The biogeographical distribution of microfungi associated with three palm species from tropical and temperate habitats

The microfungi of three palm species were investigated in their natural habitats and in habitats where the palms were cultivated outside their natural ranges. The palms that were selected differed in their habitats and ecology. Archontophoenix alexandrae is endemic to tropical rainforests in Australia, Cocos nucifera is pan‐tropical and Trachycarpus fortunei occurs in warm‐temperate China. Different assemblages of fungi were found in association with palms in temperate regions as compared to those in tropical regions. These differences were more related to climatic influences than to the hosts sampled, as few fungi were host‐species specific. The status of the hosts at the site, i.e. indigenous or introduced, and the degree of disturbance of the habitats within which the palms grew were also influential. When sampled in its natural habitat, Archontophoenix alexandrae had a distinct palmicolous mycota typical of other palms in tropical rainforests. Outside of the palm’s natural habitat, a widely different mycota were recorded that comprised tropical species of a more plurivorous nature. A similar plurivorous assemblage characterized the fungi associated with Cocos nucifera, probably due to the palm’s long history of cultivation. Similarly, plurivorous, but temperate or widespread fungi were associated with Trachycarpus fortunei, both within and outside of its natural habitat. This palm is also highly cultivated. A reduction in palm fungi associated with palms in disturbed habitats has implications for conservation of these fungi. However, it is acknowledged that the data for fungal diversity and distribution is incomplete and fragmentary.     

Localisation of coconut foliar decay virus in coconut palm

Coconut foliar decay virus (CFDV) occurs at a very low concentration in coconut palm. A 1203 nucleotide segment of the sequenced encapsidated circular single-stranded 1291 nucleotide CFDV-DNA has been amplified and transcribed for use as a ³²P cDNA probe for the virus. A rapid method for the extraction of DNA from coconut palm has been devised for a dot-blot hybridisation assay using this probe. An alternative non-radioactive probe has also been developed for future use in CFDV diagnosis. CFDV-DNA was shown to be distributed unevenly in a range of infected palms, necessitating the use of multiple sampling to reliably detect infection in diagnostic tests. Viral DNA was detected in symptomatic and asymptomatic palms of both high and low susceptibility, in disease-free tolerant cultivars, and in palms in remission from disease. Within the same palm, detectability of viral DNA varied little within leaflets, but varied more within and between fronds. CFDV-DNA was detected 6–8 months after insect-mediated inoculation, and symptoms generally appeared after another 1–4 months. In situ hybridisation of rachis tissue showed localisation of DNA within the phloem, but its distribution in the phloem was uneven. CFDV-DNA was detected in tissue adjacent to and within necrotic zones which develop into the petiolar lesions associated with the disease-specific collapse of fronds. Virus was detected in the body of the insect vector, and, where its distribution could be resolved, in the abdomen rather than the head.     

Aquatic fungi from peat swamp palms: <Emphasis Type="Italic">Unisetosphaeria penguinoides</Emphasis> gen. et sp. nov., and three new <Emphasis Type="Italic">Dactylaria</Emphasis> species

Unisetosphaeria penguinoides gen. et sp. nov. and three new species of Dactylaria are described from dead petioles and rhachides of the palms Eleiodoxa conferta and Nenga pumila (Arecaceae) collected in Sirindhorn Peat Swamp Forest, southern Thailand. Unisetosphaeria (Ascomycota) is compared with similar genera, and its placement at the family level is considered. The three new Dactylaria species (anamorphic fungi) are compared with similar species in the genus.     

Molecular Characterization and Detection of African Oil Palm Ringspot Virus

African oil palm ringspot virus (AOPRV) had been previously described as a fovea‐like virus associated with a lethal disease of African oil palm (Elaeis guineensis) in South America. The original report was based on partial sequence and a distant relationship between AOPRV and Apple stem pitting virus, Apricot latent virus and Grapevine rupestris stem pitting‐associated virus, definitive species of the genus Foveavirus, family Flexiviridae. We report the full sequence of the RNA genome of AOPRV, and demonstrate that this virus is more closely related to two unassigned virus species of the family Flexiviridae (Cherry green ring mottle virus and Cherry necrotic rusty mottle virus) than to any definitive species of the genus Foveavirus. Thus, AOPRV should be considered as a new species of the Flexiviridae until the International Committee on Taxonomy of Viruses (ICTV) resolves the taxonomic status of the increasing number of unassigned species in this family. The molecular characterization of AOPRV has provided a highly sensitive and reliable RT‐PCR assay for the early detection of AOPRV in different genotypes of African, American (E. oleifera) and hybrid oil palms.     

Occurrence of 16SrIV Subgroup A Phytoplasmas in Roystonea regia and Acrocomia mexicana Palms with Lethal Yellowing‐like Syndromes in Yucatán,Mexico

The lethal yellowing (LY) disease and LY‐type syndromes affecting several palm species are associated with 16SrIV phytoplasmas in the Americas. In Mexico, palms of the species Roystonea regia and the native Acrocomia mexicana were found to exhibit LY‐type symptoms, including leaf decay, starting with mature leaves, necrosis and atrophy of inflorescences. DNA extracts obtained from these palms could be amplified by nested‐PCR using phytoplasma‐universal primer pair P1/P7 followed by LY‐group‐specific primer pair LY16Sr/LY16Sf. Blast analysis of the sequences obtained revealed an identity of 100% for R. regia and 99.27% for A. mexicana with 16SrIV‐A strain associated with LY in Florida, USA (Acc. AF498309 ). Computer‐simulated RFLP analysis showed that the patterns for the phytoplasma DNA of the two palm species were highly similar to that for 16SrIV subgroup A strain. A neighbour‐joining tree was constructed, and the sequences of the two palm species clustered in the same clade of group 16SrIV subgroup A. The results therefore support that LY‐type syndromes observed in palms of R. regia and A. mexicana in the Yucatan region of Mexico are associated with 16SrIV subgroup A phytoplasmas.     

Biodiversity of palm fungi in the tropics: are global fungal diversity estimates realistic?

Two questions are addressed: 'How many species of fungi can occur on a single host palm?' and 'What are the implications of this for global estimates of fungal diversity?' Fungal diversity estimates found in the literature are reviewed. Data on the numbers of fungi occurring on the above-ground tissues of six individual palms in the genus Licuala in Australia and Brunei Darussalam (Borneo) are provided. A total of 189 species of fungi were isolated and/or collected from the six palms. In addition, 53 'morphospecies' of mycelia sterilia were isolated, giving a total of 242 taxa from the 2672 isolates/collections made. The three palms in Australia (sampled once) yielded 100 species (each palm supporting an average of 54.7 taxa), while the three palms in Brunei Darussalam (sampled three times) yielded 172 species in total (approximately 111.3 taxa each). The magnitude of global fungal diversity, estimated at 1.5 million species, is discussed. Our results indicate that 33 to 1 would be a more accurate estimate (than 5.7 to 1) of the ratio of host specific fungal to palm species in the tropics. We therefore propose that global estimates of fungal diversity, based on temperate studies, require revision upwards.     

Association of Copper and Zinc Levels in Oil Palm (Elaeis guineensis) to the Spatial Distribution of Ganoderma Species in the Plantations on Peat

Nutrients are essential for normal physiological processes in plants, and they play important roles in defence mechanisms against pathogens. Oil palms cultivated on peat are more prone to nutrient deficiency, especially micronutrients, and this may affect their susceptibility to Ganoderma species, the major threat to the sustainability of oil palm throughout South‐East Asia. This study was conducted to investigate the association of copper (Cu) and zinc (Zn) in mature oil palm to the spatial distribution of Ganoderma species in the plantations on peat. Foliar samples (frond 17) of oil palm from two plantations (Betong and Miri) on peat in Sarawak, Malaysia, were collected based on the spatial distribution pattern of Ganoderma, and total Cu and Zn were quantified spectrometrically. The experiment was conducted twice at a 1‐year interval. The concentrations of Cu and Zn were significantly lower in oil palms from infected areas in contrast to those from uninfected areas. In addition, oil palms in infected areas in Miri suffered Cu and Zn deficiencies. Furthermore, Cu and Zn were significantly lower in the oil palms in Miri that had higher Ganoderma occurrence, as compared to those in Betong, which had significantly higher Cu and Zn but lower Ganoderma occurrence.     

Palm Management in South America

We reviewed information on management of useful palms in South America. We documented management for 96 species, from incidental activities intended to increase populations of wild palms to the inclusion of palms in complex agroforestry systems. Two species, Bactris gasipaes and Parajubaea cocoides, are domesticated. Managed species are remarkably fewer than species used in the region, which suggests that harvesters often disregard the fate of the species they use. The best way of managing palms is to employ harvest methods that do not decimate the populations. Although a variety of harvesting techniques have been documented, overharvest is common, and mismanagement prevails – unnecessary felling of palms in order to harvest leaves or fruits is a widespread practice. Research should focus on assessing production in response to management practices, but eradicating the habit of destructive harvest is an obvious priority. Research on palm management must be combined with actions addressed to all stakeholders of the palm/humans system.     

Unique arbuscular mycorrhizal fungal communities uncovered in date palm plantations and surrounding desert habitats of Southern Arabia

The main objective of this study was to shed light on the previously unknown arbuscular mycorrhizal fungal (AMF) communities in Southern Arabia. We explored AMF communities in two date palm (Phoenix dactylifera) plantations and the natural vegetation of their surrounding arid habitats. The plantations were managed traditionally in an oasis and according to conventional guidelines at an experimental station. Based on spore morphotyping, the AMF communities under the date palms appeared to be quite diverse at both plantations and more similar to each other than to the communities under the ruderal plant, Polygala erioptera, growing at the experimental station on the dry strip between the palm trees, and to the communities uncovered under the native vegetation (Zygophyllum hamiense, Salvadora persica, Prosopis cineraria, inter-plant area) of adjacent undisturbed arid habitat. AMF spore abundance and species richness were higher under date palms than under the ruderal and native plants. Sampling in a remote sand dune area under Heliotropium kotschyi yielded only two AMF morphospecies and only after trap culturing. Overall, 25 AMF morphospecies were detected encompassing all study habitats. Eighteen belonged to the genus Glomus including four undescribed species. Glomus sinuosum, a species typically found in undisturbed habitats, was the most frequently occurring morphospecies under the date palms. Using molecular tools, it was also found as a phylogenetic taxon associated with date palm roots. These roots were associated with nine phylogenetic taxa, among them eight from Glomus group A, but the majority could not be assigned to known morphospecies or to environmental sequences in public databases. Some phylogenetic taxa seemed to be site specific. Despite the use of group-specific primers and efficient trapping systems with a bait plant consortium, surprisingly, two of the globally most frequently found species, Glomus intraradices and Glomus mosseae, were not detected neither as phylogenetic taxa in the date palm roots nor as spores under the date palms, the intermediate ruderal plant, or the surrounding natural vegetation. The results highlight the uniqueness of AMF communities inhabiting these diverse habitats exposed to the harsh climatic conditions of Southern Arabia.     

The role of beetles in the pollination of the mangrove palm Nypa fruticans

The flowers of the mangrove palm Nypa fruticans attracts a diverse array of potential pollinators. However, little is known about the pollination mechanism and which functional groups are the key pollinators. Inflorescences of nine nipa palms of different flowering stages were observed three times a day between sunrise and sunset in Thailand. The apparent entomofauna activity was recorded and all inflorescences were collected for extraction and identification of the beetle fauna. Beetles extracted from female inflorescences were measured for pollen load. In addition, thermogenesis was recorded over two days on two separate inflorescences. The most frequent visitors were species of nitidulid (genus Epuraea and the subfamily Cillaeinae) and curculionid beetles. Although they only carried small amounts of pollen grains, these groups of beetles were omnipresent. Thermogenesis peaked around 6.30 am with temperature elevations reaching 6° above ambient. The result obtained in this study are compared with those of previous studies conducted elsewhere in Thailand and in the Philippinies. The combined evidence strongly suggests a pivotal role in pollination of beetle visitors to the inflorescences of Nypa fruticans.     

Biodiversity and distribution of fungi associated with decomposing Nypa fruticans

Fungi associated with the decomposition of Nypa fruticans in Malaysia are under investigation. Forty-one fungi have been identified including 35 ascomycetes, four mitosporic fungi and two basidiomycetes. The distribution of intertidal fungi on palm structures including leaves, leaf veins, rachides, petiole bases, and inflorescences, and fungi on terrestrial parts have also been examined. No fungi were found on the leaf material, although several fungi were found on the leaf midribs, and possible reasons for this are given. Very few taxa developed on the inflorescences, but those that were present were abundant. The greatest density of fruiting structures occurred on the rachides, and the greatest diversity of fungal species occurred on the petiole bases. The terrestrial fungi differed from the intertidal fungi, although Linocarpon nipae occurred in both habitats. Reasons for the differences in fungal numbers and diversity on the various palm parts are discussed. The diversity of fungi at Morib mangrove was low when compared to previous studies on fungi on Nypa palm at Kampong Api Api in Brunei and in this study at Kuala Selangor mangrove in Malaysia.     

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.     

Molecular genetic analysis of two native desert palm genera,Washingtonia and Brahea,from the Baja California Peninsula and Guadalupe Island

The complex geological and ecological processes that have generated high levels of biodiversity and endemism in the Baja California Peninsula have been the subject of intensive study. However, relatively little is known about phylogeography of the iconic endemic palm species of this region. We therefore analyzed a total of 2,294 bp of chloroplast and 738 bp of nuclear sequence data in 169 samples of five native palm species from Baja California, Sonora and Guadalupe Island. We found that Washingtonia and Brahea palms had low levels of genetic diversity and were highly structured, with the majority of species and major geographic regions being characterized by distinct haplotypes. We also found strong support for currently recognized species in Washingtonia, but our results were less clear cut for Brahea due to haplotype sharing. Furthermore, patterns of population structure were broadly consistent with historical vicariant events such as the inundation of the Isthmus of La Paz, the formation of the Sea of Cortez, and the more recent colonization and isolation of Guadalupe Island's palms. Our findings contribute toward a growing appreciation of the complexity of plant responses to past geological changes and also provide valuable baseline genetic data on relict American palm species.     

Exploring arboreal ant community composition and co-occurrence patterns in plantations of oil palm Elaeis guineensis in Borneo and Peninsular Malaysia

The oil palm, Elaeis guineensis , is a native of West Africa and is now extensively grown in south-east Asia. In 2005, the crop covered four million ha of Malaysia. We examined the arboreal ant fauna in two oil palm plantations that had been farmed with integrated pest management practices for at least 10 yr. Having cut and examined palm fronds from 595 and 503 palms in Borneo and Peninsular Malaysia respectively, we studied diversity in ant assemblages, analysed composition of ant mosaics by stepwise use of null-models, and explored the influence of exotic vs native species on community structure. Altogether we sampled 52 species of canopy ants, of which 23 species were shared between Borneo and Peninsular Malaysia. Seventeen species in Borneo and 24 species in Peninsular Malaysia accounted for 95% of all species occurrences (SOCs). Fortysix percent of all SOCs belonged to 12 tramp ant species with pan-tropical distributions. Forty percent of all SOCs were exotic ants. Six dominant species were found in Borneo, five in the Peninsula. The three most abundant species, Anoplolepis gracilipes , Oecophylla smaragdina and Technomyrmex albipes were dominant in both sites. Three dominants were invasive species that were found on more palms than the native group. Dominant tramp species coexisted with non-dominants more often and tolerated more species of non-dominant ants than native dominants. Null model analyses indicated that species were arranged in mosaics at both the Peninsular Malaysia and Borneo sites. Dominant species showed much less co-occurrence than expected by chance, pointing towards species segregation (even in presence of introduced, invasive species). Similar results were obtained for all species. Non-dominant ants were either positively associated with their dominants, or co-occurred randomly in the presence of dominant species. In contrast, ant assemblages on palms without dominants showed species segregation.     

New costapalmate palm leaves from the Oligocene Ningming Formation of Guangxi,China, and their biogeographic and palaeoclimatic implications

New palm leaves from the Oligocene Ningming Formation are placed into the morphogenus Sabalites because of their costapalmate leaf shape. Four taxa are described on the basis of leaf compressions with cuticular structure. S. guanxiensis sp. nov. is characterised by hypostomatic leaf blades with a stout costa and a symmetrical base. Sabalites cf. asymmetricus has amphistomatic leaf blades with a long, delicate costa and an asymmetrical base. Sabalites sp. 1 has amphistomatic leaf blades with a long, massive costa and wide segments. Sabalites sp. 2 is characterized by hypostomatic leaf blades with a prominent costa and an asymmetrical base. The four new palm taxa expand our understanding of the floristic elements and features of the Oligocene Ningming flora. Together with the other three palm taxa that were previously reported from the Ningming Formation, our material indicates that the Oligocene Ningming flora had a rich diversity of costapalmate palms. The relatively high species diversity of palms and other plants corroborate that the Oligocene Ningming flora represents a warm and humid climate.     

Disruption of recruitment in two endemic palms on Lord Howe Island by invasive rats

Invasive species may have negative impacts on many narrow range endemics and species restricted to oceanic islands. Predicting recent impacts of invasive species on long-lived trees is difficult because the presence of adult plants may mask population changes. We examined the impact of introduced black rats (Rattus rattus) on two palm species restricted to cloud forests and endemic to Lord Howe Island, a small oceanic island in the southern Pacific. We combined estimates of the standing size distribution of these palms with the proximal impacts of rats on fruit survival in areas baited to control rats and in unbaited areas. The size distribution of palms with trunks was comparable across baited and unbaited sites. Small juvenile palms lacking a trunk (<50 cm tall) were abundant in baited areas, but rare in unbaited sites for Lepidorrhachis mooreana, and rare or absent in 3 out of 4 unbaited Hedyscepe canterburyana sites. All ripe fruits were lost to rats in the small fruited L. mooreana. Fruit removal was widespread but less (20–54%) in H. canterburyana. Both palms showed evidence of a reduced capacity to maintain a juvenile bank of palms through regular recruitment as a consequence of over 90 years of rat impact. This will limit the ability of these species to take advantage of episodic canopy gaps. Baiting for rat control reduced fruit losses and resulted in the re-establishment of a juvenile palm bank. Conservation of both endemic palms necessitates control (or eradication) of rat populations on the unique cloud forest summits of the island.     

Allometric estimation of total leaf area in the neotropical palm Euterpe oleracea at La Selva, Costa Rica

We estimated the magnitude of the total leaf area of the neotropical palm Euterpe oleracea and examined its allometry relative to the variation in stem height and diameter at La Selva Biological Station in Costa Rica. The allometric relationships between frond leaf area and frond length (from tip to base), and between frond leaf area and number of leaflets, were determined by natural logarithmic regressions to estimate the total area of each frond. Palm total leaf area was then estimated by adding the area of the composing fronds. We fit 14 separate regression models that related one or more of the morphological variables (number of fronds, diameter at breast height, stem height) to the total leaf area. Our results show that palm total leaf area is directly proportional to the number of fronds and palm size as reflected in stem height and diameter. Eight out of the 14 models had r ² values of >0.90 and incorporated a diverse combination of predictor variables. Simple linear regression models were more congruent with the observed values of total leaf area, whereas natural logarithmic models overestimated the value of total leaf area for large palms. Both approaches show a high degree of association among morphological characters in E. oleracea supporting the hypothesis that palms behave like unitary organisms, and are morphologically constrained by the lack of secondary meristems. To afford attaining canopy heights, woody palms need to show a high degree of phenotypic integration, shaping their growth and allometric relationships to match spatial and temporal changes in resources.     

Comparison of seedling recruitment under arborescent palms in two Neotropical forests

Certain overlying strata in forests may disproportionately reduce seedling density and species richness. For eight arborescent palm species, we quantified the relative restriction of seedling recruitment under individual palms versus non-palm sites and extended to the landscape scale by quantifying the total area covered by arborescent palms at Barro Colorado Island (BCI), Panama and La Selva Biological Station, Costa Rica. We also examined whether differences among palm species in restricting seedling recruitment were associated with differences in crown architecture, litter depth, and light availability. Woody seedlings had lower mean density/m² and mean number of species/m² under individual palms than at non-palm sites for all four palm species at BCI, but for none at La Selva. Estimated species richness for woody seedlings, derived via rarefaction, was lower under palm than non-palm microsites at both BCI and La Selva, but not for non-woody seedlings. Differences in seedling density corresponded to some key architectural characters that differed among the palm species. Light availability was lower under palm than non-palm microsites at both BCI and La Selva, but only estimated species richness of woody seedlings at BCI was strongly correlated with % canopy openness. The coverage of arborescent palms was much lower at BCI than La Selva. Therefore, at BCI, the relative restriction of woody seedling recruitment under individual palms does not accumulate greatly at the landscape scale. At La Selva, for woody seedlings, only estimated species richness was relatively limited under palms, and non-woody seedlings had relatively lower mean density/m² and mean number of species/m² under only one palm species. Therefore, the relative restriction of seedling recruitment by arborescent palms at La Selva is limited at both individual and landscape scales.     

Detection and differentiation of African coconut phytoplasmas: RFLP analysis of PCR-amplified 16S rDNA and DNA hybridisation

Phytoplasmas associated with lethal decline diseases of the coconut palm (Cocos nucifera) in west and east Africa were detected by the specific amplification of their 16S rRNA genes. The primers used were based on conserved mollicute-specific and coconut-phytoplasma 16S rRNA gene sequences. Phytoplasma 16S rDNA was amplified from all African decline affected palms, some periwinkle maintained phytoplasmas, but not from healthy palms, infected palms from Florida or from the Cocos spiroplasma and Acholeplasma sp. mollicutes. African phytoplasmas were also detected by DNA hybridisation using two probes from the palm lethal yellowing phytoplasma from Florida. Probes hybridised at moderate stringency to dot blots of lethal decline affected palms from Africa, indicating possible genetic relationships between different coconut phytoplasmas. RFLP analysis of rDNA fragments (length c. 1.45 kbp) detected polymorphisms, indicating that the pathogens found in west and east Africa are not identical. This provides a useful tool for further epidemiological studies of African coconut phytoplasmal diseases.     

Chemical ecology of Cyclocephala forsteri (Melolonthidae), a threat to macauba oil palm cultivars (Acrocomia aculeata,Arecaceae)

The environmental unsustainability of African oil palm crops is a growing worldwide concern, and the macauba palm in tropical Southern America surges as the most viable substitute for the production of first-generation biodiesel as a renewable fuel. Large-scale cultivation of the macauba palm, however, is bound to suffer a major setback due to the fast emergence of a florivorous pest threat, Cyclocephala forsteri, a scarab beetle species that can severely reduce fruit yield. Like other congenerics, female and male C. forsteri are night-foraging and driven in large numbers to macauba palm inflorescences by specific volatile organic compounds. In the present study, we assessed the kairomonal cues involved in this plant–florivore interaction and their potential application in selective pest management strategies. Headspace samples of the floral fragrance of macauba palms at our study site in Central Brazil were largely dominated by 4-methylanisole (>97% relative amount), which along with the minor constituents 2-isopropyl-3-methoxypyrazine and 2-sec-butyl-3-methoxypyrazine triggered electroantennographic responses from both female and male C. forsteri. Field behavioural assays evidenced that beetles of this species were exclusively attracted to scented traps baited with 4-methylanisole. Increased total scent discharge attained with an ultrasonic piezoelectric diffuser has positively influenced attractiveness efficiency of the trapping setup. 4-Methylanisole is hereby identified as yet another volatile kairomone involved in highly selective attraction of potential pest florivorous cyclocephaline scarabs associated with economically exploitable palms and should be viewed as a key element in short-term integrated management plans for the cultivation of the macauba palm in South America.