity did not increase during the second fruiting event in a few combinations of predator and plant species. We discuss the possibility that competition for seeds among predators and/or the interspecific differences in life history traits among predators might affect the varying intensities of seed predation among dipterocarp species by different seed predators.

The ecology of the Asian dipterocarps

The Dipterocarpaceae is the emblematic family of South-east Asian tropical rain forests and many of the seasonally dry forests of continental South and South-east Asia. Whilst dipterocarps are pant...

Complex pollination of a tropical Asian rainforest canopy tree by flower-feeding thrips and thrips-feeding predators.

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. 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. 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. 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.

Food Habits of Asian ElephantsElephas maximusin a Rainforest of Northern Peninsular Malaysia

Little is known about the food habits of Asian elephants (Elephas maximus) in tropical rainforests of Southeast Asia. In Peninsular Malaysia, elephant habitat has been extensively modified by human intervention in the past few decades. Most of the primary forest has been logged or given way to plantations, infrastructure, and human inhabitation. Here we compare the food habits of wild elephants in three habitats of Belum-Temengor Forest Complex (BTFC): (1) primary forest, (2) selectively-logged forest, and (3) by the side of a road that bisects the forest complex. We used microhistological fecal analysis to describe elephants' diet. Elephant dung in the primary forest was mainly composed of non-grass monocotyledonous leaves (22%), woody debris (32%), and woody fiber (20%). Those in the logged forest were similar; non-grass monocotyledonous leaves accounted for 33%, woody debris for 24%, and fiber for 26%. At the roadside, elephant dung was dominated by grasses (47%). We conclude that by the road elephants shift their diet into grasses, suggesting that the road acts like a large forest gap, promoting the availability of grasses and other early succession plants. Elephant feeding by the road poses potential conservation conflicts by means of road accidents and increased contact with people.

Population Genetic Diversity in The Genus Dryoblanops Gaertn. f. (Dipterocarpaceae) Based on Nucler Microsatellite Markers

The genus Dryobalanops Gaertn. f. is a small but important genus that contains seven species and is found in the Southeast Asian tropical rain forests. Seven polymorphic nuclear microsatellite markers were analyzed in 46 natural populations of six extant Dryobalanops species (N = 700 individuals) covering the distribution range in Western Malesia. The mean gene diversity at the species level ranged from 0.392 in D. rappa to 0.635 in D. aromatica. The FST value ranged from 0.156 in D. keithii to 0.283 in D. beccarii and all FST values were highly significantly greater than zero. These results suggest that gene flow between populations has been limited and intensive genetic drift has occurred in all of the species. Plants with narrowly distributed species such as D. keithii and D. rappa, which are endemic to Borneo, tend to have lower levels of genetic diversity compared with widespread species such as D. aromatica. STRUCTURE analysis revealed that at least two of the six species could be effectively discriminated each other. The results of this study will be helpful for building effective conservation schemes as well as for providing basic data for future provenance trials of Dryobalanops species.

Biotic and abiotic drivers of dipterocarp seedling survival following mast fruiting in Malaysian Borneo

Abstract:South-East Asian tropical rain forests experience sporadic, but profuse, seed production after general flowering, leading to the synchronous emergence of various seedlings and subsequent seedling dynamics, which play a crucial role in determining species distribution and coexistence. We examined the relative importance of both biotic (initial height, conspecific seedling density) and abiotic (canopy openness, per cent sand, soil water content) drivers using survival data for 1842 seedlings of 12 dipterocarp species for 1.5 y following mast fruiting in an old-growth Bornean tropical rain forest. More than 30% of all dipterocarp seedlings survived 1.5 y after mast fruiting. When all species were analysed together, we found that initial seedling height, canopy openness and conspecific seedling density affected dipterocarp seedling survival. Negative density dependence indicated that predators were not satiated, but dipterocarp seedlings rather suffered from host-specific natural enemies or intraspecific competition. Species-level analyses of seven dipterocarp species showed large variation in response to biotic and abiotic factors. These results suggest that interspecific differences in the relative importance of biotic and abiotic effects on seedling survival might contribute to species coexistence.

Current plantation practices have negligible genetic effects on planted dipterocarps in the tropical rainforest

AbstractDipterocarp trees are ecologically and commercially important in Southeast Asian tropical rainforests. For sustainable management of forest ecosystems and conservation of biodiversity, it is essential to establish plantation methods ensuring that genetic variation of the planted trees is equivalent to that in natural forests. The genetic diversity and differentiation of Shorea leprosula and Shorea parvifolia on plantations managed by a private-sector forestry company in Indonesia and those in natural populations were compared using microsatellite markers. Genetic diversity in the planted populations was as high as that in the natural populations. No clear genetic differences between each planted population and the natural forest populations were found. The genetic variation present in planted S. leprosula and S. parvifolia populations did not appear to deteriorate in the planting system implemented in Indonesia, known as Tebang Pilih Tanam Jalur (TPTJ). These results indicate that the current plantation method practiced in the region is suitable for maintaining the original genetic composition and achieving sustainable use of tropical rainforests.

High gene flow in two thrips-pollinated South-East Asian pioneer trees: genetic diversity and population structure ofMacaranga hypoleucaandM. beccariana(Euphorbiaceae)

As a result of intensive exploitation, disturbed forests now dominate large areas of lowland tropical rainforest in South-East Asia. The genus Macaranga comprises some of the most important pioneer tree species of the region, among them M. beccariana and M. hypoleuca, two closely related obligate ant-plants pollinated by thrips. We used nuclear and plastid DNA markers to address questions of genetic diversity and population structure. Twelve plastid haplotypes were detected among 281 samples, three of which were shared between the two study species. Hybrids between the two species appear to be rare. Overall, genetic diversity in both species was moderate to high, with low levels of population differentiation, consistent with other tropical pioneer trees. Genetic structure was generally more pronounced in plastid than in nuclear data, indicating that gene flow via pollen may be more efficient than via seeds. Thrips apparently also serve as efficient pollinators over long distances, perhaps through a combination of passive dispersal by wind and active search for inflorescences in the target area. Our results indicate that M. beccariana and M. hypoleuca populations from recently disturbed habitats do not yet suffer from reduced genetic diversity or increased inbreeding.

Wide Host Ranges of Herbivorous Beetles? Insights from DNA Bar Coding

There are very few studies that have investigated host-specificity among tropical herbivorous insects. Indeed, most of the trophic interactions of herbivorous insects in Southeast Asian tropical rainforests remain unknown, and whether polyphagous feeding is common in the herbivores of this ecosystem has not been determined. The present study employed DNA bar coding to reveal the trophic associations of adult leaf-chewing chrysomelid beetles in a Bornean rainforest. Plant material ingested by the adults was retrieved from the bodies of the insects, and a portion of the chloroplast rbcL sequence was then amplified from this material. The plants were identified at the family level using an existing reference database of chloroplast DNA. Our DNA-based diet analysis of eleven chrysomelid species successfully identified their host plant families and indicated that five beetle species fed on more than two families within the angiosperms, and four species fed on several families of gymnosperms and/or ferns together with multiple angiosperm families. These findings suggest that generalist chrysomelid beetles associated with ecologically and taxonomically distant plants constitute a part of the plant-insect network of the Bornean rainforest.