Weed Lantana Camara Research Articles

High Impacts of Invasive Weed Lantana camara on Plant Community and Soil Physico-Chemical Properties across Habitat Types in Central Nepal

Although the effects of invasive alien plants on natural ecosystems are well known, the effects of specific plant species can vary across habitat types and disturbance intensity. This study was carried out to analyze the effects of Lantana camara on associated vegetation and soil physico-chemical properties at invaded and non-invaded sites across three different habitat types (forest edge, fallow land, and roadside) in central Nepal. We sampled 50 pairs of 5 m × 5 m (for shrub species) and 1 m × 1 m (for herbs species) plots at invaded and non-invaded sites in each habitat and recorded community variables for each species within the sampling plots for both wet (monsoon) and dry (pre-monsoon) seasons. Further, we collected soil samples from each quadrat and determined the soil physico-chemical properties. We recorded 137 species of flowering plants (119 from non-invaded and 97 from invaded plots) and classified them in accordance with life form/habit. In invaded sites, we found a significant decline in species diversity as indicated by the Simpson and Shannon diversity indices. Specifically, L. camara reduced the species richness, Simpson index, and Shannon diversity index by 36.84%, 11.84%, and 40.21%, respectively. Soil nutrients such as total nitrogen, soil organic carbon, and available phosphorus were significantly higher in invaded sites than non-invaded ones except for available potassium and soil pH. This study provided evidence that Lantana L. camara has a substantial impact on the understory plant community assemblage and the physico-chemical properties of soil. The results suggest that the protection of native plant community requires management of L. camara by implementing appropriate measures.

Computational design and in vitro assay of lantadene-based novel inhibitors of NS3 protease of dengue virus

Abstract Dengue virus (DENV) infection is one of the diseases for which no drug is available for the treatment. The DENV NS2B-NS3 protease is considered to be the prime target for anti-dengue drug development because of its importance in the development of new virus subunits via DENV poly-protein breakdown. Pentacyclic triterpenoids (Lantadenes) from the weed Lantana camara L. and its semi-synthetic congeners have shown a wide array of biological activities in the last two decades. The virtual screening strategy was used on the library of 78 natural and semi-synthetic lantadenes to predict the potent antagonists for the NS2B-NS3 protease enzyme of DENV and their experimental validation by in vitro assay of lead molecules. In the in silico analysis of 78 triterpenoids, two lead molecules (−10.60 and −9.93 kcal/mol) were predicted to be inhibitors of protease (viral) when compared to its reference ligand 1,8-dihydroxy-4,5-dinitroanthraquinone (−5.377 kcal/mol). At the same time, binding affinity, pharmacokinetic, and toxicity profiling, along with molecular dynamics simulations, were studied. The in vitro viral infection inhibition assay inferred that lead molecule 62 exhibited a 60% and 45% reduction in DENV titers at 10 and 5 µM concentrations, respectively. The lead molecule 62 can further be optimized for its pharmacophore and has the potential to be developed as a drug-like molecule.

Effects of the Density of Invasive Lantana camara Plants on the Biodiversity of Large and Small Mammals in the Groenkloof Nature Reserve (GNR) in South Africa

Multi-scale approaches have been used to determine scales at which mammal species are responding to habitat destruction due to invasion, but the impacts of weeds on mammals have not been extensively studied, especially in Africa. Inside the Groenkloof Nature Reserve (GNR), we assessed how mammals are affected by an invasive weed Lantana camara. A series of models were applied to determine the differences in species abundance as well as richness, separated for large and small mammals. When diversity indices were used, an Analysis of Variance (ANOVA) revealed no statistically significant difference between treatments (F5 = 0.233, p = 0.945) for large mammals. The results of a Generalised Linear Mixed Model (GLMM) showed that vegetation type (Wald χ22 = 120.156; p < 0.01) and foraging guilds (Wald χ23 = 76.771; p < 0.01) were significant predictors of large mammal species richness. However, for small mammals, the results of a GLMM showed that only treatment type (Wald χ25 = 10.62; p = 0.050) was a significant predictor of the number of small mammals trapped. In addition, the ANOVA revealed statistically significant differences in species diversity between treatments (F5 = 0.934; p < 0.001) and by season (F1 = 9.122 p = 0.003) for small mammals. The presence of L. camara coupled with other predictors was associated with differences in large mammal abundances and diversity, and differences in how these large mammals were distributed across the landscape. Furthermore, the highest species diversity was found in the spring for small mammals. Therefore, for all the mammals studied, the presence of L. camara negatively affected species abundance, richness, and diversity, as well as how these species were distributed across the invaded and cleared areas.

EFFICACY OF DIFFERENT TREATMENTS AGAINST POTATO TUBER MOTH (PHTHORIMAEA OPERCULELLA ZELLER) IN ORDINARY STORAGE CONDITION

Potato tuber moth, (Phthorimaea operculella Zeller) is one of the most destructive pests of potato damaging the potato tuber in the storage condition leading to huge loss of potato tubers. An experiment was conducted to assess the effects of different treatments for the management of potato tuber moths in storage conditions in Kavre, Nepal. The experiment was conducted in a Completely Randomized Design (CRD) with seven different treatments and three replications. The treatments were T1 (control), T2 (Artemesia vulgaris), T3 (Lantana camara), T4 (Mentha arvensis), T5 (Eucalyptus), T6 (Malathion), and T7 (Emamectin benzoate). Tuber treated with Malathion before storage showed least infection percentage and severity caused by PTM. In botanicals, Lantana camara seemed more effective than Mentha arvensis, Eucalyptus, and Artemesia vulgaris. Tuber rot caused by PTM was found to be least in tubers treated with Malathion, Emamectin benzoate, and Lantana camara in storage. Analyzing all the parameters, eco-friendly management of PTM can be done by using the weed Lantana camara. Chemical pesticides are to be used only on seed tubers that need to be stored for a really long time. Seed tubers treated with various botanicals may also protect tubers from PTM infestation during storage, albeit for a shorter period of time. The most potent plant found was Lantana camara.

Weed biomass: Bioconversion through composting followed by vermicomposting to optimize time required

The potential of biodegradable wastes as resources is explored widely. Biomass conversion into organic fertilizers is substitute to chemical fertilizers for environmental benefits. Vermicompost is one of the quality rich organic fertilizers produced by bioconversion technology with the help of earthworm. The unwanted plants disturbing ecosystem termed as weeds is a major issue for management. The current study focused on the terrestrial weed Lantana camara biomass management through rotary drum in-vessel pre-composting combined with vermicomposting. Vermicomposting (V) and Rotary Followed by Vermicomposting (RFV), both these techniques were performed individually for the stabilization Lantana camara biomass. The Total Organic Carbon (TOC) was 27.88 % and 24.03 % at the end of V and RFV. Total Kjeldahl Nitrogen (TKN), Total Phosphorus (TP) obtained were 2.93 %, 11.03/kg respectively from RFV was higher than V alone. The final C/N ratio was <20. The reduced time for RFV as compared to V was observed.

Exploration of anticancer potential of Lantadenes from weed Lantana camara: Synthesis, in silico, in vitro and in vivo studies

Naturally occurring pentacyclic triterpenoids and their semisynthetic analogues have engrossed increasing attention for their anticancer potential and exhibiting promising role in discovery of new anticancer agents. Present study include the semi synthetic modifications of Lantadenes from the weed Lantana carama and their structures delineation by FT-IR, 1H-NMR, 13C-NMR & mass spectroscopy. All the compounds were scrutinized for in vitro cytotoxicity, ligand receptor interaction and in vivo anticancer studies. Most of the novel analogues displayed potent antiproliferative activity against A375 & A431 cancer cell lines and found superior to parent Lantadenes. In particular, 3β-(4-Methoxybenzoyloxy)-22β-senecioyloxy-olean-12-en-28-oic acid was found to be most suitable compound, with IC50 value of 3.027 μM aganist A375 cell line having least docking score (−69.40 kcal/mol). Promising anticancer potential of the lead was further indicated by significant reduction in tumor volume and burden in two stage carcinoma model. These findings suggests that the Lantadene derivatives may hold promising potential for the intervention of skin cancers.

Effects of Toxic Weed Lantana camara on the Feeding Behaviour and Insecticidal Activity of Spodoptera litura Fab. (Lepidoptera:Noctuidae)

: The aim of the present investigation was to determine the potential effects of toxic weed Lantana camara on the feeding behaviour of Spodoptera litura (Fabricius) on the basis of Preference index and insecticidal activity using Residual toxicity test - Leaf residue film method (LRFM). Screening process is an important aspect in order to understand the potential activity of the crude extract against any pest, as it depends on various factors such as dose, species-specific behaviour, age of the larvae, solvent type etc. This study was carried out using methanolic extract of Lantana camara at three different concentrations (1%, 3% and 5%) against third instar larvae of the pest. Results showed significant phagostimulant feeding activity at all three concentrations with C-value (1.5, 1.34 and 1.35, respectively) over control. Insecticidal activity was found as 73.33% at 1% concentration, 60% at 3% concentration and 100% at 5% concentration. From this screening investigation, we concluded that methanolic extract Lantana camara exhibit significant phagostimulant activity at these concentrations. It could also be concluded that Lantana camara do not have antifeedant activity at all three concentrations but might have induced significant toxicity/poison after ingestion of food.

Assessment of the microcyclic rust Puccinia lantanae as a classical biological control agent of the pantropical weed Lantana camara

Lantana camara is a flowering shrub of the family Verbenaceae, native to the Americas which has become a major invasive weed in the Palaeotropics; affecting both natural and agricultural ecosystems. It has been the focus of classical biological control for over a century but has proven to be a problematic target because of its high genetic diversity. Here, we report on an aggressive pathotype of the microcyclic rust Puccinia lantanae collected in the Amazonian rainforest, which – based on greenhouse screening – is damaging to a wide range of biotypes of the L. camara complex. Host-range testing within the Verbenaceae and related plant families, involving leaf clearing and staining, showed the pathotype to be highly specific to L. camara sensu lato but with detectable symptoms in several other verbenaceous species. These results, together with a taxonomic re-appraisal of Puccinia lantanae, are discussed in relation to the potential of the rust as a classical biological control agent of L. camara. We conclude that this pathotype of P. lantanae is a valuable addition to the biological control armoury and posit that it should be especially successful in humid forest situations.

Bioinspired Metal-Free Fluorescent Carbon Nanozyme with Dual Catalytic Activity to Confront Cellular Oxidative Damage

Development of metal-free, recyclable enzyme mimics is challenging and requires key chemical modifications at the molecular level. Here, nitrilotriacetic acid-functionalized carbon nanospheres (LC-CNS@NTA) were prepared from the nitrogen-rich weed Lantana camara (LC) using a simple hydrothermal reaction condition. Transmission electron microscopy (TEM) studies revealed size of ∼160 ± 20 nm for LC-CNS@NTA whereas, the same showed fluorescence emission at ∼520 nm with a ∼63% quantum yield. Furthermore, LC-CNS@NTA showed strong peroxidase (Pxrd) activity toward a wide range of substrate viz., H2O2, 3,3',5,5'-tetramethylbenzidine, and o-phenylenediamine with Km and Vmax values of ∼257 μM and 1.06 μM/s, 282 μM and 1.47 μM/s, and 270.8 μM and 1.647 μM/s, respectively. Interestingly, this also showed catalase (CAT) activity against H2O2 with Km and Vmax values of ∼0.374 μM and 1.87 μM/s, respectively. It was observed that LC-CNS@NTA could effectively reduce the oxidative stress-induced cytotoxicity of HEK293 cells via retention of mitochondrial membrane potential, prevention of lipid peroxidation and DNA damage. It was further found that LC-CNS@NTA-treated cells showed reduced level of intracellular protein carbonylation and protein aggregation. The finding of the present study is expected to pave the path for designing engineered metal-free carbon nanozyme with dual enzyme mimic activity.

A strategy to decrease vectorial competence of dengue mosquito Aedes aegypti by alteration of its gut microbiota using Indian traditional medicinal plants

In the present study, the sensitivity of the gut microbes of dengue fever mosquito Aedes aegypti to Indian traditional medicinal plants was evaluated. The microbes were isolated from the midgut of laboratory-reared fourth instar larvae of Ae. aegypti and grown on Luria-Bertini agar plates at an optimum temperature of 27oC. The microbial colonies were differentiated based on their characteristics such as size, shape, opacity, elevation, consistency, and rate of growth. The axenic culture of different strains was obtained by streaking method. Ten different types of microbial clones were identified up to species level using Biolog’s advanced phenotypic technology. Five Indian traditional plants: Ocimum sanctum, Azadirachta indica, Catharanthus roseus, Curcuma longa, and Syzygium aromaticum and an invasive obnoxious weed Lantana camara were used in the present study. The extracts of the specific parts of individual plants were prepared in ethanol and hexane using ‘Soxhlet apparatus’. The extracts were screened for their antimicrobial activities by disc diffusion assay. The results indicate that the plants used in the present study possessed antimicrobial activities against gut microbes of Ae. aegypti. However, the sensitivity of different microbes to the extracts varied. The zone of inhibition observed after 24 h of incubation revealed that ethanol extract of A. indica has the most potent antibacterial activity; followed by that of S. aromaticum, C. longa and O. sanctum. L. camara and C. roseus were least effective against gut microbes of Ae. aegypti.

Production of compost with biopesticide property from toxic weed Lantana: Quantification of alkaloids in compost and bacterial pathogen suppression

Toxic weed Lantana camara foliage was composted with cow dung in 2:1 and 1:1 ratio (v/v) and changes in physicochemical characteristics, and faecal coliform bacterial population (Escherichia coli and Salmonella) was estimated for 35 d. Results showed a significant increase in total N (1.48-1.69-folds), Paval (6.87–9.19-folds), and total K (1.08−1.23-folds) content, while a decrease in C/N ratio (1.87–2.13-folds) and total organic carbon (1.12−1.46-folds) after composting process. Germination index (GI) results (> 70 %) suggested the non-toxic property of Lantana compost against tested rapeseed mustard seeds. E. coli and Salmonella population reduced to the safe limit after 35 d composting. Compost extract (sterilized and non-sterilized) (from 2:1 setup) showed about 0.88 – 1.08-, 0.88 – 0.96-, 0.83 – 0.94-, and 0.79–1.08-folds higher inhibition in Xanthomonas citrus, Xanthomonas campestris, Erwinia carotovora, and Pseudomonas aerogenosa, respectively, indicating strong pathogen-inhibiting substances in Lantanacompost. GC–MS analysis of compost extract indicated the presence of isomers of several compounds of biocidal property – hexadecane (9-hexyl and 9-octyl); 2-tridecyl ester; eicosane; tetradecane, heptacosane (1-chloro- and 9-hexyl); heptadecane, octadecane, 3-ethyl-5-(2-ethylbutyl)-, heptacosane, tetradecane, 2,6,10-trimethyl-, etc.). Result revealed that Lantana compost could be used as biomanure with biopesticide properties for sustainable organic farming system.

Deriving double dividends through linking payments for ecosystem services to environmental entrepreneurship: The case of the invasive weed Lantana camara

A payment for ecosystem services mechanism is designed to support an environmental enterprise aimed at controlling Lantana camara, an invasive weed that is costly to eradicate. A forest reserve manager engages the local community in lantana control efforts. The community converts the weeds into household durable items for sale. However, as markets for such products may not account for the environmental services generated through weed control, the enterprise could fail for want of additional financial support. The challenge addressed in this paper is to incorporate the full environmental benefits of the weed-based enterprise and provide adequate compensation to the local community. An optimal compensation mechanism is derived through linking the ecological dimension of weed growth to its impact on biodiversity values within the reserve. Results indicate that optimal payments to the community would need to take into consideration both the value addition to the environment from controlling the invasive weed and the opportunity cost of participation by the community. When there exists a risk of enterprise failure due to low profitability, higher payments by the manager are required. However, the best environmental outcomes are obtained when the manager incorporates the welfare of the local community within the utility function.

Adsorptive removal of toxic dyes from aqueous phase using notorious weed Lantana camara (Linn.) as biosorbent

The potential of Lantana camara L. in raw (LR) and modified form (LM) for adsorptive removal of two basic dyes, namely Rhodamine B (RB) and methylene blue (MB), from aqueous solution has been investigated. The adsorbent was characterized by various analytical techniques. The results obtained indicate that adsorption of the dyes strongly depends on pH, initial dye concentration, contact time, and presence of surfactant in batch mode and on flow rate and bed depth in column mode. Kinetic studies revealed that removal of the dyes was governed by pseudo-second-order kinetics and a film diffusion mechanism controls the overall rate of the sorption process. The equilibrium adsorption data were interpreted using various isotherm models, and the data were best fit by the Freundlich isotherm model. Modified adsorbent displayed improved adsorption capacity for RB and MB of 34.24–147.05 mg/g and 23.25–111.12 mg/g, respectively, at 30 °C. Thermodynamic parameters indicated that the dye removal process was spontaneous, endothermic, and chemical in nature. The highest desorption efficiency of spent adsorbent was achieved using sulfuric acid (1 M). The results show that LM has considerable potential for removal of RB and MB from aqueous solution.

Negative effect of litter of invasive weed Lantana camara on structure and composition of vegetation in the lower Siwalik Hills, northern India

Lantana camara, an aromatic shrub, native to tropical America, was introduced into India for ornamental hedging, but later escaped and became a serious invasive weed. This study assessed the quantitative and qualitative status of plant community richness and diversity in areas invaded by L. camara in the Siwalik Hills (Himachal Pradesh, India), and explored allelopathy as a possible mechanism of interference. We measured species diversity, richness and evenness of the vegetation in areas invaded and uninvaded by L. camara. Allelopathic effects of L. camara rhizosphere soil and litter were assessed against two native plants-Achyranthes aspera (a herb) and Albizia lebbeck (a tree). Density, biomass and indices of diversity, richness and evenness were reduced by L. camara, indicating a significant alteration in composition and structure of native communities. Seedling growth of the test species was reduced in L. camara rhizosphere- and litter-amended soil. The inhibitory effect was ameliorated by the addition of activated charcoal, indicating the presence of organic inhibitors (quantified as phenolics) in the soil. Lantana invasion greatly reduces the density and diversity of the vegetation in the invaded area, and chemical interference of its litter plays an important role in invasion.

The Influence of Avian Biodiversity and a Weedy Understorey on Canopy Arthropod Assembly

Identifying the factor causing species decline from a multitude of potential disturbances is essential for successful management. Invasive species are often drivers of decline, either through direct effects such as recruitment limitation, or through indirect effects such as habitat modification that facilitate biota changes in other taxa. In this study, we tested the importance of bird predation on arthropods in eucalypt canopies in wet sclerophyll forest that had been invaded by the understorey weed Lantana camara. A strong top-down effect is in agreement with studies that show elevated numbers of insectivorous birds, such as the despotic bell miner, Manorina melanophrys, reduce damaging herbivorous insect numbers and their effect on tree health. Abundance, order and family composition were compared among sites, feeding guilds, among the presence and absence of a despotic bird, and among presence and absence within sites, using a three-way nested Multivariate Analysis of Variance (MANOVA), and tested our representation of insect feeding guilds with rarefaction curves. In total, we found arthropods from 20 families on eucalypt trees, 16 where bell miners were present and 18 where they were absent (a sampling efficiency of 78% and 92% of families based on the Chao-I index). Overall, there was a difference in the abundance of insects in areas where bell miners were present (n = 181), and where they were absent (n = 67). There was also a difference in the families present in areas with bell miners and without them. Under some conditions, despotic birds may not change the insect canopy community. Further studies should examine the effects of a despotic bird on the insect canopy community in a variety of conditions and throughout their range.

Synthesis and in vitro anticancer studies of novel C-2 arylidene congeners of lantadenes

The antitumor pentacyclic triterpenoids, Lantadene A (1) and B (2) were isolated from the leaves of weed Lantana camara L. (Verbenaceae) and were structurally transformed to bioactive intermediates 3–6. The Claisen–Schmidt reaction of 22β-hydroxy-3-oxoolean-12-en-28-oic acid (5) with requisite aldehydes afforded 2-arylidene-22β-hydroxy-3-oxoolean-12-en-28-oic acids (7–16). The compounds were evaluated for their in-vitro anticancer activity by National Cancer Institute (NCI), USA and some of these compounds showed marked cytotoxicity in micromolar range. The mean graph midpoint (MG_MID) value of compound 3 (MG_MID −5.69) was higher than standard drug cisplatin (MG_MID −5.66) while comparable in case of compound 12 (MG_MID −5.52). The NCI's COMPARE molecular mechanistic analysis showed that these compounds were in significant correlations with activity patterns of mechanistic set of compounds (PCC ≥ 0.60).

Reduced Lantadenes A and B: semi-synthetic synthesis, selective cytotoxicity, apoptosis induction and inhibition of NO, TNF-α production in HL-60 cells

The aim of this study was to investigate the effect of pentacyclic triterpenoids-reduced Lantadenes A (3) and B (4) on the cytotoxicity, stimulation of apoptosis and regulation of transcription factors in HL-60 cells. The 3 and 4 are the minor compounds of weed Lantana camara L. (Verbenaceae) and were prepared semi-synthetically in single step by reducing Lantadenes A (1) and B (2) under microwave irradiation with yield of 98–99 %. The 3 and 4 demonstrated selective cytotoxicity against HL-60, MCF-7, HSC-2, and HCT-116 cancer cell lines (IC50 1.2–6.4 μM) and were found non-toxic toward normal cells (VERO) with IC50 >50). The compounds 3 and 4 (15 μM)-induced apoptosis by activation of caspase-3 and bax, along with significant decrease in expression of NF-кB (p-65) and bcl-2 in HL-60 cells. The compounds 3 and 4 at 15 μM significantly suppressed the production of nitrite, TNF-α, and iNOS gene expression in HL-60 cells. The results suggested that reduced Lantadenes A and B have the potential to be developed as anticancer agents.

Comparative Analysis by GC-MS and in vitro Antimicrobial Activity of the Essential Oils of Noxious Weed (Lantana camara L.) from Western Ghats Region of North West Karnataka, India

The essential oils obtained by hydro distillation from the leaves and flowers of Lantana camara L. (Verbenaceae) and were analyzed by GC-FID and GC-MS. A total of fifty-nine compounds have been identified comprising 91.8% (leaves) and 95.7% (flowers) of the volatile constituents. The leaves essential oil contained α-zingiberene (13.4%), γ-curcumene (11.7%), (β-caryophyllene (10.6%), ar-curcumene (5.6%), 1,10-di-epi-cubenol (5.1%), (β-curcumene (4.9%) and caryophyllene oxide (4.8%) as the main components whereas the flowers essential oil was dominated by (β-caryophyllene (21.7%), ar-curcumene (20.6%), γ-gurjunene (19.6%), γ-curcumene (10.2%) and (β-curcumene (6.5%) as the major constituents. Both the oils were screened for their antimicrobial activity by tube dilution method against six Gram-positive, eight Gram-negative bacteria and three fungi. The organism Micrococcus flavus (Gram-positive bacteria) was found more susceptible to the leaves and flowers oils with MIC value of 0.06±0.01 mg/mL and 0.26±0.03 mg/mL, respectively. The leaves and flowers oils were found to be active against Proteus mirabilis at a concentration of 0.83±0.13 mg/mL and 0.47±0.07 mg/mL, respectively. The microorganism Aspergillus niger was found susceptible to the flowers oil with MIC of 0.22±0.04 mg/mL, while Penicillium chrysogenum was susceptible at a concentration of 0.18±0.04 mg/mL.

Interaction BetweenUroplata girardi(Coleoptera: Chrysomelidae) andOphiomyia camarae(Diptera: Agromyzidae) on a Shared HostLantana camara(Verbenaceae)

Multiple releases of insect agents intended to target a single plant pest species could result in competitive interactions that in turn might affect the community structure of the phytophagous insects. Two leaf-feeding biological control agents, Uroplata girardi Pic (Coleoptera: Chrysomelidae) and Ophiomyia camarae Spencer (Dipetera: Agromyzidae), were released against the weed Lantana camara L. (Verbenaceae) in South Africa in the 1970s and 2001, respectively. Since the population explosion of O. camarae in 2005, a decline of U. girardi populations had been observed in KwaZulu-Natal (KZN) humid coast, leading to speculation that negative interaction may be operating between the agents. The study therefore was conducted to determine the competitive effect of O. camarae on U. girardi. The study showed that 76% of O. camarae larval mines were formed on uninfested (clean) compared with only 24% formed on U. girardi-infested leaves, suggesting that the fly chose to lay more eggs on clean leaves. Almost the same number of U. girardi larval mines was formed on both O. camarae-infested and clean leaves, indicating that U. girardi females in this case oviposited indiscriminately on the two types of leaves. The survival of U. girardi was 53.8% when reared on clean leaves compared with only 14.6% survival on O. camarae-infested leaves. At the end of the sampling period, densities of U. girardi was over two times higher in single-species than in combined-species treatment. Releasing both agents together did not significantly affect O. camarae densities during the sampling period. In the field, O. camarae densities increased rapidly from spring to autumn, whereas those of U. girardi remained consistently low during the same period. The bias toward oviposition on clean leaves in O. camarae enables its larvae to avoid unfavorable encounters with U. girardi larvae, thus enhancing its development and survival. The apparent inability of U. girardi to distinguish between suitable and unsuitable leaves for oviposition could compromise the fitness of this beetle, and this could explain the suppression of U. girardi populations during summer when O. camarae populations begin to increase rapidly. This study provides evidence for an asymmetric interaction between two introduced agents, and therefore highlights the importance of conducting interaction studies on agents with extensive niche overlap before their release into the environment.

The invasive weed Lantana camara increases fire risk in dry rainforest by altering fuel beds

Berry ZC, Wevill K &amp; Curran TJ (2011). The invasive weed Lantana camara increases fire risk in dry rainforest by altering fuel beds. Weed Research51, 525–533.SummaryThe invasive weed, Lantana camara, dominates numerous tropical and sub‐tropical ecosystems and affects many aspects of ecosystem functioning, one of them being susceptibility to fire intrusion. The process by which L. camara might alter fire regimes in dry rainforest was examined by considering two potential mechanisms: (i) by being more ignitable than native species or (ii) by altering the structure and distribution of biomass to facilitate fire spread. We hypothesised that L. camara might alter fire regimes by both mechanisms. Measurements of leaf dry matter content, twig dry matter content and burn durations in laboratory trials implied that L. camara was less ignitable than native dry rainforest species. Fuel bed depths, leaf litter depths, percentage cover by fuels and amount of medium‐size class fuels were higher in dry rainforest invaded by L. camara than in non‐invaded forests. This suggests that the mechanism by which L. camara alters the fire regime in dry rainforest is by shifting the distribution of available fuels closer to the ground and providing a more continuous fuel layer in the understory. Management should focus on targeting L. camara removal around forest edges adjacent to frequently burned savannas and in areas of high conservation value.