Microhabitat specialization in a species-rich palm community in Amazonian Ecuador

1 Relationships between microhabitat variables (altitude, inclination, topographic position, drainage, canopy height) and the distribution and abundance of palms and palm-like plants in 50 ha of old-growth terra firme rain forest in the Yasuní National Park, lowland Amazonian Ecuador, were examined using 118 20 × 20 m plots laid out in a stratified random design.
2 If microhabitat niche differentiation is important for maintaining the species richness of the community, then (i) the distribution of the palms will be strongly influenced by microhabitat heterogeneity and (ii) palms of similar growth form will show antagonistic microhabitat relationships.
3 Mantel and cluster analyses showed that palm species distributions were strongly structured by topography. The main difference in species composition was between plots in the bottomland and plots on the upper slopes and hill tops.
4 Logistic and logit analyses showed that 20 of the 31 palm and palm-like taxa analysed had distributions that were significantly related to the microhabitat variables measured, mainly to topography but also to drainage and canopy height.
5 Spatial autocorrelation in the overall community structure was not explained by the microhabitat variables. Analyses of distributions or abundances of single species showed neighbourhood effects for seven taxa.
6 Antagonistic patterns of microhabitat preferences were recognizable among some species pairs of small palms, medium-sized palms and palm-like plants, but not among canopy palms.
7 It is concluded that microhabitat specialization is an important factor in maintaining the diversity of this palm community, while mass effects might also be important.     

Forest fragmentation effects on palm diversity in central Amazonia

1 The effects of fragmentation on quantitative measures of floristic diversity in a palm community were examined in the Biological Dynamics of Forest Fragments study area in central Amazonia. Three 1-ha, three 10-ha, two 100-ha and three continuous forest reserves, distributed among three sites, were surveyed. In each reserve, 10 20 × 20 m plots were sampled, resulting in a total of 110 plots representing 4.4 sampled hectares.
2 The taxon composition of this palm community was dominated by stemmed, understorey palms. A total of 23 225 individuals from 36 taxa was recorded; five of the taxa were not sampled in continuous forest.
3 Taxa richness did not vary across reserve size or sites unless taxa not sampled in the continuous forest were removed from the analysis. Smaller forest fragments then harboured fewer taxa in the seedling stage than large forest fragments or continuous forest, despite the short time since isolation (10–15 years). There was a significant effect of location on the number of taxa per plot for all life stages, but only seedling and total were significantly affected by reserve size.
4 Reserve size did not affect the Shannon and Evenness indices. Reserves of similar sizes were floristically more similar than reserves of very different sizes.
5 Palms are important for the structure and composition of the forest. Their conservation may require the establishment of a number of large reserves.     

Productivity and management of Phytelephas aequatorialis (Arecaceae) in Ecuador

Phytelephas aequatorialis is endemic to western Ecuador. Vegetable ivory (tagua, the hard endosperm) and leaves for thatch (cade) are harvested from the palm and commercialised. Export of vegetable ivory from Ecuador reached a value of 14 million US$ in 2011, making it the second most important product from native palms in the country. Vegetable ivory and leaves are harvested mainly from the wild, although the palm is occasionally cultivated. Most seeds harvested for vegetable ivory are collected from the ground. In times of high demand, however, some harvesters collect immature infructescences; these young seeds are of inferior quality and unsuitable for the fabrication of tagua discs for export. Premature harvest reduces the amount of fully mature, high‐quality seed leading to resource limitation for the processing industry that already is unable to satisfy international demand. Fruit production in lowland agroforestry systems strongly correlates to the level of exposure to light. The development of infructescences takes 3 years in the lowlands (≤93 m a.s.l.) and over 4 years on the Andean slopes at around 1400 m a.s.l. Data from 365 tagged individuals show that male palms produce significantly more leaves than female palms and palms growing in the shade produce fewer, but longer and higher quality leaves for thatch. Leaf harvest has little impact on leaf production, but substantially reduces fruit production. Natural regeneration of Phytelephas populations in pastures is negatively affected, rendering the survival of these populations problematic. Sustainable use and commercialization of the two partially exclusive and locally competing products tagua (vegetable ivory) and cade (leaves for thatch) must be carefully designed. Application of unsustainable practices in the harvest of seeds and leaves, population decline in pastures, and resource limitation in the processing industry represent the main challenges in the sustainable use of this valuable palm species in the future.     

Ecological methods for adult populations of Oryctes rhinoceros (Coleoptera, Scarabaeidae)

ABSTRACT. 1. For comparing assessment methods, O.rhinoceros (L.) populations were monitored in five 30–50 ha plots in southern Luzon, Philippines. No consistent correlations were found between number of beetles caught in traps, amount of palm damage and number of breeding sites. Apparently, plots were too small to account for fast dispersal of beetles.
2. Coconut cap traps baited with ethylchrysanthemumate attracted O.rhinoceros adults searching for breeding sites. Several factors were identified influencing catches but trapping was found to be unsuitable for accurately assessing pest populations.
3. A new method which gives estimates on the monthly number of O.rhinoceros attacks on coconut palms, was tested in the Maldives. Palms are climbed about once a year and the sequence of fronds, the number and the position of beetle cuts are recorded.
4. Reduction with age of the length of three teeth on the fore tibia of O. rhinoceros adults was studied in the Philippines. The data was insufficient to obtain a clear correlation between age and length of teeth.
5. The observations indicated that in the Philippines after leaving their site of pupation, O.rhinoceros adults spend about 5 weeks feeding on coconut palms. This is followed by a period of about 7 weeks in breeding sites and, on occasion, additional visits to palms. With these estimates it was possible to relate palm damage records with numbers of feeding adults.     

Effects of simulated N deposition on understorey vegetation of a boreal coniferous forest

1. We report the short-term effects of simulated nitrogen (N) deposition on the understorey of a boreal forest in northern Sweden. Doses of ¹⁵N double-labelled NH₄NO₃ (0·5, 12·5, 25·0 and 50·0 kg N ha^–1) were applied to 1 m² plots in the summer of 1995 and plants were harvested the following autumn.
2. No significant treatment effects were found in either above- or below-ground biomass which was distributed as follows: the ericaceous shrub Vaccinium myrtillus contributed 76%, the grass Deschampsia flexuosa 4%, and the bryophytes Dicranum majus and Pleurozium schreberi 20%.
3. The recovery of applied N in these species was 24, 27, 27 and 32% of the 0·5, 12·5, 25·0 and 50·0 kg N ha^–1 applications, respectively, and thus the recovery increased with the N dose.
4. In the 0·5 kg N ha^–1 treated plots, the highest concentrations of fertilizer-derived ¹⁵N were found in the bryophytes, while in plots given the three higher N applications, leaves of D . flexuosa had the highest concentrations.
5. N application resulted in elevated concentrations of free amino acid N, which indicate increased storage of N in plant tissues. Furthermore, the N application resulted in increased damage to V . myrtillus by natural enemies. The severity of disease caused by two foliar parasitic fungi showed a clear numerical response to N treatment, as did the amount of herbivory as a result of Lepidoptera larvae.     

Dispersal by bagworm larvae, Metisa plana: effects of population density, larval sex, and host plant attributes

Abstract 1. The work reported here investigated the incidence of dispersal by bagworm larvae Metisa plana (Walker) (Lepidoptera: Psychidae), a species with apterous females and winged males.
2. A mark–recapture study conducted in a plantation of oil palm revealed that a significant proportion of larvae undertakes multiple episodes of ballooning, and suggested that ballooning represents a strategy for foraging both within and between hosts.
3. Experiments conducted in a controlled cage environment indicated that increasing population density and defoliation of oil palm both promote dispersal by larvae.
4. Neonatal larvae typically remained on the host where they emerged, indicating that pupation site of late-instar females influences the distribution of their progeny, and suggesting a high level of genetic relatedness in localised bagworm populations.
5. Density-dependent dispersal may generate relatively uniform distributions of M. plana in plantations of oil palm, by simultaneously stabilising populations on heavily infested palms and redistributing larvae on lightly infested palms.
6. The rate of ballooning was greater for female than for male larvae, possibly resulting from the sex-specific impact of population density on reproductive success or from late-instar females seeking suitable oviposition sites for their future progeny.     

The uniqueness of palms

Palms build tall trees entirely by primary growth in a way that limits their growth habit, but not their capacity for continued stem development. They achieve massive primary stature because of distinctive features of leaf development, stem vasculature and anatomical properties. They exhibit several record features of leaf and seed, and inflorescence size and leaves of great complexity. A marked ability to generate new roots allows them to be transplanted easily. As climbing plants they develop the longest unrooted stems in which there are, paradoxically, anomalous features of vascular construction compared with tree palms. It is here claimed that they are the world's longest lived trees because stem cells of several kinds remain active in differentiated tissues throughout the life of the palm. Absence of physiological dormancy may be related to this property, together with inability to withstand freezing temperatures that would cause irreversible cavitation of tracheary elements. This largely restricts them to the tropics, for which they are emblematic organisms. In these biological features palms are indeed unique organisms.  © 2006 The Linnean Society of London, Botanical Journal of the Linnean Society , 2006, 151 , 5–14.     

Effects of palm heart harvesting on avian frugivores in the Atlantic rain forest of Brazil

1. It has been suggested that palm fruits are keystone resources for frugivores in tropical rain forests, but no study has addressed this hypothesis. The effects of the harvesting of a dominant palm tree Euterpe edulis were studied over 2 years in the Atlantic forest of Brazil.
2. The abundance of 15 large frugivorous birds from five families (Ramphastidae, Cracidae, Cotingidae, Trogonidae and Psittacidae) was estimated using unlimited distance point counts (IPA) and encounter rate.
3. Although all species studied are known to eat Euterpe fruits, only one Cotingidae ( Carpornis melanocephalus ) and one Ramphastidae ( Ramphastos vitellinus ) were negatively affected by the removal of this palm from the forest.
4. This result indicates that Euterpe palms in the lowland forests do not fulfil the role of keystone species, because they bear ripe fruits during the period of peak overall fruit availability and because birds may switch their diets to other food sources when palms are removed.
5. Palm-heart exploitation is not recommended in small forest areas, nor in areas where E. edulis bears fruit during the period of overall fruit scarcity. Only long-term monitoring can evaluate the responses of the bird and mammal communities to the harvesting process.     

Phytoplasma distribution in coconut palms affected by lethal yellowing disease

Lethal yellowing (LY), the most devastating disease affecting the coconut palm in America, is caused by phytoplasmas known to be distributed in different parts of infected plants. However, no comprehensive reports exist on the phytoplasma distribution. This study refers to the detection of LY phytoplasma DNA using PCR in different coconut plant parts, throughout the development of the disease. Sample analysis of positive palms taken at different stages of disease development (either symptomatic or symptomless) showed differences in the percentage of LY detection between plant parts. Some parts showed a very high level of LY DNA (stem, young leaves, inflorescences, stem apex and root apex), low levels were found in the intermediate leaves and roots without apex, whereas no LY phytoplasma DNA was detected in mature leaves. The detection percentage of LY phytoplasma DNA was lowest in symptomless‐infected palms for all parts, except the stem, where phytoplasma accumulations were consistently detected. This pattern of detection among parts is consistent with the hypothesis that phytoplasmas move from photosynthate source tissues to sink tissues via the phloem mass flow process. The accumulations in the (lower) stem, prior to the appearance of symptoms, suggest that this part of the palm is where phytoplasmas first move from leaves after foliar feeding by vectors and in which they probably multiply and distribute to other palm parts, including roots. Embryos from infected palms were analysed by nested‐PCR and 28% of 394 embryos were positive. Phytoplasma DNA was detected in embryos from fruit on any of the fruiting bunches regardless the age, but no pattern of quantitative distribution throughout the bunch developmental stages was observed. Germination of seeds from LY‐positive symptomatic palms was 58% and from LY‐negative symptomless palms were 71%. No phytoplasma was detected in seedlings tested from both symptomatic and non‐symptomatic palms. Seedlings tested after 2 years did not develop LY symptoms or eventually died.     

Palm heart harvesting in the Brazilian Atlantic forest: changes in industry structure and the illegal trade

1. Until the late 1960s, Euterpe edulis was the most important edible palm species in the Brazilian markets. Since then, overharvesting of natural stands and the limited scope of plantations have caused the industry to shift to the multistemmed E. oleracea from the Amazon river estuary.
2. As a result of the relocation of the industry, the structure of the palm harvesting industry has changed and illegal trade has continued to exploit the remaining natural stands of E. edulis .
3. It is suggested that, to avoid the total harvesting of E. edulis and to achieve sustainable management of the palm heart, it will be necessary to diversify the local economy, create incentives for small land owners to improve their management practices, while keeping their competitiveness against the illegal trade, create the incentive of new sources of palm hearts and create a 'green stamping' for management palms.
4. Transformation of the illegal structure of the palm heart industry is probably the only solution to avoid the total depletion of the wild stands of E. edulis .     

Multi-species territoriality and dynamic of neotropical forest understorey bird flocks

1. Eleven contiguous mixed-species bird flocks, with colour-banded individuals, were monitored continuously during 3 years in a 132-ha study area of primary rainforest in French Guiana.
2. Flock members were divided into six categories according to their flocking propensity and occurrence: 10 core or permanent species and 56 regular, occasional or incidental species. Each core species was represented by a single breeding pair with their fledglings and extra 'floaters' (unmated subadults and adults).
3. Flock home ranges overlapped slightly, but were communally defended by all core species in areas of overlap. Their size varied from 3·2 to 14·3 ha and was inversely correlated with vegetation density, but not flock size or species composition.
4. Flock number, size and composition, as well as boundaries were highly stable between seasons and years. Each flock had a single permanent gathering site and bathing site in late afternoon, the latter sometimes shared by 2–3 flocks.
5. Core species produced 0·18–0·73 fledglings per pair per year, which stayed in their natal flock for 200 to over 421 days. Then, these individuals usually moved between two and six different flocks, sometimes for up to 3 years, before finding a mate and a flock where they could settle and breed. Once breeding, they probably remained for life in the same flock. The mean annual survival rate was at least 0·75.
6. This highly evolved and stable organization, associated with a low breeding success and high survival rate was a critical factor maintaining low species density, delayed reproduction and a proportion of floating individuals buffering population fluctuations.
7. These social groups with their multi-species territoriality and co-evolved roles of flock members were similar to those described elsewhere in South America. They seem to be a general phenomenon in neotropical lowland rainforests.     

Fractionation and bioaccumulation of copper and zinc in wetland soils of the Niger Delta determined by the oil palm

Abstract

The concentration, mobility, bioavailability, distribution and associations of two essential micronutrient elements (copper and zinc) to the oil palm in wetland soils of the Niger delta region of Nigeria was assessed by means of chemical fractionation analysis. The water soluble and plant available fractions were introduced into the sequential extraction scheme. Also assessed were the bioaccumulation (concentration and distribution) of these metals in the leaves and fruits of the oil palm of various ages found around the soil profiles. Copper was obtained more in the amorphous Fe-oxide fraction (151.05 mg kg^?1), but evenly distributed in the exchangeable component (16.16%) with a maximum value of 126.6 mg kg^?1. The water soluble and plant available fractions had 16.15 and 7.54% distribution of Cu respectively. Zinc had 2.35 and 30.42% distribution in the water soluble and plant available fractions respectively. The lowest mean amount of Cu (1.33 mg kg^?1) was determined in the leaves of palms of ages 15–32 years. Palms greater than 60 years had the highest mean concentration of copper (3.91 mg kg^?1) in the leaves while the endosperm (kernel) of palms between 2 and 10 years had concentration of 9.07 mg kg^?1. The fibrous oily mesocarp had the highest amount (16.78 mg kg^?1) of copper in the older palms (>60 years). Similarly, Zn was dominant in the older palms with a mean concentration of 187.14mg kg^?1 obtained in the endosperm (kernel). The bioaccumulation pattern of both metals by the palms irrespective of age and the fractionation analysis revealed sufficient bioavailable and reserved amounts of Zn and Cu in the wetland soils.     

Stilt Root Structure in the Neotropical Palms Iriartea deltoidea and Socratea exorrhiza1

Many arborescent palms develop a stilt root cone that provides increased mechanical support on steep hillsides, better root aeration under waterlogged conditions, resprouting after mechanical damage, and rapid stem elongation. However, for most species the role of stilt roots is not well understood. We determined how palm size and slope inclination affected the structure of stilt roots in the neotropical palms Iriartea deltoidea and Socratea exorrhiza. We expected palm height to be lower on steep slopes because the effectiveness of root support could decrease as slope inclination increases, and thus, the structure of the root cone would vary mostly with slope. Alternatively, if stilt root development is determined by palm size, their production should match stem height, with taller palms having larger cones. We measured the stilt root cone of 31 Iriartea and 36 Socratea palms in San Ramón Biological Reserve and Golfito Wildlife Refuge, Costa Rica. We divided the cone into five variables (horizontal projections of the cone base and stilt root height up and down the slope, and width of the cone base), from which we extracted the first two principal components and used them to measure the effects of slope and palm size on stilt root structure. We found stilt roots to be determined by palm size, not by slope conditions. Stilt roots matched palm size, with larger palms having taller and larger cones, maintaining stability under diverse slope conditions.     

The impact of utilization of palm products on the population structure of the vegetable ivory palm (Hyphaene petersiana,arecaceae) in North-Central Namibia

Indigenous trees fulfil many subsistence and economic needs in north-central Namibia.Hyphaene petersiana provides a range of products which contribute to most aspects of people’s livelihoods. Of particular importance is its income-generating capacity through the use of palm leaves for basket production and the sale of liquor distilled from the fruits. This study investigates the population structure ofHyphaene petersiana in two areas of different human and livestock densities. Data were recorded for height class distribution, basal diameter of mature, stemmed individuals and sex ratios. These parameters of population structure indicate a reduction in the recruitment of mature palms and an increase in single-stemmed, vegetatively reproduced palm suckers of the smallest size class (0.5 m). This trend is more pronounced in the site with greater human and livestock population densities. It appears to be related to high recorded levels of browsing by livestock of juvenile, unstemmed palms, despite the unpalatability of palm leaves. This acts to prevent recruitment into larger size classes and increase the compensatory growth of palm suckers, the latter being enhanced due to reduced competition through the prior removal by grazing animals of grasses and other herbaceous species. Accompanying this heavy pressure on juvenile palms are destructive uses of mature, stemmed palms, including their felling for construction purposes and tapping for palm wine. With regional human population increase, exacerbated by a recent trend to privatise land and raise pressure on remaining communal resources, it is possible that these destructive uses of mature palms will increase to unsustainable levels. Concern is thus expressed in this study regarding the long-term viability ofHyphaene petersiana populatiops in this area.     

Population Structure and Life Cycle of Borassus aethiopum Mart.: Evidence of Early Senescence in a Palm Tree1

As with other plants having a relatively simple morphology, solitary palms are useful biological models for studying the life histories of long-lived plants. In the first study to investigate the life history of Borassus aethiopum, a widespread dioecious palm growing in African savannas, we found that: (1) the number of leaves increased up to reproductive maturity and then decreased during the reproductive period, while height increased throughout life; (2) female fecundity, measured as the number of seedlings within a few meters under the female canopies, decreased markedly in old individuals with few leaves; and (3) height distribution was strongly bimodal. This bimodality was due to variations in the stem elongation rate during the life of the palm and the accumulation of adults with low mortality rates in the taller height classes. The observed pattern of fecundity and number of leaves in relation to height clearly suggests a senescence period that began just after sexual maturity and appeared to be protracted. Comparisons between the life history of B. aethiopum and the life histories of some forest palms showed that environmental conditions cannot in themselves explain the various palm life histories.     

Effects of river red gum, Eucalyptus camaldulensis, litter on golden perch, Macquaria ambigua

Aquaria with added river red gum, Eucalyptus camaldulensis , litter became hypoxic, with decreased pH and contained up to 30 mg 1⁻¹ tannin and lignin. Survival of golden perch, Macquaria ambigua , larvae in aquaria treated with a simulated annual litter density of 450 g m⁻² for 72 h was 14·9% for 15-day-old larvae and 0% for 8-day-old larvae. A litter density of 1223 g m⁻² resulted in total mortality for both age groups of larvae. Aeration increased survival of larvae to a minimum of 68·8% in 1223 g m⁻² litter treatments compared to 89·8% in aerated controls and 86·8% in non-aerated controls. A kinetic behavioural assay was used to detect alarm responses in golden perch larvae and juveniles exposed to leachates from river red gum bark, leaves and wood. Eight-day-old larvae exposed to bark and wood leachates (0·001–10 g 1⁻¹) exhibited an initial period of hyperactivity, followed by a concentration-dependent decrease in spontaneous activity. Larvae exposed to leaf leachates displayed only a decrease in spontaneous activity. Four-month-old juveniles exposed to wood leachates were also initially hyperactive, then progressively developed mild hypoactivity at increasing leachate concentrations. Juveniles exposed to wood leachates at 20g 1⁻¹ for 30min suffered 97·5% mortality in 96 h. Wood leachates induced dose-dependent lamellar fusion, epithelial dissociation and necrosis in the gills. The presence of toxic leachates and low oxygen availability in flooded river red gum forests may make these habitats unsuitable as nursery areas for native fish.     

Natural enemy ravine revisited: the importance of sample size for determining population growth

Abstract. 1. The population growth of three aphid species, Metopolophium dirhodum (Walker), Rhopalosiphum padi (L.), and Sitobion avenae (F.), on winter wheat, was analysed by regression. The calculations were based on censuses of aphids made in 268 plots at 3- or 7-day intervals for 10 years on leaves and 6 years on ears. The calculations were made separately for each plot each year, then repeated on the pooled data from all plots monitored in a year.
2. At the level of individual plots, no population growth was detected at very low densities. At high densities, the populations grew exponentially and the growth rates did not decrease with increasing aphid density.
3. Significant growth was always detected in the pooled data. These growth rates decreased significantly at the highest densities. Field estimates of the intrinsic rate of increase derived from these data ranged from 0.010 to 0.026 for M. dirhodum , 0.0071–0.011 for R. padi , and 0.00078–0.0061 and 0.0015–0.13 for S. avenae , on leaves and ears respectively .
4. The apparent lack of growth in the individual plots at low densities is attributable to small sample size. It is concluded that the natural enemy ravine in the population dynamics of cereal aphids, identified by Southwood and Comins (1976), is a consequence of low population densities at which population increase is undetectable unless very large samples are taken.     

Edge effects on palm diversity in rain forest fragments in western Ecuador

At the edges of tropical rain forest fragments, altered abiotic and biotic conditions influence the structure and dynamics of plant communities. In Neotropical rain forests, palms (Arecaceae) are important floristic and ecological elements. Palms’ responses to edge effects appear to be idiosyncratic and to depend on the level of disturbance at edges. This paper explores how variation in forest structure at the edges of two old-growth forest fragments in a tropical rain forest in western Ecuador affects palms of different species, life-forms, and size classes. We investigate (1) how edge effects influence the relative proportion of palm adults and juveniles, (2) how distance from the forest edge affects palm density and species richness, (3) how altered forest structure along edges affects palm density. We found that at edges (1) palm communities had a lower proportion of adults relative to juvenile individuals compared to continuous forests, (2) the density of two species of palms and the overall species richness of the palm community tended to decrease toward the edges within forest fragments, and, (3) altered forest structure decreased the density of adult palms. Hence, edge effects on palms were controlled by the degree of modification of the forest structure, and by species responses to edge-related disturbance.     

Life cycle and population dynamics of Trochosa terricola Thorell (Araneae: Lycosidae) in a Norfolk grass heath

Abstract. 1. The population of the lycosid Trochosa terricola Thorell was sampled from April 1973 to August 1975 at Weeting Heath NNR, a Breckland grass heath.
2. Four sampling methods were compared for efficiency. Hand searching gave density estimates between 38.3 and 70.1% of heat extraction.
3. The temperature range in the sward at +1 cm was –5°C to 39°C with January and July means of 3.2°C and 17.4°C.
4. Eight male and nine female instars were determined and the life cycle extended over 2 or 3 years.
5. Adults were nocturnal but the juveniles diurnal. An annual diplochrone activity pattern was observed for adult males.
6. The horizontal distribution within the sward was aggregated, the structure and microhabitat being important determining factors. The population density was greater in moist, young Festuca spp. tussocks. An equation relating population density to habitat characteristics was derived.
7. The overall population density ranged from 14.0 m^-2 to 76.0 m^-2 and was maximal in autumn after breeding. The population biomass was greatest during autumn (291.2 mg d.wt m^-2).
8. Mean number of juveniles emerging from an egg sac was 77.3 (first sac) and 38.0 (second sac). The natality in 1973 was 66.8 individuals m^-2.
9. The survivorship curve until maturity varied between types I and III in different years.
10. The population dynamics were compared and are discussed in the light of other data. The variable population characteristics suggested that Den Boer's "spreading of risk" theory applied to the T.terricola population.     

Stem rots of oil palm caused by <Emphasis Type="Italic">Ganoderma boninense</Emphasis>: Pathogen biology and epidemiology

Oil palm (Elaeis guineensis Jacq.) has been grown in Papua New Guinea since the early 1960s. The most important disease of oil palm in PNG is a stem rot of the palm base. This is the same disease that constitutes a major threat to sustainable oil palm production in SE Asia. Investigations into the causal pathogen have revealed that the stem rots in PNG are caused predominantly by the basidiomycete Ganoderma boninense, with a minor pathogen identified as G. tornatum G. tornatum was found to have a broad host range whereas G. boninense appears to be restricted to palms. The population structure of G. boninense was investigated using inter-fertility studies between isolates collected from basal stem rots on oil palm. Although the G. boninense field populations are predominantly comprised of distinct individuals, a number of isolates were found that share single mating alleles. This indicates that out-crossing had occurred over several generations in the resident or wild population of G. boninense prior to colonization of oil palm. No direct hereditary relationship between isolates on neighbouring diseased palms was found, although an indirect link between isolates causing upper stem rot and basal stem rot was detected.