Myrica Faya Research Articles

Oviposition of the invasive two-spotted leafhopper on an endemic tree: Effects of an alien weed, foliar pubescence, and habitat humidity

The two-spotted leafhopper, Sophonia rufofascia (Kuoh and Kuoh), is an exotic pest from South-East Asia that attacks a wide variety of plant species in Hawaii. Myrica faya Aiton is an aggressive exotic weed that displaces and excludes native plants in Hawaiian forests. It has been argued that because of the high nutritional quality of its foliage, M. faya might facilitate leafhopper invasion of native Hawaiian ecosystems that were originally dominated by the endemic tree Metrosideros polymorpha (Gaudichaud). In the present study, we quantified suitability of M. faya and M. polymorpha as ovipositional hosts for S. rufofascia. Overall, leafhoppers preferred to deposit their eggs into the foliage of M. faya. M. faya presence in the area did not affect leafhopper oviposition on M. polymorpha. Foliar pubescence provided good protection of hirsute morphotypes of M. polymorpha. At the same time, glabrous M. polymorpha morphotypes were quite suitable for leafhopper oviposition. There was no difference in the abundance of leafhopper eggs along a precipitation gradient. Our results confirm that invasion of native Hawaiian forests by the weed M. faya will facilitate their invasion by S. rufofascia. Because of the broad host range characteristic of the two-spotted leafhopper, this build-up may adversely affect a number of endemic plant species growing in native forests.

Host Specificity of Epiphytic Bryophyte Communities of a Laurel Forest on Tenerife (Canary Islands, Spain)

Abstract We studied bryophyte species composition on five tree species (Erica scoparia, Laurus azorica, Myrica faya, Ilex canariensis, and I. Perado) of the laurel forest on Tenerife in order to determine the dominant factors influencing bryophyte community structure. Most of the 37 bryophyte species we found (24 liverworts and 11 mosses) are facultative epiphytes; many were found on several tree species, while five occurred on all tree species. DCA and CCA indicated that bryophyte species composition is significantly related to tree species identity. For each tree species, bark characteristics, plot exposure (windward and leeward to the prevailing trade winds), height (50 or 130 cm), tree size, and uprightness have differing relationships to bryophyte species composition. Bryophyte growth forms appeared to relate to the moisture conditions of the tree bark.

Spatial patterns of trees and juveniles in a laurel forest of Tenerife, Canary Islands

Spatial patterns are important characteristics of the forest and theycan reveal such things as successional status and ecological characteristics ofthe species. We tested the hypothesis that spatial distribution will bedifferent, depending on whether the species is intolerant or tolerant to shade.We assessed the spatial distribution of trees (> 4 cm dbh) andjuveniles in eight laurel forest plots. A univariate spatial analysis(performed with Ripley's K1) showed that all tree species havesignificantaggregation at short distances (2 m). Nevertheless, two groups ofspecies could be differentiated: Erica scoparia,Myrica faya and Ilex canariensisshowed a tendency for aggregation at large distances (larger than 6m)while L. azorica and Prunuslusitanicashowed aggregation only at shorter distances. Ripley's BivariateK1,2 analyses showed no significant differences in the spatialdistribution ofanalyzed species pairs from a null model. Only Laurusazoricahad a sufficient sample size for analysis of juvenile distribution. Aunivariateanalysis revealed thatL. azorica seedlings (stems 50 cm high and < 4 cm dbh)didnot show strong clumping even at short distances. L.azoricasaplings had no significant aggregation with, nor repulsionfrom, adults of the same or different species. Spatial patterns of the speciesshould be considered in the development of restoration plans of the laurelforest 90%of which has disappeared or been intensively disturbed on Tenerife Island.

Leaf Gas Exchange Characteristics in Relation to Leaf Canopy Position of Myrica faya in its Native Environment (Tenerife, Canary Islands)

Abstract: Diurnal courses of gas exchange were measured throughout one year in fully expanded current‐year leaves in the uppermost canopy (sun leaves, 18 m above ground) and in the lower canopy (shade leaves, 12 m above ground) of Myrica faya Ait., a dominant component of the Canarian laurel forest in Tenerife, Canary Islands, Spain. M. faya showed large differences between sun and shade leaves in gas exchange characteristics (about 50 % of maximum carbon assimilation rate (Amax) reduction in shade leaves, but this reduction can be higher on specific days) that were modulated by strong light attenuation and high leaf area index (LAI) of the stand. This species presented low Amax, about 10 μmol m‐2 s‐1, high maximum transpiration (E, 8 mmol m‐2 s‐1) and stomatal conductance (gs, 750 mmol m‐2 s‐1) and very low instantaneous water use efficiency (WUE, mean maximum 1.1 mmol mol‐1) and A/gs (mean maximum 23.5 μmol mol‐1). M. faya responded to high air vapour pressure deficit (VPD), decreasing its gs but maintaining relatively high values of A and E during the studied period. Stomatal response to VPD showed a higher sensitivity than its congeners, M. cerifera, and Laurus azorica, tree species co‐occurring in the Canarian laurel forest. In general, all these gas exchange characteristics lead us to consider this species more similar to subtropical plants of humid regions than to species of the Mediterranean region.

Distribution and Abundance of Mymarid Parasitoids (Hymenoptera: Mymaridae) of Sophonia rufofascia Kuoh and Kuoh (Homoptera: Cicadellidae) in Hawaii

Abstract The abundance of mymarid parasitoids attacking the two-spotted leafhopper (Sophonia rufofascia [Kuoh and Kuoh]), a polyphagous pest recently adventive to Hawaii, was monitored using yellow sticky cards deployed in several areas on the islands of Kauai and Hawaii. The yellow cards captured Chaetomymar sp. nr bagicha Narayanan, Subba Rao, & Kaur and Schizophragma bicolor (Dozier), both adventive species, and Polynema sp. Haliday, which is endemic to Hawaii (Hymenoptera: Mymaridae). The former two species were most abundant at all sites. On Kauai, there was a negative correlation between the captures of C. sp. nr bagicha and those of Polynema sp. Throughout the season, the increase in parasitoid numbers generally followed the increase in leafhopper numbers. C. sp. nr. bagicha and S. bicolor showed distinct habitat preferences. Removal of Myrica faya Aiton, an invasive weed that is a highly preferred two-spotted leafhopper host, decreased the overall numbers of captured parasitoids, but led to a twofold increase in the ratio of trapped parasitoids/hosts in weed-free areas.

DIET OF THE ENDEMIC MADEIRA LAUREL PIGEON AND FRUIT RESOURCE AVAILABILITY: A STUDY USING MICROHISTOLOGICAL ANALYSES

Abstract We studied the temporal diet variation of the endemic Madeira Laurel Pigeon (Columba trocaz) and fruit resource availability in the laurel forests of northwestern Madeira Island, during 1996 and 1997. We studied a total of 224 fecal samples using microhistological methods and conducted surveys of fruiting phenology throughout a year. Fruits (pulp and seeds) represented 57% of the optical fields analyzed. Leaves and flowers constituted 38% and <1% respectively. Over 33 plant species were identified in the fecal samples. Fruits of Ocotea foetens, Laurus azorica, Persea indica, and Ilex canariensis (fruits and leaves) were the most frequently detected food items. Most seeds were defecated intact (Ilex canariensis, Myrica faya, Visnea mocanera, Ocotea foetens, and Apollonias barbujana), except in the case of Laurus azorica where most were damaged. The diet showed a marked seasonal variation. Fruits constituted the major component of the diet in winter and autumn, whereas leaves were frequent in sprin...

The influence of an invasive tree species ( Myrica faya) on the abundance of an alien insect ( Sophonia rufofascia) in Hawai'i Volcanoes National Park

Following its accidental introduction into Hawai'i in 1987, Sophonia rufofascia Kuoh and Kuoh (Homoptera: Cicadellidae) has become a concern due to the wide range of plant damage that can result from its feeding and ovipositing. Sophonia rufofascia abundance was monitored on the invasive non-native Myrica faya Aiton tree, the dominant native Hawaiian tree Metrosideros polymorpha Gaudich-Beaupre, and on two common native shrubs in paired areas within Hawai'i Volcanoes National Park. These areas included Special Ecological Areas (SEAs) — where Myrica faya had been mechanically removed, and in immediately adjacent control areas — where Myrica faya was still present. Sophonia rufofascia abundance was five times greater on Myrica faya than on co-occurring Metrosideros polymorpha in control areas. In addition, the abundance of S. rufofascia on native plants was between two and 19 times greater in areas where Myrica faya was present, than in those areas where the tree had been mechanically removed. These results indicate that Myrica faya promotes a localized increase in S. rufofascia abundance.

Egg Parasitoids of Sophonia rufofascia (Homoptera: Cicadellidae) in Hawaii Volcanoes National Park

Abstract Parasitism of the leafhopper Sophonia rufofascia (Kuoh and Kuoh), a recent immigrant that has become a widespread pest in Hawaii, was examined in a 1-year survey in Hawaii Volcanoes National Park. Samples of young leaves of four plant species infested with eggs of S. rufofascia were collected at five sites ranging from 880 to 1190 m in elevation. Leafhopper eggs were parasitized principally by three species of Mymaridae (Hymenoptera): Polynema sp., Schizophragma sp. probably bicolor (Dozier), and Chaetomymar sp. Although parasitism by each species fluctuated at levels usually below 10%, all three were detected consistently across most host plants, sites, and sample periods. Total parasitism differed at a marginally significant level among host plants and sites, but not among sample periods. Total parasitism averaged 14.3% (maximum: 26.3%) on Dodonaea viscosa Jacquin, 10.6% (maximum: 17.5%) on Myrica faya Aiton, 8.7% (maximum: 29.5%) on Metrosideros polymorpha Gaudich-Beaupre, and 1.6% (maximum: 4.3%) on Vaccinium reticulatum Smith. Parasitism was generally higher at sites lower in elevation. Further monitoring is recommended to determine whether parasitism will increase to levels that can effectively suppress S. rufofascia populations. The efficacy of natural enemies already present in Hawaii is important because concern over nontarget impacts on endemic leafhoppers makes introduction of new biological control agents difficult.

Exotic Grasses Potentially Slow Invasion of an N-fixing Tree into a Hawaiian Woodland

This paper examines the effect of an abundant non-native species, Schizachyrium condensatum, on establishment of a later arriving, but very potent invader, Myrica faya, in a seasonally dry forest on the island of Hawaii. Using a replicated removal experiment, we determined that S. condensatum, a perennial C4 grass, reduced recruitment of M. faya, an N-fixing tree species. Recruitment of Myrica was 90% higher in S. condensatum removal plots compared to controls. We believe that because S. condensatum substantially reduces light at the soil surface it reduces germination and early seedling growth of the M. faya.

The significance of xanthophylls and tocopherols in photo-oxidative stress and photoprotection of three Canarian laurel forest tree species on a high radiation day

Chloroplast pigments, chlorophyll fluorescence, and tocopherols in sun leaves of the Canarian laurel forest species Myrica faya, Laurus azorica, and Persea indica were characterized during the diurnal course of a high irradiation summer day. All species showed a de-epoxidation of the xanthophyll cycle and a decline of the photochemical efficiency of photosystem II measured as the Fv/Fm fluorescence ratio. Whereas in M. faya, decline and recovery of Fv/Fm was only correlated to zeaxanthin formation, these relations were divergent in L. azorica and P. indica . In P. indica, Fv/Fm did not fully recover until the next morning. Apparently, the decrease of Fv/Fm during the day reflected only a zeaxanthin-dependent, quickly recovering component in M. faya, but an additional component, probably due to photodamage processes requiring repair activities, was observed in L. azorica and P. indica . In leaves of those two species, α-tocopherol concentrations varied during the diurnal course, probably indicating active oxygen scavenging action. In P. indica leaves, a degradation and restoration of chlorophyll contents were observed during the day. The conclusion is that M. faya is most resistent to high light stress and P. indica most sensitive, which coincides with known ecological traits of these species.

Radial variation in sap flow in five laurel forest tree species in Tenerife, Canary Islands.

Variations in radial patterns of xylem water content and sap flow rate were measured in five laurel forest tree species (Laurus azorica (Seub.) Franco, Persea indica (L.) Spreng., Myrica faya Ait., Erica arborea L. and Ilex perado Ait. ssp. platyphylla (Webb & Berth.) Tutin) growing in an experimental plot at Agua García, Tenerife, Canary Islands. Measurements were performed around midday during warm and sunny days by the heat field deformation method. In all species, water content was almost constant (around 35% by volume) over the whole xylem cross-sectional area. There were no differences in wood color over the whole cross-sectional area of the stem in most species with the exception of E. arborea, whose wood became darker in the inner layers. Radial patterns of sap flow were highly variable and did not show clear relationships with tree diameter or species. Sap flow occurred over the whole xylem cross-sectional area in some species, whereas it was limited to the outer xylem layers in others. Sap flow rate was either similar along the xylem radius or exhibited a peak in the outer part of the xylem area. Low sap flow rates with little variation in radial pattern were typical for shaded suppressed trees, whereas dominant trees exhibited high sap flow rates with a peak in the radial pattern. Stem damage resulted in a significant decrease in sap flow rate in the outer xylem layers. The outer xylem is more important for whole tree water supply than the inner xylem because of its larger size. We conclude that measurement of radial flow pattern provides a reliable method of integrating sap flow from individual measuring points to the whole tree.

Seed bank analysis of tree species in two stands of the Tenerife laurel forest (Canary Islands)

We analyzed the germination from the seed bank for two laurel forest stands (Moquinal versus Aguirre) of Tenerife collected at two different seasons (summer versus winter). We incubated and monitored germination in greenhouse conditions for 1 year. A high variability in germination was found between trays. Germination was much higher in summer than in winter, especially from Moquinal seed bank. Shade tolerant species ( Laurus azorica, Persea indica, Rhamnus glandulosa and Viburnum tinus) have a shorter germination delay than shade-intolerant species ( Erica arborea, Erica scoparia and Myrica faya), which dominate the seed bank. The species composition of germinating seeds after one year did not reveal any differences between sites nor between, despite the high differences in number between seasons. We compared the species composition of germinating seeds to that of the canopy (expressed as basal area). The results indicate that the winter seed bank does not significantly differ from the canopy composition in the Aguirre stand. We interpret our results to imply that the Aguirre stand is of an earlier successional stage than the Moquinal stand, because of a higher species richness in the germinated tree seeds, and compositional similarities between the winter seed bank and the canopy (both characteristic of earlier successional stages).

Feeding Damage of the Introduced Leafhopper &lt;I&gt;Sophonia rufofascia&lt;/I&gt; (Homoptera: Cicadellidae) to Plants in Forests and Watersheds of the Hawaiian Islands

Experiments were performed to determine the role of the leafhopper Sophonia rufofascia (Kuoh & Kuoh) in damage observed on forest and watershed plants in the Hawaiian Islands. Laboratory manipulation of leafhopper populations on fiddlewood, Citharexylum spinosum L., caused interveinal chlorosis and vein browning on young fully expanded leaves similar to that observed on leafhopper infested plants seen in the field and necrosis on older leaves. Field studies with caged “uluhe” fern, Dicranopteris linearis (Burman), demonstrated that frond veins turned brown within 2 d of leafhopper feeding; and by 141 d after feeding, an average of 85% of the surface area of the fronds were necrotic compared with only 12% necrosis in untreated cages. Field trials with stump-cut firetree, Myrica faya Aiton, were performed to determine the effect of leafhopper feeding on new growth. Our studies showed that the new growth in exclusion cages had significantly greater stem length and diameter, a higher number of nodes, fewer damaged leaves, and almost twice as much leaf area compared with plants caged but with the sides left open to permit leafhopper access. Microscopic examination of sections through damaged areas of several leafhopper host plants showed vascular bundle abnormalities similar to those associated with hopperburn caused by potato leafhopper, Empoasca fabae (Harris), feeding on alfalfa. On Hawaiian tree fern, Cibotium splendens (Gaudichaud), oviposition into the midvein also disrupted vascular bundle integrity and often caused death of the distal portions of the pinnule.

Tree regeneration and future dynamics of the laurel forest on Tenerife, Canary Islands

Abstract. We studied two sites in the laurel forest of Tenerife to predict future changes in canopy composition. We used two projection methods: Horn's ‘Markovian Projection’, which utilizes information on juveniles in the vicinity of canopy trees, and a 'Stand Projection’, which ignores such information. We performed these projections both including and excluding a‐sexual regeneration. Although all of our projections predict a change in species composition, inclusion of a‐sexual reproduction decreased the magnitude of successional change. The persistence of Prunus lusitanica and Ilex canariensis appears to be highly dependent on a‐sexual regeneration.Both the Markov‐ and stand projections predict a slight convergence in species composition between the two sites when only sexual regeneration is considered, and also a higher dominance of the shade‐tolerant species Laurus azorica. When a‐sexual regeneration is also considered, some divergence is shown, with less projected change in the stand projection than in the Markov projection. In spite of some differences between the models, general patterns such as an increase of shade‐tolerant species (Laurus azorica and Prunus lusitanica) and a decrease of shade‐intolerant species (Erica arborea, Erica scoparia and Myrica faya) are consistent.

Seed dispersal by common ravens Corvus corax among island habitats (Canarian Archipelago)

The role of the common raven (Corvus corax; Corvidae) as a seed dispersal agent for plants in the Canary Islands was studied by analysing 2672 pellets collected from all islands of the archipelago. Seeds of 16 species of phanerogams were found (four endemic to the Canaries, three endemic to the Macaronesian islands, six not endemic, and three introduced by man). Vegetation in this archipelago is highly structured according to altitude creating different types of macrohabitats. The quality of the transport of seeds between habitats was evaluated in a preliminary way by making use of the very high fidelity of the plant species to particular macrohabitats. Of the 102 580 potentially fertile seeds (excepting the other 51 061 infertile Ficus carica seeds) transported by common ravens, 76.5% were regurgitated in theoretically suitable habitat while the remaining 23.5% were taken to habitats that were not appropriate for the establishment. Common ravens improved germination of six species, whereas an opposite effect was observed for three others. The percentage of viable seeds did not differ for any species between pellet seeds and seeds collected directly from the plants. Considering results from germination and viability experiments and macrohabitat patterns of dispersal, the common raven seems to be an important disperser for nine plant species: Lycium intricatum (Solanaceae), Opuntia ficus-indica (Cactaceae), Rubia fruticosa and Plocama pendula (Rubiaceae), Juniperus turbinata and J. cedrus (Cupressaceae), Phoenix canariensis (Arecaceae), Asparagus pastorianus (Liliaceae), and Myrica faya (Myricaceae).

Regeneration strategies of tree species in the laurel forest of Tenerife (The Canary Islands)

The laurel-forest of the Canary Islands is a montane cloud-forest. In order to gain some knowledge on the processes that maintain tree species diversity, we conducted an analysis of three different laurel-forest plots of the Anaga massif (Tenerife), varying in canopy composition but growing under similar environmental conditions. For each plot we recorded basal area of the canopy trees (h 1.30 m), as well as seed-bank composition. The plots have similar regeneration composition, which appears to be independent of differences in canopy composition. Laurus azorica is the most common seedling species, whereas Prunus lusitanica is the most abundant species among suckers and basal shoots. Neither Erica arborea nor Myrica faya, the two main canopy trees in one of the plots, were found in any of the stands as seedlings or suckers, despite their existence as viable seeds in the seed-bank. The regeneration composition and the canopy composition in one of the plots is remarkable different, revealing differents dynamics processes in the three plots. The results suggest the existence of three well-defined ecological groups: pioneer (regeneration primarily by seedlings), non-pioneer (regeneration by seedlings and suckers) and remnant species (regeneration primarily by suckers).These three groups and the effect of small scale disturbances (natural and human-induced), could help to understand the maintenance of tree species richness.

Reducing the Risks of Nonindigenous Species Introductions

A though plants and animals have always spread across the globe, expanding their ranges and invading new territories, human civilization has accelerated these biological invasions to an extraordinary degree. Nonindigenous species represent a major threat to the integrity of natural systems, because they can alter nutrient regimes, develop into monocultures, and drive native species to extinction (e.g., the nitrogen-fixing tree Myrica faya [Vitousek and Walker 1989], the zebra mussel Dreissena polymorpha [Mills et al. 1994, Roberts 1990], the purple loosestrife Lythrum salicaria [Mercer 1990], and the brown tree snake Boiga irregularis [Burdick 1994]). Although the US government recognizes the risks posed by nonindigenous species and for nearly a century has had legislation in place aimed at reducing harm-

An Invader Alters Germination and Growth of Native Dominant Tree in Hawai'i

Myrica faya, an introduced nitrogen—fixing tree, is rapidly invading volcanically disturbed forests in Hawaii Volcanoes National Park on the island of Hawai'i. We investigated the direct effects of Myrica on the establishment and growth of the native tree, Metrosideros polymorpha, in a forest that is recovering from burial under a 10—200 cm deep layer of volcanic cinder. The number of Metrosideros seedlings found under Metrosideros trees, in the open, and under Myrica trees was 0.12/m2, and 0.01/m2, and zero, respectively. Myrica litter inhibited Metrosideros germination in field experiments; germination occurred only when Myrica litter was removed. In open sites, the addition of nitrogen—rich Myrica soils increased dry mass accumulation of transplanted Metrosideros seedlings. Shade from Myrica canopies (or shade cloth) increased survivorship and height growth but not dry mass accumulation of Metrosideros seedlings. Isolated Metrosideros trees increased diameter growth in response to nitrogen fertilizer but not in response to the presence of adjacent Myrica trees, despite previous findings that Myrica trees elevate available nitrogen in the soil. Myrica basal diameter and height growth were consistently greater than that of Metrosideros in all size classes. Although Myrica does not readily invade closed, late—successional Metrosideros forests, on young, volcanically disturbed soils it is rapidly establishing dense, monospecific stands under which Metrosideros does not regenerate.

The Self‐Thinning Rule: Dead or Unsupported?‐‐A Reply to Lonsdale

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Plant-soil interactions in primary succession at Hawaii Volcanoes National Park.

Plant nutrient status and physiological processes were examined in relation to soil nutrient characteristics under individuals of five species colonizing a young cinder deposit in Hawaii Volcanoes National Park. Two exotic species, Buddeleja asiatica and Myrica faya, had high photosynthetic rates and high nitrogen concentrations and relatively easily decomposed leaves; soils under them had high concentrations of nitrogen, cations, and organic matter and high rates of net nitrogen mineralization. At the other extreme, the natives Metrosideros polymorpha and Vaccinium reticulatum had low plant concentrations and photosynthetic rates, and low concentrations and turnover rates of N in the soil. Thus, a strong correlation exists between soil processes and plant processes, suggesting a positive feedback cycle.