Preliminary evidence suggests that beech scale insect honeydew has a negative effect on terrestrial litter decomposition rates in

Honeydew production by New Zealand beech scale insects (Ultracoelostoma spp., Hemiptera: Margarodidae) is widely considered to have a positive influence on native animal abundance and ecosystem functioning. As a first assessment of whether there is a positive relationship between honeydew throughfall and litter decomposition rates, we placed experimental litter bags in each of 10 high and 10 low honeydew plots in mixed southern beech (Nothofagus) forest at each of two sites, Lakehead and Rotoiti, in the Nelson Lakes National Park. High and low honeydew plots were selected using sooty mould biomass on the forest floor as a surrogate for honeydew throughfall, as sooty mould biomass was shown to be strongly correlated (r = 0.906) with scale insect population size at the Rotoiti site. Contrary to our expectation, terrestrial litter decomposition was significantly lower in high honeydew plots than in low honeydew plots, at both Lakehead and Rotoiti. The presence of introduced wasps (Vespula spp., Hymenoptera: Vespidae) at the Lakehead site did not appear to have any significant effect on litter decomposition rates, despite the fact that wasps are thought to intercept much of the honeydew produced in this forest. Variance in litter decomposition rates between high and low honeydew treatments was predominantly determined by a direct relationship between sooty mould biomass and litter decomposition rate at the scale of individual litter bags. However, the mechanistic explanation for the observed relationship is unclear. Future studies should be directed towards quantifying the functional relationship between honeydew throughfall and growth rates of sooty mould, and their subsequent effects on abiotic conditions, microarthropod community dynamics and microbial activity rates in litter.     

Invasive wasps,not birds,dominate in a temperate honeydew system

The Avian Convergence Hypothesis states that avian–honeydew associations are likely to develop when biogeographic and/or climatic factors limit the formation of ant–honeydew associations (the dominant association in tropical ecosystems). In this study we examine a honeydew‐influenced forest system in an island archipelago where ant diversity is low but invasive Vespula wasp species (Vespidae) are present. We found honeydew production was highly seasonal, with both standing crop and 24‐h production peaking in summer. When Vespula wasps were abundant (summer and autumn) they preferentially visited infested trees and fed regularly on honeydew droplets on infested branches. Two ant species occasionally fed on honeydew. No other insects or birds were observed feeding on honeydew during the study period. With the exception of Vespula, honeydew does not appear to be a preferred food source in this community, possibly because of the range of other food resources available in surrounding forest, farmland and gardens. The abundance of Vespula wasps at the site may also have disrupted bird–honeydew associations. We suggest the Avian Convergence Hypothesis could be restated to explicitly include both nectar availability and invasive social insects as both are likely to influence bird use of honeydew.     

A diverse assemblage of moths feeding on aphid honeydew

Adult butterflies and moths (Lepidoptera) use their proboscises to feed on flower nectar and other types of liquid food. Aphids frequently secrete honeydew from their anuses, attracting various types of insects, such as ants. Adult lepidopterans are also known to feed on aphid honeydew. However, very few studies have clarified the species composition and morphology of moths feeding on aphid honeydew. In late June 2017, we found nocturnal moths sipping honeydew secreted by Shivaphis celti and Sitobion cornifoliae (Hemiptera: Aphididae) on leaves of Celtis sinensis (Cannabaceae) and Cornus kousa (Cornaceae), respectively, at the edge of a secondary forest in central Japan. The moths were observed to uncoil their proboscises and feed on honeydew on the leaves. No moths were observed to feed on honeydew directly from aphids. Nocturnal moths of 60 species (11 families) and 16 species (7 families) were collected from honeydew on Ce. sinensis and Co. kousa leaves, respectively. Eleven moth species were shared between the two types of honeydew. The most abundant species, Oncocera semirubella (Lepidoptera: Pyralidae), accounted for 44.7% of all individuals. The sex ratio of O. semirubella was female biased. Of the 65 moth species collected on aphid honeydew, 52.3% (34 species) have been previously reported to visit flowers. Moths visiting honeydew had relatively short proboscises and small body size. These results suggest that aphid honeydew is an important, accessible food resource for moths of small size.     

Revising the convergence hypothesis of avian use of honeydew: evidence from Dominican subtropical dry forest

A honeydew-producing scale insect (family Margarodidae, tribe Xylococcini, genus Stigmacoccus ) was found associated with the tree Bursera simaruba in subtropical dry forests at elevations of 100–400 m on the south side of the Sierra de Bahoruco, Pedernales Province, Dominican Republic. At two study sites, 91% of Bursera trees supported locally dense populations of Margarodidae. Fifteen species of birds were observed foraging on the honeydew, but most observations were of the winter resident Cape May warbler ( Dendroica tigrina ) and black-throated blue warbler ( D. caerulescens ), and the permanent resident bananaquit ( Coereba flaveola ) and black-crowned palm tanager ( Phaenicophilus palmarum ). The Cape May warbler actively defended the honeydew resource but frequency of use of honeydew was influenced by the close presence of flowering agave and scale insect density. Data suggest that honeydew may be a critical component of the diet of this species especially during the late winter dry-season. Hymenopteran insects also were observed feeding on honeydew, but rates of consumption did not approach that of avian species. The occurrence of this phenomenon in Dominican dry forest is discussed in light of the convergence hypothesis of bird use and defense of homopteran honeydew in which it is proposed that birds are able to maintain relationships with scale insects in moist, warm temperate forests because it is in these climates where ant abundance is low. We suggest that our observation of a well-developed bird–homopteran system in classic subtropical dry forest supports the proposed mechanism of reduced competition with ants allowing bird use of honeydew, but we suggest that a broader array of especially insular habitats which may be relatively depauperate in terms of ants also can be expected to support bird–homopteran systems.     

Soluble carbon production by honeydew scale insects in a New Zealand beech forest

We estimated the annual production of honeydew per unit land area of beech (Nothofagus spp.) forest by measuring the amount of honeydew produced in 24 h by scale insects (Ultracoelostoma spp.) (Hemiptera: Margarodidae) every month for 2 years. We used exclosures to prevent animals (notably Vespula wasps) removing honeydew, and we compared the standing crop of honeydew inside permanently closed exclosures with that outside exclosures. Honeydew production and the number of honeydew droplets was highly variable between individual trees, tree type, position on tree, and, exclosure type, and within and between years. The amount of honeydew available outside exclosures was significantly reduced in year 2, predominantly by Vespula wasps, even though wasp density was relatively low. Sugar composition also varied between tree type and between years. Up to 5% of the sugar was glucose, with varying proportions of fructose, sucrose and oligosaccharides. The surface area of trees infested with scale insects was estimated using allometric regression relationships between tree diameter and total surface area of tree trunk and branch material. These estimates were combined with measurements of tree diameter in 10-m radius circular plots to give a production estimate of between 3500 and 4500 kg dry weight honeydew ha^-1 year^-1. Using this data, combined with previously published estimates of carbon uptake, it was estimated that between 6 and 8% of net primary productivity was released as honeydew. Honeydew scale insects provide large amounts of biologically available carbon in the form of soluble sugar. It is a crucial resource for the above-ground system, and probably also for the below-ground system. We conclude that scale insects have the potential to function as keystone species in these forests.     

Forest community analysis and the point-centered quarter method

The point-centered-quarter (PCQ) method has been applied in community analysis since the publication of the method nearly 50 years ago. This and other distance methods offer increased sampling efficiency over fixed-area plots (FAP), but have long been known to produce biased density estimates when plant distribution deviates from random spatial patterns. Spatial indices have been developed to quantify the direction of this bias when plant distributions are aggregated or evenly distributed. Its continued use, especially in community analysis, requires additional scrutiny in measurements of community structure. We measured 14 forest stands of varying age, elevation and disturbance regime using FAP and PCQ methods. Density estimates were biased, with the point-centered quarter method lower than fixed-area plot estimates when stems were aggregated and higher when stems were evenly spaced. In general the PCQ method underestimated species richness. The efficiency of the PCQ method makes it popular for ordination studies, although comparison of community structure varied from 18% to 90% similarity between the measurements of species basal area in the same stands using the two different methods. The bias observed in calculations of stem density, species abundance and community similarity indicate that use of the PCQ method should be approached with caution when used in community level analysis.     

Determining the impact of scale insect honeydew, and invasive wasps and rodents, on the decomposer subsystem in a New Zealand beech forest

Relatively few studies have considered how aboveground invasive consumers influence decomposer communities. We investigated the potential effects of three types of animals on the decomposer subsystem in a floristically simple New Zealand Nothofagus forest. These animals are the native beech honeydew scale insect (Ultracoelostoma spp.) that secretes large amounts of sugar-rich honeydew that washes to the soil, invasive social wasps (Vespula spp.) that remove honeydew and prevent it from reaching the ground, and invasive rodents (the house mouse (Mus musculus) and ship rat (Rattus rattus)) that are predators of litter invertebrates. We performed a 4 years manipulative experiment involving addition of synthetic honeydew to the soil surface at amounts equal to that washed to the soil both in the absence and presence of wasps. All treatments were subjected to both exclusion and non-exclusion of rodents. Full honeydew addition influenced several components of the belowground community (both positively and negatively), and promoted fungi and fungal feeding fauna at the expense of bacteria and bacterial-feeders. The reduced addition of honeydew (representing effects of wasps) reversed some (but not all) effects of full honeydew addition. Rodents also influenced some belowground organisms, often reversing the effects of honeydew addition. The honeydew levels simulating wasp effects and the presence of rodents both greatly promoted humus carbon and nutrient storage relative to all other treatments, highlighting that invaders can alter soil carbon sequestration and nutrient capital. Our study points to invasive animals modifying the effects of a native animal on multiple components of the decomposer subsystem.     

The Hemiptera (Insecta) communities of tropical rain forest in Sulawesi

The structure and composition of Hemiptera communities of tropical rain forest in Dumoga-Bone National Park, Sulawesi, Indonesia were investigated over a 1-year period. The aim was to investigate the extent to which insect samples, obtained using six different techniques, were representative of the whole community, and to explore temporal and spatial variation in Hemiptera community composition. Sampling techniques employed were Rothamsted light trapping, canopy fogging, malaise trapping at both ground and canopy level, flight interception trapping and yellow water pan trapping. Overlap between faunas collected using different techniques was surprisingly low emphasizing the limitations of using any single method to sample and thereby describe the Hemiptera community. Differences were observed at the species, family and suborder levels. Similarly, there were major differences in faunal composition between sites and diversity appeared to peak at elevations between 600–1000 m. Seasonal changes were also significant but generally lower than between methods or sites. Results are discussed in relation to factors such as food availability and host specialization and the efficacy of each sampling method is reviewed in relation to the biology of the different Hemiptera groups and the composition of the samples obtained.     

Weather-Related Differences in Attractiveness of Protein Foods to

Low acceptance of protein baits by common (Vespula vulgaris) and German (V. germanica) wasps (Hymenoptera: Vespidae) occurred after rain in honeydew beech forest. This corresponded with a sharp decrease in the proportion of natural protein in the diet of V. vulgaris and V. germanica, and a reduction in the concentration of carbohydrate-rich honeydew in the crops of foraging wasps carrying liquid. The reduction of protein foraging most likely results from a change in the efficiency of foraging wasps at gathering high energy foods such as honeydew after rain, because rain reduces honeydew availability. Workers may therefore take longer to meet their own energy requirements before they can forage for protein to feed developing larvae.     

紫胶虫蜜露对地表蚂蚁多样性的影响

2009年12月至2010年5月,采用陷阱法在云南省墨江县雅邑乡调查了紫胶林地表蚂蚁群落多样性,分析了紫胶虫蜜露对地表蚂蚁多样性的影响.结果表明:紫胶虫蜜露资源的有无及变动对地表蚂蚁群落物种组成、多度及多样性均产生影响.在紫胶林样地共采集蚂蚁标本4953头,隶属5亚科23属34种,在对照样地共采集蚂蚁标本2416头,隶属5亚科20属30种;紫胶林地表蚂蚁相对多度、物种丰富度(S)及ACE估计值均高于对照样地,地表蚂蚁常见种和指示种均与对照样地不同,表明放养紫胶虫改变了地表蚂蚁群落结构;紫胶虫成虫期蜜露分泌量高于幼虫期,其地表蚂蚁相对多度、S及ACE估计值也高于幼虫期,且两阶段的蚂蚁常见种和指示种显著不同.     

Community structure and diversity of tropical forest mammals: data from a global camera trap network

Terrestrial mammals are a key component of tropical forest communities as indicators of ecosystem health and providers of important ecosystem services. However, there is little quantitative information about how they change with local, regional and global threats. In this paper, the first standardized pantropical forest terrestrial mammal community study, we examine several aspects of terrestrial mammal species and community diversity (species richness, species diversity, evenness, dominance, functional diversity and community structure) at seven sites around the globe using a single standardized camera trapping methodology approach. The sites-located in Uganda, Tanzania, Indonesia, Lao PDR, Suriname, Brazil and Costa Rica-are surrounded by different landscape configurations, from continuous forests to highly fragmented forests. We obtained more than 51 000 images and detected 105 species of mammals with a total sampling effort of 12 687 camera trap days. We find that mammal communities from highly fragmented sites have lower species richness, species diversity, functional diversity and higher dominance when compared with sites in partially fragmented and continuous forest. We emphasize the importance of standardized camera trapping approaches for obtaining baselines for monitoring forest mammal communities so as to adequately understand the effect of global, regional and local threats and appropriately inform conservation actions.     

Plant–rhizobia interactions alter aphid honeydew composition

Both above- and below-ground interspecific interactions contribute to ecosystem functioning in terrestrial systems, and the integration of below- and above-ground interactions is crucial for deepening our knowledge of nutrient cycling and community dynamics in terrestrial ecosystems. The present study explored the effects of plant–microbe interactions on aphid honeydew quality and quantity and important factors mediating ant–aphid mutualisms and below-ground nutrient dynamics. Soybean aphids (Aphis glycines) were inoculated onto two closely related strains of soybean plants: a nodulating strain that associates with rhizobia and a non-nodulating strain that does not harbor any nitrogen-fixing bacteria. As expected, prior to aphid inoculation, nodulating plants were significantly taller and had more leaves than non-nodulating plants. Aphids feeding on nodulating strains were found to reach slightly larger colony sizes and produce honeydew with significantly different sugar profiles than those feeding on non-nodulating plants. The honeydew collected from aphid colonies feeding on nodulating plants contained 160 % more total sugars than honeydew collected from colonies feeding on non-nodulating plants, but there was no difference in total amino acid-N content in honeydew from colonies feeding on the different plant strains. We discuss the implications of honeydew composition for nutrient cycling and community dynamics and suggest areas of future research to elucidate the consequences of altered aphid honeydew composition on ecosystem properties.     

The influence of habitat use and foraging on the replacement of one introduced wasp species by another in New Zealand

Abstract.

• 1 New Zealand was colonized by the German wasp, Vespula germanica (F.), in the 1940s and it subsequently became established throughout the country. The common wasp, V.vulgaris (L), colonized in the late 1970s and is still spreading.
• 2 The common wasp has replaced the German wasp in some habitats in New Zealand. Samples from a nationwide postal survey indicate that the common wasp is now the more abundant species in honeydew beech forests (Nothofagus spp.), and to a lesser extent in other native forests. The German wasp is still the more abundant wasp in rural areas (excluding forest). The two species are at present co-dominant in urban areas, although this may be a transient phase.
• 3 In honeydew beech forest the two species show different foraging patterns that provide the potential for local coexistence. Although both species are generalist feeders, the German wasp is more commonly found foraging for protein amongst the forest litter, whereas the common wasp forages more on shrubs and tree saplings. Despite this difference, the common wasp can still replace the German wasp in honeydew beech forest within a few years of invasion.
• 4 In honeydew beech forests in which the German wasp is the more abundant species it dominates honeydew trunks (sugar resource), whereas the common wasp dominates honeydew trunks in areas where it is the more abundant species. The change from German to common wasp domination of honeydew trunks is more rapid than the change in dominance in other microhabitats. Aggressive interactions may be taking place on this high quality, potentially defensible sugar resource.

     

Monitoring of the ground-dwelling beetle community and forest floor environment in 22 temperate forests across Japan

This data paper reports census data of ground-dwelling beetle and other fauna of the forest floor environment; collections were made from a network of 22 forest sites in Japan. To our knowledge, this represents the largest dataset for long-term monitoring of a ground-dwelling beetle community and other taxa in a ground environment in forests, which covers a broad climatic range in the temperate zone and is freely available. The network forms part of the Monitoring Sites 1000 Project launched by the Ministry of the Environment, Japan. It covers subalpine, cool- and warm-temperate and subtropical climatic zones and the four major forest types of Japan. Thirty-three permanent plots usually 1 ha in size were established in old-growth, secondary natural and a few plantation forests. Censuses of the ground-dwelling beetle community were conducted using pitfall trapping and forest floor environment monitoring every year from 2004 to the present. During the initial 9 years of the census (2004–2012), 59,762 beetle individuals (including 3182 larvae) of more than 314 species were recorded. This dataset includes taxonomy and biomass of each beetle individual and each taxonomic group of other invertebrates coincidently captured in pitfall trapping. The dataset also includes data related to ground coverage by forest floor vegetation, dry mass of the accumulated organic litter layer, and carbon and nitrogen contents and cellulose decomposition rate in organic layer and surface mineral soil. The data could be used to investigate geographical patterns and intra- and inter-annual dynamics of individual body mass, populations and community structures of ground-dwelling beetles, and their relationships with the forest floor environment. Furthermore, the data could be analyzed with other open datasets related to tree community dynamics and litter fall continuously measured in the same study plots. This dataset also provides information related to the distribution and average body mass of each beetle species.     

Microclimate and tree community linked to differences in lepidopteran larval communities between forest fragments and continuous forest

Aim  We aim to assess the impact of forest fragmentation on lepidopteran larval community and study the associations of microclimate and tree community with lepidopteran assemblage.
Location  Kibale National Park, Uganda.
Methods  We investigated the effects of forest fragmentation on leaf herbivory, density of lepidopteran caterpillars, species richness and diversity as well as the composition of herbivorous lepidopteran larval community. Microclimate, size of the fragment, distance to the continuous forest, and tree diversity were studied as possible explanatory factors. We sampled 10 Neoboutonia macrocalyx Pax. (Euphorbiaceae) trees in each fragment during dry and rainy season, total of four times, in a year to cover the seasonal variation.
Results  The rates of herbivory, total larval density and species richness were significantly lower in the forest fragments than in the continuous forest but species diversity expressed as Fisher's alpha did not differ. The dominance structure and community composition of the larval communities in the fragments was different from that of the continuous forest. None of the differences we observed were related to the fragment area or distance to the continuous forest. Instead, we found an indication of association between the herbivore and the tree communities. The fragments had significantly lower humidity during most of the day and higher temperature during the afternoons (14–17 h), which might partially explain the differences in lepidopteran larval communities.
Main conclusions  Decreased larval density and species richness as well as differences in the community composition and structure all highlight the importance of large continuous forest areas for maintaining larval biodiversity.     

Above-ground forest biomass is not consistently related to wood density in tropical forests

Aim  It is increasingly accepted that the mean wood density of trees within a forest is tightly coupled to above-ground forest biomass. It is unknown, however, if a positive relationship between forest biomass and mean community wood density is a general phenomenon across forests. Understanding spatial variation in biomass as a function of wood density both within and among forests is important for predicting changes in stored carbon in response to global change, and here we evaluated the generality of a positive biomass–wood density relationship within and among six tropical forests.
Location  Costa Rica, Panama, Puerto Rico and Ecuador.
Methods  Individual stem data, including diameter at breast height and spatial position, for six forest dynamics plots were merged with an extensive wood density database. Individual stem biomass values were calculated from these data using published statistical models. Total above ground biomass, total basal area and mean community wood density were also quantified across a range of subcommunity plot sizes within each forest.
Results  Among forests, biomass did not vary with mean community wood density. The relationship between subcommunity biomass and mean wood density within a forest varied from negative to null to positive depending on the size of subcommunities and forest identity. The direction of correlation was determined by the associated total basal area–mean wood density correlation, the slope of which increased strongly with whole forest mean wood density.
Main conclusions  There is no general relationship between forest biomass and wood density, and in some forests, stored carbon is highest where wood density is lowest. Our results suggest that declining wood density, due to global change, will result in decreased or increased stored carbon in forests with high or low mean wood density, respectively.     

南宁市几个功能区的植被群落结构特征分析

借助数量分析技术分析了广西南宁市植被结构特征。结果表明:(1)主要的绿化乔木有45种,灌木24种。这些植物基本上代表了南宁市绿化植物的主体,但在生物量比重等方面,还是少数种类占主要优势,亟待调整。(2)绿地植被群落的平均胸径与密度成极显著负相关,显示城市植被与自然植被的相似性,而总冠幅盖度与总密度和综合重要值之间成极显著正相关,则显示了城市人工植被的特殊性;(3)绿地面积与胸径成显著正相关,而与密度、冠幅盖度成极显著与近显著的负相关,与重要值成负相关,则显示空间资源对群落特征的影响与自然植被是相似的;(4)聚类分析与主分量分析反映了人工绿地的群体特征,分类结果与功能区划分基本一致,个别样地则不一致;无论格局多样化,还是格调较为均一的绿色景观,均反映了人文美学价值取向对绿地建设的影响;(5)整体上看,南宁市植被结构还存在较大的优化空间。     

Ecological effects of multi‐species,ant–hemipteran mutualisms in citrus

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Camera trapping surveys of forest mammal communities in the Eastern Arc Mountains reveal generalized habitat and human disturbance responses

Large-bodied mammals are a rich and diversified faunal group in tropical rainforests. However, knowledge on community size and composition, and on species’ distribution and ecology remains often scant and inadequate against their chronic status of threats. We used camera trapping to detect mammals in the forests of the Eastern Arc Mountains (EAM) of Tanzania, a world renowned region for biodiversity comprised by a series of distinct and ancient mountain ranges partially covered in moist montane forest. We conducted surveys from 2003 to 2011 in eight of the 12 mountain blocks in Tanzania, and, through an overall sampling effort of 11,500 camera days, we detected 43 species. We normalized species richness and species’ detection events by effort, and used these metrics to assess the effect of habitat and human disturbance variables. We found that rarefied richness is positively affected by forest area at the block level, and that richness at forest patch level is also affected by forest area as well as surrounding human density (negative effect). For a subset of 17 species, we found consistent patterns of avoidance or tolerance of human disturbance and forest edges, and increased occurrence in areas at higher elevation, matching the historical forest loss that in most mountains occurred at lower elevation. Our study provides ecological insights that are novel for most species and sites, and reveals a general trend of negative impact of human disturbance on both community size and species’ relative abundance. Increased protection of the EAM forests in Tanzania is of urgent importance for the persistence of diversified mammal communities.     

Aphid honeydew and its effect on the phyllosphere microflora of Picea abies (L.) Karst

Aphids of the genus Cinara, feeding on Norway spruce, excrete copious amounts of honeydew, a carbon-rich waste product, which accumulates locally on needles and twigs. We investigated the role of honeydew as a potential source of energy which might promote the growth of micro-organisms in the phyllosphere of conifer trees. To approach this question, we followed the population dynamics of Cinara spp. in a natural forest stand over two seasons. We also studied the amounts of honeydew produced by individual aphids and identified potential parameters which might influence honeydew production. Finally, we determined the growth of micro-organisms on infested and uninfested needles of Norway spruce during the growing season. Confined to Picea abies, the investigated Cinara species only became abundant in midsummer, when needles and shoots were expanding. The populations showed only a single peak in abundance, the timing and magnitude of which may vary from year to year due to weather conditions, changes in plant quality in a yearly cycle or the impact of natural enemies. The amount of honeydew produced by individual aphids was dependent on the developmental stage of the aphid, the nutritional supply of its host plant and on the developmental state of the Norway spruce (e.g. bud burst, end of shoot extension). The presence of honeydew significantly increased the growth of bacteria, yeast and filamentous fungi on the surface of needles and there was a pronounced seasonal trend, with the highest abundance in midsummer correlating with the period of peak aphid abundance. Taken together, these findings indicate that aphids have an influence on microbial ecology in the phyllosphere of trees. The implication of our study, from interactions at the population level to effects and potential consequences for C and N fluxes at the level of forest ecosystems, is discussed.