Amorphophallus 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.
Animals can have both positive (e.g. via seed dispersal) and negative (e.g. via herbivory) impacts on plants. The net effects of these interactions remain difficult to predict and may be affected by overhunting and habitat disturbance, two widespread threats to tropical forests. Recent studies have documented their separate effects on plant recruitment but our understanding of how defaunation and logging interact to influence tropical tree communities is limited. From 2013 to 2016, we followed the fate of marked tree seedlings (n = 1489) from 81 genera in and outside experimental plots. Our plots differentially excluded small, medium and large-bodied mammal herbivores in logged and unlogged forest in Malaysian Borneo. We assessed the effects of experimental defaunation and logging on taxonomic diversity and plant trait (wood density, specific leaf area, fruit size) composition of seedling communities. Although seedling mortality was highest in the presence of all mammal herbivores (44%), defaunation alone did not alter taxonomic diversity nor plant trait composition. However, herbivores (across all body sizes) significantly reduced mean fruit size across the seedling community over time (95% confidence interval (CI): -0.09 to -0.01), particularly in logged forest (95% CI: -0.12 to -0.003). Our findings suggest that impacts of mammal herbivores on plant communities may be greater in forests with a history of disturbance and could subsequently affect plant functional traits and ecological processes associated with forest regeneration.
Herbivore-induced plant volatiles (HIPVs) are widely recognized as an ecologically important defensive response of plants against herbivory. Although the induction of this 'cry for help' has been well documented, only a few studies have investigated the inhibition of HIPVs by herbivores and little is known about whether herbivores have evolved mechanisms to inhibit the release of HIPVs. To examine the role of herbivore effectors in modulating HIPVs and stomatal dynamics, we conducted series of experiments combining pharmacological, surgical, genetic (CRISPR-Cas9) and chemical (GC-MS analysis) approaches. We show that the salivary enzyme, glucose oxidase (GOX), secreted by the caterpillar Helicoverpa zea on leaves, causes stomatal closure in tomato (Solanum lycopersicum) within 5 min, and in both tomato and soybean (Glycine max) for at least 48 h. GOX also inhibits the emission of several HIPVs during feeding by H. zea, including (Z)-3-hexenol, (Z)-jasmone and (Z)-3-hexenyl acetate, which are important airborne signals in plant defenses. Our findings highlight a potential adaptive strategy where an insect herbivore inhibits plant airborne defenses during feeding by exploiting the association between stomatal dynamics and HIPV emission.
Plant recovery rates after herbivory are thought to be a key factor driving recursion by herbivores to sites and plants to optimise resource-use but have not been investigated as an explanation for recursion in large herbivores. We investigated the relationship between plant recovery and recursion by elephants (Elephas maximus borneensis) in the Lower Kinabatangan Wildlife Sanctuary, Sabah. We identified 182 recently eaten food plants, from 30 species, along 14 × 50 m transects and measured their recovery growth each month over nine months or until they were re-browsed by elephants. The monthly growth in leaf and branch or shoot length for each plant was used to calculate the time required (months) for each species to recover to its pre-eaten length. Elephant returned to all but two transects with 10 eaten plants, a further 26 plants died leaving 146 plants that could be re-eaten. Recursion occurred to 58% of all plants and 12 of the 30 species. Seventy-seven percent of the re-eaten plants were grasses. Recovery times to all plants varied from two to twenty months depending on the species. Recursion to all grasses coincided with plant recovery whereas recursion to most browsed plants occurred four to twelve months before they had recovered to their previous length. The small sample size of many browsed plants that received recursion and uneven plant species distribution across transects limits our ability to generalise for most browsed species but a prominent pattern in plant-scale recursion did emerge. Plant recovery time was a good predictor of time to recursion but varied as a function of growth form (grass, ginger, palm, liana and woody) and differences between sites. Time to plant recursion coincided with plant recovery time for the elephant's preferred food, grasses, and perhaps also gingers, but not the other browsed species. Elephants are bulk feeders so it is likely that they time their returns to bulk feed on these grass species when quantities have recovered sufficiently to meet their intake requirements. The implications for habitat and elephant management are discussed.
Drought and pests are primary abiotic and biotic factors proposed as selective filters acting on species distributions along rainfall gradients in tropical forests and may contribute importantly to species distributional limits, performance, and diversity gradients. Recent research demonstrates linkages between species distributions along rainfall gradients and physiological drought tolerance; corresponding experimental examinations of the contribution of pest pressure to distributional limits and potential interactions between drought and herbivory are limited. This study aims to quantitate differential performance and herbivory as a function of species range limits across a climatic and floristic transition in Southeast Asia. Khao Chong Botanical Garden, Thailand and Pasoh Forest Reserve, Malaysia straddle the Kangar-Pattani Line. A reciprocal transplantation across a seasonality gradient was established using two groups of species ("widespread" taxa whose distributions include seasonally dry forests and "aseasonal" taxa whose distributions are limited to aseasonal forests). Growth, biomass allocation, survival, and herbivory were monitored for 19 months. Systematic differences in performance were a function of species distribution in relation to rainfall seasonality. In aseasonal Pasoh, aseasonal species had both greater growth and survivorship than widespread species. These differences were not a function of differential herbivory as widespread and aseasonal species experienced similar damage in the aseasonal forest. In seasonally dry Khao Chong, widespread species showed higher survivorship than aseasonal species, but these differences were only apparent during drought. We link this differential performance to physiological mechanisms as well as differential tolerance of biotic pressure during drought stress. Systematic decreases in seedling survival in aseasonal taxa during drought corresponded with previously documented physiological differences and may be exacerbated by herbivore damage. These results have important implications for tropical diversity and community composition in light of predicted increases in the frequency and severity of drought in hyperdiverse tropical forests.
Naturally, plant habitats are exposed to several potential effects of biotic and different abiotic environmental challenges. Several types of micro-organisms namely; bacteria, viruses, fungi, nematodes, mites, insects, mammals and other herbivorous animals are found in large amounts in all ecosystems, which lead to considerable reduction in crop productivity. These organisms are agents carrying different diseases that can damage the plants through the secretion of toxic-microbial poisons that can penetrate in the plant tissues. Toxins are injurious substances that act on plant protoplast to influence disease development. In response to the stress effect, plants defend themselves by bearing some substances such as phytoalexins. Production of phytoalexins is one of the complex mechanisms through which plants exhibit disease resistance. Several findings specifically on phytoalexins have widen the understanding in the fields of plant biochemistry and molecular biology. However, this review reports the interaction of toxins and phytoalexins in plant-pathogen cycle, research progress on the association of phytoalexins with plant disease resistance as well as the role of the phytoalexins in plant disease control.
Rehabilitation of degraded forest is being intensified in Borneo, effort by the INIKEA Rehabilitation Project in Luasong (Sabah) has resulted in healthy growth of native timber species to Borneo. Slow growth rate of Dipterocarps has been attributed to presence of biofoulers on its leaves and herbivory. Therefore, an investigation was conducted to document the coverage and distribution of foliicolous lichens on the leaves of five common timber species Dipterocarpus conformis, Dryobalanops lanceolate, Dryobalanops keithii, Shorea ovalis, and Shorea fallax, planted during this project in 2008. Colonization of foliicolous lichen on timber species was seen to exist in two distinct pattern; leaves of genus Shorea showed surface colonization of 28-29%, while genus Dipterocarpus and Drybalanopsis exhibited a lesser coverage of 15-18%. A total of 32 species belonging to nine families were recorded during the course of this study. Lichen diversity was higher on leaves of Dipterocarpus conformis and Shorea ovalis as compared to the other three species. In addition, nine new records of foliicolous lichens were isolated, identified and their descriptions are presented here.
Taste perception is an essential function that provides valuable dietary and sensory information, which is crucial for the survival of animals. Studies into the evolution of the sweet taste receptor gene (TAS1R2) are scarce, especially for Bornean endemic primates such as Nasalis larvatus (proboscis monkey), Pongo pygmaeus (Bornean orangutan), and Hylobates muelleri (Muller's Bornean gibbon). Primates are the perfect taxa to study as they are diverse dietary feeders, comprising specialist folivores, frugivores, gummivores, herbivores, and omnivores. We constructed phylogenetic trees of the TAS1R2 gene for 20 species of anthropoid primates using four different methods (neighbor-joining, maximum parsimony, maximum-likelihood, and Bayesian) and also established the time divergence of the phylogeny. The phylogeny successfully separated the primates into their taxonomic groups as well as by their dietary preferences. Of note, the reviewed time of divergence estimation for the primate speciation pattern in this study was more recent than the previously published estimates. It is believed that this difference may be due to environmental changes, such as food scarcity and climate change, during the late Miocene epoch, which forced primates to change their dietary preferences. These findings provide a starting point for further investigation.
Riparian areas hold vast number of flora and fauna with exceptional contributions to the ecosystem. A study was conducted in Sungai Sepetang, Sungai Rembau and Sungai Chukai to identify the insect community in a riparian zone of Peninsular Malaysia. Sampling was conducted in six consecutive months from December 2017 to May 2018 during both day and night using sweep nets. Twenty sampling stations (S1-S20) had been assembled along the riverbanks with an average distance of 200 m between each station. The 17,530 collected insects were from 11 orders and consisted of Diptera, Coleoptera, Hemiptera, Hymenoptera, Lepidoptera, Neuroptera, Orthoptera, Blattodea, Thysanoptera, Mantodea and Odonata. The three most abundant orders were Diptera (33.84%; 5933 individuals), Coleoptera (28.82%; 5053 individuals) and Hemiptera (25.62%: 4491 individuals). The collected insect community consisted of different guilds such as the scavenger, predator, herbivore, pollinator and parasitoid. Sungai Sepetang and Sungai Rembau were dominated by mangrove flora, Sonneratia caseolaris (Myrtales: Lythraceae), while Sungai Chukai was dominated by Barringtonia racemosa. There was a significant difference (p < 0.05) in the composition of insects between the three rivers though clustering analysis showed that the insect communities in Sungai Sepetang and Sungai Rembau were 100% similar compared to Sungai Chukai which consisted of a totally different community. There is a significant negative correlation between abundance of insects with salinity and wind speed at Sungai Chukai and Sungai Sepetang.
Much of the forest remaining in South East Asia has been selectively logged. The processes promoting species coexistence may be the key to the recovery and maintenance of diversity in these forests. One such process is the Janzen-Connell mechanism, where specialized natural enemies such as seed predators maintain diversity by inhibiting regeneration near conspecifics. In Neotropical forests, anthropogenic disturbance can disrupt the Janzen-Connell mechanism, but similar data are unavailable for South East Asia. We investigated the effects of conspecific density (two spatial scales) and distance from fruiting trees on seed and seedling survival of the canopy tree Parashorea malaanonan in unlogged and logged forests in Sabah, Malaysia. The production of mature seeds was higher in unlogged forest, perhaps because high adult densities facilitate pollination or satiate pre-dispersal predators. In both forest types, post-dispersal survival was reduced by small-scale (1 m(2)) conspecific density, but not by proximity to the nearest fruiting tree. Large-scale conspecific density (seeds per fruiting tree) reduced predation, probably by satiating predators. Higher seed production in unlogged forest, in combination with slightly higher survival, meant that recruitment was almost entirely limited to unlogged forest. Thus, while logging might not affect the Janzen-Connell mechanism at this site, it may influence the recruitment of particular species.
Elucidating how dispersal and landscape connectivity influence metacommunity stability will shed light on natural processes structuring ecosystems and help prioritize conservation actions in an increasingly fragmented world. Much of the theoretical and mathematical development of the metacommunity concept has been based on simplified experimental systems or simulated data. We still have limited understanding of how variation in the habitat matrix and species-specific differences in dispersal ability contribute to metacommunity dynamics in heterogeneous landscapes. We model a metacommunity of rainforest mammals in Borneo, a tropical biodiversity hotspot, where protected areas are increasingly isolated by ongoing habitat disturbance and loss. We employ a combination of hierarchical models of local abundance, circuit-theory-based dispersal analysis, and metapopulation models. Our goal was to understand which landscape links were the most important to metapopulation persistence and metacommunity stability. Links were particularly important if they were short and connected two large patches. This was partly because only the very shortest links could be traversed by poorly dispersing species, including small herbivores such as chevrotains (Tragulus spp.) and porcupines. Links that join large patches into a "super-patch" may also promote island-mainland rather than Levins-type metapopulation dynamics for good dispersers, particularly large carnivores such as clouded leopards (Neofelis diardi) and sun bears (Helarctos malayanus), reducing metapopulation extinction risk and thereby enhancing metacommunity stability. Link importance to metacommunity stability was highly correlated between heterogeneous and homogeneous landscapes. But link importance to metapopulation capacity varied strongly across species, and the correlation between heterogeneous and homogeneous landscape matrix scenarios was low for poorly dispersing taxa. This suggests that the environmental conditions in the area between habitat patches, the landscape matrix, is important for assessing certain individual species but less so for understanding the stability of the entire metacommunity.
Ecosystem functioning is dependent a lot on large mammals, which are, however, vulnerable and facing extinction risks due to human impacts mainly. Megafauna of Asia has been declining for a long, not only in numbers but also in their distribution ranges. In the current study, we collected information on past and current occurrence and distribution records of Asia's megafauna species. We reconstructed the historical distribution ranges of the six herbivores and four carnivores for comparison with their present ranges, to quantify spatially explicit levels of mega-defaunation. Results revealed that historically the selected megafauna species were more widely distributed than at current. Severe range contraction was observed for the Asiatic lion, three rhino species, Asian elephant, tigers, and tapirs. Defaunation maps generated have revealed the vanishing of megafauna from parts of the East, Southeast, and Southwest Asia, even some protected Areas losing up to eight out of ten megafaunal species. These defaunation maps can help develop future conservation policies, to save the remaining distribution ranges of large mammals.
Species of the benthic dinoflagellate Gambierdiscus produce polyether neurotoxins that caused ciguatera fish/shellfish poisoning in human. The toxins enter marine food webs by foraging of herbivores on the biotic substrates like macroalgae that host the toxic dinoflagellates. Interaction of Gambierdiscus and their macroalgal substrate hosts is believed to shape the tendency of substrate preferences and habitat specialization. This was supported by studies that manifested epiphytic preferences and behaviors in Gambierdiscus species toward different macroalgal hosts. To further examine the supposition, a laboratory-based experimental study was conducted to examine the growth, epiphytic behaviors and host preferences of three Gambierdiscus species towards four macroalgal hosts over a culture period of 40 days. The dinoflagellates Gambierdiscus balechii, G. caribaeus, and a new ribotype, herein designated as Gambierdiscus type 7 were initially identified based on the thecal morphology and molecular characterization. Our results showed that Gambierdiscus species tested in this study exhibited higher growth rates in the presence of macroalgal hosts. Growth responses and attachment behaviors, however, differed among different species and strains of Gambierdiscus over different macroalgal substrate hosts. Cells of Gambierdiscus mostly attached to substrate hosts at the beginning of the experiments but detached at the later time. Localized Gambierdiscus-host interactions, as demonstrated in this study, could help to better inform efforts of sampling and monitoring of this benthic toxic dinoflagellate.
Plants have evolved numerous constitutive and inducible defence mechanisms to cope with biotic and abiotic stresses. These stresses induce the expression of various genes to activate defence-related pathways that result in the release of defence chemicals. One of these defence mechanisms is the oxylipin pathway, which produces jasmonates, divinylethers and green leaf volatiles (GLVs) through the peroxidation of polyunsaturated fatty acids (PUFAs). GLVs have recently emerged as key players in plant defence, plant-plant interactions and plant-insect interactions. Some GLVs inhibit the growth and propagation of plant pathogens, including bacteria, viruses and fungi. In certain cases, GLVs released from plants under herbivore attack can serve as aerial messengers to neighbouring plants and to attract parasitic or parasitoid enemies of the herbivores. The plants that perceive these volatile signals are primed and can then adapt in preparation for the upcoming challenges. Due to their 'green note' odour, GLVs impart aromas and flavours to many natural foods, such as vegetables and fruits, and therefore, they can be exploited in industrial biotechnology. The aim of this study was to review the progress and recent developments in research on the oxylipin pathway, with a specific focus on the biosynthesis and biological functions of GLVs and their applications in industrial biotechnology.
Overhunting reduces important plant-animal interactions such as vertebrate seed dispersal and seed predation, thereby altering plant regeneration and even above-ground biomass. It remains unclear, however, if non-hunted species can compensate for lost vertebrates in defaunated ecosystems. We use a nested exclusion experiment to isolate the effects of different seed enemies in a Bornean rainforest. In four of five tree species, vertebrates kill many seeds (13-66%). Nonetheless, when large mammals are excluded, seed mortality from insects and fungi fully compensates for the lost vertebrate predation, such that defaunation has no effect on seedling establishment. The switch from seed predation by generalist vertebrates to specialist insects and fungi in defaunated systems may alter Janzen-Connell effects and density-dependence in plants. Previous work using simulation models to explore how lost seed dispersal will affect tree species composition and carbon storage may require reevaluation in the context of functional redundancy within complex species interactions networks.
1. Study of the structure and mode of life of Malleus regula provides the basis for consideration of the "hammer" species, M. malleus and M. albus.
2. M. regula occurs byssally attached, vertically disposed on rocky substrates associated with mud and is widely distributed in the tropical Indo-Pacific.
3. The distal two-thirds of the elongated shell is exclusively prismatic. By means of special pallial retractors the mantle lobes can be withdrawn within the nacreous region.
4. The massive opisthodetic ligament has a short secondary extension of fusion layer.
5. A promyal chamber on the right side proximal to the adductor increases water flow into the exhalant chamber.
6. The long filibranch ctenidia provide a vertically extended food-collecting surface.
7. The foot is concerned with planting of the massive byssus which emerges through a notch in the right valve but on the under ( i.e., dorsal) surface. There is also a unique and very long accessory foot, ventrally grooved, everywhere ciliated and in constant writhing activity due to blood pressure and intrinsic muscle. Moving freely throughout the lower mantle cavity it can only be concerned with cleansing.
8. Pseudofaeces are ejected from the distal tip of the mantle cavity.
9. M. malleus, the black hammer shell, occurs vertically embedded in coarse sand or sandy gravel. Byssus threads are attached to fragments within the substrate. The great anterior and posterior elongations of the hinge line (also exclusively prismatic) are separated by the byssal notch (now affecting both valves).
10. Shells are usually excessively irregular due to the great exposure to damage and the almost unlimited powers of rapid repair by the three pallial extensions.
11. M. albus, the white hammer shell, is stouter and inhabits muddy sand. During growth it loses the byssus with reduction of the foot and byssal retractors and closure of the byssal notch. The accessory foot is not affected. The animal becomes anchored in the substrate exclusively by the anterior and posterior extensions of the shell.
12. Description of the typically rounded Isognomon ephippium leads to that of the elongated I. isognomon which occupies precisely the same habitat as M. regula.
13. It lacks the pallial retractors, promyal chamber and accessory foot of Malleus, the nacreous region is more extended distally and the ligament is multivincular (the formation of which is discussed), producing some posterior, but never any anterior, extension of the hinge line.
14. A remarkably dense mixed bed of M. regula and I. isognomon in Darvel Bay, Sabah (Borneo), is described. Different spawning periods, by preventing competition during settlement, may account for this complete intermixing of sympatric species, which, however, are generalized herbivores where numbers are not limited by food supply.
15. From a basic epifaunal habit (Pteria, Isognomon, M. regula), members of the Pteriacea have become adapted for infaunal life within sponges (Vulsella, Crenatula) or within soft substrates ( M. malleus, M. alba and the Pinnidae).
16. There is final discussion about elongation in monomyarians, i.e., in the genus Malleus and in I. isognomon.
Contamination of insect DNA for RAPD-PCR analysis can be a problem because many primers are non-specific and DNA from parasites or gut contents may be simultaneously extracted along with that of the insect. We measured the quantity of food ingested and assimilated by two sympatric populations of brown planthopper (BPH), Nilaparvata lugens, one from rice and the other from Leersia hexandra (Poaceae), a wetland forage grass, and we also investigated whether host plant DNA contaminates that of herbivore insects in extractions of whole insects. Ingestion and assimilation of food were reduced significantly when individuals derived from one host plant were caged on the other species. The bands, OPA3 (1.25), OPD3 (1.10), OPD3 (0.80), OPD3 (0.60), pUC/M13F (0.35), pUC/M13F (0.20), BOXAIR (0.50), peh#3 (0.50), and peh#3 (0.17) were found in both rice-infesting populations of brown planthopper and its host plant (rice). Similarly, the bands, OPA4 (1.00), OPB10 (0.70), OPD3 (0.90), OPD3 (0.80), OPD3 (0.60), pUC/ M13F (0.35), pUC/M13F (0.20), and BOXAIR (0.50) were found in both Leersia-infesting populations of brown planthopper and the host plant. So, it is clear that the DNA bands amplified in the host plants were also found in the extracts from the insects feeding on them.
Reducing the size of food particles is crucial for herbivores. Seasonal dietary changes are known to influence animals' chewing efficiency. Proboscis monkeys (Nasalis larvatus) are foregut fermenters, with a high chewing efficiency allowing them to achieve very fine faecal particles. In this study, we investigated how proboscis monkeys' chewing efficiency varies between wet and dry seasons, hypothesising differences possibly related to diet change. Faecal particle size analysis is an established approach to estimate chewing efficiency in mammalian herbivores. We analysed 113 proboscis monkey faecal samples collected in the Lower Kinabatangan Wildlife Sanctuary, between 2015 and 2017. By following standard sieve analysis protocols, we measured a mean particle size MPS0.025-8 of 0.45 ± 0.14 mm, and confirmed a previous result that proboscis monkeys have a very low faecal MPS. This study highlights a seasonal influence on proboscis monkeys' chewing efficiency, with smaller MPS (better chewing efficiency) during the wet season. During that time of the year, individuals may potentially change their diet, as all faecal samples contained intact seeds. Whether the seasonal MPS difference in proboscis monkeys is smaller than in other colobines due to their "rumination" strategy remains to be investigated.
Free-living animals must make dietary choices in terms of chemical and physical properties, depending on their digestive physiology and availability of food resources. Here we comprehensively evaluated the dietary choices of proboscis monkeys (Nasalis larvatus) consuming young leaves. We analysed the data for leaf toughness and digestibility measured by an in vitro gas production method, in addition to previously reported data on nutrient composition. Leaf toughness, in general, negatively correlated with the crude protein content, one of the most important nutritional factors affecting food selection by leaf-eating primates. This result suggests that leaf toughness assessed by oral sensation might be a proximate cue for its protein content. We confirmed the importance of the leaf chemical properties in terms of preference shown by N. larvatus; leaves with high protein content and low neutral detergent fibre levels were preferred to those of the common plant species. We also found that these preferred leaves were less tough and more digestible than the alternatives. Our in vitro results also suggested that N. larvatus were little affected by secondary plant compounds. However, the spatial distribution pattern of plant species was the strongest factor explaining the selection of the preferred leaf species.
Fruit phenotypes are often hypothesised to be affected by selection by frugivores. Here, we tested two hypotheses concerning frugivore-fruit interactions from the perspective of fruit colours. We measured the spectral properties of 26 fruits and the associated leaves of plants from 2 islands in New Zealand. Visual observations were also performed to record the birds that fed on the fruits. First, we tested the fruit-foliage hypothesis, where fruit colours are assumed to be evolutionarily constrained by their own leaf colour to maximise colour contrast and fruit conspicuousness. We ran a null model analysis comparing fruit colour contrast using an avian eye model. Second, we tested the frugivore specificity hypothesis, where specific fruit colours are thought to be connected with a specific bird frugivore. We performed a regression on the number of bird visits against the fruit colour in tetrahedral colour space based on an avian eye calculation using Mantel's test. The results show that fruit colours are not constrained by their own leaf colours. There is also no relationship or pattern suggesting a link between a specific fruit colour and specific bird visitors. We suggest that although fruit colour is one of the most highly discussed components, it is not the most important single deciding factor in frugivore fruit selection.