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1.
If spatial patterns of change within a habitat were similar for both vertebrates and insects, then vertebrates would provide useful surrogates for designing reserves for the conservation of invertebrates. Data from two eucalypt habitats were analysed to determine levels of habitat richness, site richness and species turnover in birds and insects. For birds the relatively low species richness and turnover indicated that sites within the habitat were similar in composition. In wet eucalypt forests Diptera were very speciose with over 1,000 morphospecies sorted. Species turnover was slightly higher than for birds, indicating a large number of species change from site to site. In dry eucalypt woodland, insects trapped through the winter months were not speciose but turnover between sites was very large. This suggests reserves designed to conserve insects may need to be larger than for birds in order to include the high site variability and richness of insect communities.Spatial patterns of birds and insects were investigated further, to determine if sites that were closer together were more similar for both birds and insects. No patterns were found for birds in either habitat suggesting birds are not responding to changes in the environment at this scale. Diptera in wet eucalypt forest showed higher similarity between close sites than distant sites, while for winter insects in dry eucalypt woodland the relationship was significant when two outlier points were removed. Overall, birds are not good surrogates for insects in either habitat as no relationship between birds and insects in site-to-site similarity was found.  相似文献   

2.
紫胶虫蜜露对地表蚂蚁多样性的影响   总被引:2,自引:0,他引:2  
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.  相似文献   

3.
《新西兰生态学杂志》2011,29(1):105-115
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.  相似文献   

4.
5.
Combined studies of the communities and interaction networks of bird and insect pollinators are rare, especially along environmental gradients. Here, we determined how disturbance by fire and variation in sugar resources shape pollinator communities and interactions between plants and their pollinating insects and birds. We recorded insect and bird visits to 21 Protea species across 21 study sites and for 2 years in Fynbos ecosystems in the Western Cape, South Africa. We recorded morphological traits of all pollinator species (41 insect and nine bird species). For each site, we obtained estimates of the time since the last fire (range: 2–25 calendar years) and the Protea nectar sugar amount per hectare (range: 74–62 000 g/ha). We tested how post-fire age and sugar amount influence the total interaction frequency, species richness and functional diversity of pollinator communities, as well as pollinator specialization (the effective number of plant partners) and potential pollination services (pollination service index) of insects and birds. We found little variation in the total interaction frequency, species richness and functional diversity of insect and bird pollinator communities, but insect species richness increased with post-fire age. Pollinator specialization and potential pollination services of insects and birds varied differently along the environmental gradients. Bird pollinators visited fewer Protea species at sites with high sugar amount, while there was no such trend for insects. Potential pollination services of insect pollinators to Protea species decreased with increasing post-fire age and resource amounts, whereas potential pollination services of birds remained constant along the environmental gradients. Despite little changes in pollinator communities, our analyses reveal that insect and bird pollinators differ in their specialization on Protea species and show distinct responses to disturbance and resource gradients. Our comparative study of bird and insect pollinators demonstrates that birds may be able to provide more stable pollination services than insects.  相似文献   

6.
Complex distribution patterns of species-rich insect communities in tropical rainforests have been intensively studied, and yet we know very little about processes that generate these patterns. We provide evidence for the key role of homopteran honeydew and plant nectar in structuring ant communities in an Australian tropical rainforest canopy and understorey. We also test the ant visitation of these resources against predictions derived from the 'ant-mosaic' hypothesis. Two ant species were highly dominant in terms of territorial behaviour and abundance: Oecophylla smaragdina and Anonychomyrma gilberti . Both dominant ant species monopolised large aggregations of honeydew-producing homopterans. Attended homopteran species were highly segregated between these two ant species. For the use of extrafloral and floral nectar (involving 43 ant species on 48 plant species), partitioning of ant species among plant species and between canopy and understorey was also significant, but less pronounced. In contrast to trophobioses, simultaneous co-occurrence of different nectar foraging ant species on the same plant individuals was frequent (23% of all surveys). While both dominant ant species were mutually exclusive on honeydew and nectar sources, co-occurrence with non-dominant ant species on nectaries was common. The proportion of visits with co-occurrences was low for dominant ants and high for many sub-ordinate species. These findings support the ant mosaic theory. The differential role of honeydew (as a specialised resource for dominant ants) and nectar (as an opportunistic resource for all ants including the co-occurring non-dominant species) provides a plausible structuring mechanism for the Australian canopy ant community studied.  相似文献   

7.
Food resources can limit populations of insectivorous birds. Previous studies have shown strong correlations between bird population densities and their invertebrate food, with declining populations being attributed to loss of prey. This might also be the case for the threatened Knysna warbler (Bradypterus sylvaticus), which in the last 20 years has declined precipitously on the Cape Peninsula, South Africa. The bird is abandoning natural, protected forests, retreating to narrow belts of suburban, riverine woodland with dense, tangled understoreys. The potential invertebrate food availability in natural forests and suburban woodland was assessed against what is known of the bird’s preferred prey. The invertebrate food resource spectrum and abundance were determined using three sampling techniques in both natural forest and suburban woodland. Despite greater overall abundance of invertebrates in suburban woodland, the warbler’s preferred prey items were equally abundant in both habitats. This suggests that reduced food supply does not explain abandonment of natural forests by the warbler. Rather, it is concluded that the availability of suitable nesting substrata, which are more abundant in suburban woodland, has driven the biotope shift. This is an unusual case of a localized and threatened bird species faring better under transformed conditions than in natural habitats.  相似文献   

8.
王思铭  陈又清 《昆虫知识》2011,48(1):183-190
同翅目昆虫多为植食性害虫,但有些种类也是重要的经济昆虫。以蜜露为纽带,蚂蚁与排泄蜜露的同翅目昆虫在漫长的进化过程中逐渐形成了复杂而密切的关系。研究蚂蚁-同翅目昆虫之间的相互作用,有选择的防治或保护某些同翅目昆虫,并控制其在寄主植物上的数量,可提高经济效益。本文介绍蚂蚁与排泄蜜露的同翅目昆虫的相互作用,以及相互作用对节肢动物群落和寄主植物产生的生态学效益,提出研究过程中的不足,并探讨蚂蚁-同翅目昆虫之间的相互作用在生物防治、生物多样性及生态系统功能方面的重要意义,以促进种间关系研究的进一步发展。  相似文献   

9.
Insectivorous birds are known to play a decisive role for the natural control of herbivorous insects. Thus, they enhance the growth, reproduction, and survival of plant individuals and in the long‐term benefit plant regeneration. However, particularly in the tropics, forest fragmentation has been suggested to cause a loss of insectivorous birds. Yet, it is unclear whether this hampers the trophic control of herbivorous insects with potential consequences for plants. Therefore, we investigated the effect of increasing forest fragmentation on tritrophic interactions between insectivorous birds, herbivorous insects, and plants in a subtropical forest landscape, South Africa. We monitored the community composition of birds and estimated insectivorous bird abundances along a gradient of forest fragmentation. In the same sites, we installed bird exclosures on a common plant species (Englerophytum natalense) to assess effects of the trophic control of insectivorous birds on herbivorous insects and leaf area loss (LAL). Forest fragmentation strongly shaped the functional composition of bird communities, particularly through a loss of forest‐dependent insectivorous birds. Moreover, LAL was higher within bird exclosures than on control branches and increased with increasing forest fragmentation on the control branches. Altogether, forest fragmentation seems to hamper the trophic control of herbivorous insects by insectivorous birds through changes in the community composition. This, in turn, may interfere with tritrophic interactions and ecological processes. Thus, conservation efforts aiming at enhancing the natural control of herbivorous insects should focus on the maintenance of continuous indigenous forests that are well‐connected to smaller forest fragments on the landscape scale.  相似文献   

10.
Water level and water surface area fluctuations are important factors determining abundance of bird populations and bird assemblages structure in a wetland habitat. The water level and water surface area of the Marsh T?m?rd (West Hungary) changed drastically between 1998 and 2008, and the marsh dried out because of scarce rainfall in 2000 and 2001. A habitat restoration in winter 2001 repaired the waterholding capacity of the marsh. We analyzed changes in parameters of bird assemblages in investigated wetland area in relation of environmental factors. We used full redundancy analysis (RDA) on number of caugth migratory birds per year, species richness, diversity and evenness of bird assemblages to examine correlations among water level, water surface area and vegetation core. Species like water rail, common snipe, river warbler, Savi’s warbler, great reed warbler, reed warbler, marsh warbler, sedge warbler, reed bunting showed high and positive linear correlations with the water level and water surface area in the postbreeding period. Some wetland species, sedge warbler, Savi’s warbler and reed bunting as well as total number of caugth birds per year and total numbers of caugth species per year were clearly associated with thick marsh vegetation. According to our results the bird species composition of the wetland might have returned to the prerestoration levels and surface areas.  相似文献   

11.
Insect outbreaks are major natural disturbance events that affect communities of forest birds, either directly by affecting the food supply or indirectly by changing the vegetation composition of forest canopies. An examination of correlations between measures of bird and insect abundance across different spatial scales and over varying time lag effects may provide insight into underlying mechanisms. We developed a hierarchical Bayesian model to assess correlations between counts of eight warbler species from the Breeding Bird Survey in eastern Canada, 1966 to 2009, with the presence of spruce budworm (Choristoneura fumiferana Clem.) at immediate local scales and time‐lagged regional scales, as measured by extent of defoliation on host tree species. Budworm‐associated species Cape May warbler (Setophaga tigrina), bay‐breasted warbler (Setophaga castanea), and Tennessee warbler (Oreothlypis peregrina) responded strongly and positively to both local and regional effects. In contrast, non‐budworm‐associated species, Blackburnian warbler (Setophaga fusca), magnolia warbler (Setophaga magnolia), Canada warbler (Cardellina canadensis), black‐throated blue warbler (Setophaga caerulescens), and black‐throated green warbler (Setophaga virens), only responded to regional effects in a manner that varied across eastern Canada. The complex responses by forest birds to insect outbreaks involve both increased numerical responses to food supply and to longer term responses to changes in forest structure and composition. These effects can vary across spatial scales and be captured in hierarchical population models, which can serve to disentangle common trends from data when examining drivers of population dynamics like forest management or climate change.  相似文献   

12.
Birds and figs are conspicuous members of the tropical and subtropical ecosystems. Because they are easily observed and very speciose, their relationships have been well studied in many areas, and the figs are considered a keystone resource for many bird species which are efficient fig seed dispersers. Taiwan has a relatively high endemism rate for many taxa (17% of bird species) but because of its high human population density, most lowland habitats are heavily developed, of which much of it covered by dense urban habitation. To establish the importance of urban figs for birds, we focused our surveys mostly on three common urban fig species (Ficus caulocarpa, F. microcarpa and F. subpisocarpa). We observed trees with ripening figs from July 2013 to December 2016 in order to determine the composition of the fig-consuming bird community. In addition, we added all the information available in the scientific literature and birdwatchers' observations which we could find. In total, we observed 42 bird species consuming 18 fig species. The bird diversity in urban areas was non-negligible even during winter. Therefore, there are two reasons why figs are important for Taiwan's bird avifauna: in cities, the tree diversity is generally low so that figs provide a stable food resource; and since figs are fruiting all year-round, they are one of the few reliable resources available during winter when many migrant birds overwinter in Taiwan. Already crucial for many species in tropical and subtropical forests, fig trees may also be essential for urban birds in tropical and subtropical regions.  相似文献   

13.
Ants (Hymenoptera: Formicidae) are eaten by a number of bird species in southern Africa. Our database contained 545 species (excluding waterbirds and raptors), of which 179 species have been observed feeding on ants, or had ants in their stomachs. Ants are eaten by birds in all ecosystems, but the consumption of ants is disproportionately high in species that occur in arid ecosystems. The number of bird species eating ants increases in proportion to the number of bird species in any ecosystem, but it increases disproportionately with decreasing mean annual rainfall. There was a small, but not significant, difference in the proportion of ant-eating bird species between 502 resident species, of which 154 (30.6%) eat ants, and 47 nomadic species, of which 18 (38.2%) eat ants. Foraging behaviour and substrate, i.e. whether foraging in the air, from a perch or on the ground, significantly influenced the probability that ants would be included in the diet.  相似文献   

14.
The consequences of habitat alteration on the role of understory insectivorous birds as predators of herbivorous insects in tropical forests are poorly understood. To examine whether fragmentation may affect the top–down controls of herbivory, we compared the number of species, individuals, and the community structure of insectivorous birds between fragments and continuous tropical moist forest in Mexico. We also registered insect herbivore abundances and conducted a larvae predation experiment to evaluate the potential role of insectivorous birds as predators of herbivorous insects. We recorded 63 bird species from 22 families, 43 percent of which were insectivorous birds. Species richness, abundance, and diversity of the avian community were higher in continuous forest compared with forest fragments. For insectivorous birds in particular, there was low similarity in avian insectivore communities between forest types, and forest fragments had more heavily dominated communities of avian insectivores. During the dry season, forest fragments presented significantly higher predation rates on artificial caterpillars, and lower abundance of herbivorous Lepidoptera larvae, compared with continuous forest. Furthermore, there was a significant negative correlation between artificial caterpillar predation rate and larval Lepidoptera abundance, with higher rates of predation in sample sites of low Lepidoptera abundance. Hence, the potentially greater light in the dry season combined with a more dominated avian insectivore community in forest fragments may facilitate increased predation by avian insectivores, resulting in a decline in abundance of larval Lepidoptera, with implications for the process of insect‐driven herbivory in forest fragments.  相似文献   

15.
《新西兰生态学杂志》2011,33(2):138-146
Sap-feeding insects can excrete considerable quantities of sugar-rich honeydew. In New Zealand, South Island beech (Nothofagus spp.) forests are shaped by the extensive honeydew resource produced by two endemic coelostomidiid species (Ultracoelostoma assimile and U.?brittini) and geckos on northern islands are known to feed on the honeydew of a third endemic coelostomidiid, Coelostomidia zealandica. There are six other endemic coelostomidiid species in New Zealand that utilise a range of plant hosts but the ecological role of these species is poorly understood. A survey of mainland forests in the Auckland Ecological Region was conducted in February?April 2006 to investigate the distribution and abundance of coelostomidiids in this area. Three coelostomidiid species were detected in the survey (C.?zealandica, C.?pilosa and C.?wairoensis) and five new host?scale insect associations were identified. C.?zealandica was uncommon, C.?pilosa was widespread in broadleaved?podocarp forest but only formed light infestations, and C.?wairoensis was present in all teatree stands examined, often forming heavy infestations on k?nuka (Kunzea ericoides). Infested k?nuka trees had sooty moulds growing on them and exotic wasps were regularly seen feeding on C.?wairoensis honeydew. The extent and intensity of C. wairoensis infestation on k?nuka suggests it will have community-level impacts.  相似文献   

16.
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.  相似文献   

17.
Climate change is predicted to impact tropical mangrove forests due to decreased rainfall, sea‐level rise, and increased seasonality of flooding. Such changes are likely to influence habitat quality for migratory songbirds occupying mangrove wetlands during the tropical dry season. Overwintering habitat quality is known to be associated with fitness in migratory songbirds, yet studies have focused primarily on territorial species. Little is known about the ecology of nonterritorial species that may display more complex movement patterns within and among habitats of differing quality. In this study, we assess within‐season survival and movement at two spatio‐temporal scales of a nonterritorial overwintering bird, the prothonotary warbler (Protonotaria citrea), that depends on mangroves and tropical lowland forests. Specifically, we (a) estimated within‐patch survival and persistence over a six‐week period using radio‐tagged birds in central Panama and (b) modeled abundance and occupancy dynamics at survey points throughout eastern Panama and northern Colombia as the dry season progressed. We found that site persistence was highest in mangroves; however, the probability of survival did not differ among habitats. The probability of warbler occupancy increased with canopy cover, and wet habitats were least likely to experience local extinction as the dry season progressed. We also found that warbler abundance is highest in forests with the tallest canopies. This study is one of the first to demonstrate habitat‐dependent occupancy and movement in a nonterritorial overwintering migrant songbird, and our findings highlight the need to conserve intact, mature mangrove, and lowland forests.  相似文献   

18.
We studied the indirect effects of an aphid Uroleucon nigrotuberculatum on density and performance of herbivorous insects through tending ants and modification of plant traits on a tall goldenrod Solidago altissima in Japan. To examine ant-mediated indirect effects of the aphid on the leafhopper and geometrid moth caterpillars, we conducted an experiment in which we manipulated aphid densities. The aphid decreased the density of these herbivorous insects through ant-mediated indirect effects, because honeydew scattered by the aphid-attracted ants that then removed them. To examine plant-mediated indirect effects of the aphid on two temporally separated insects, a scale insect and a grasshopper, we compared the density and performance of these herbivorous insects on aphid-inoculated plants and aphid-free plants. Aphid-induced plant modifications had different effects on the scale insect and grasshopper. The aphid indirectly decreased the density and survivorship of the scale insect. On the other hand, the number of grasshoppers increased as a result of the increased number of leaves and the increased nitrogen content induced by prior aphid feeding. However, aphid infestation did not affect the survival of the grasshopper. Thus, the aphid has large indirect effects on co-occurring herbivorous insects through the removal behavior of tending ants and on temporally separated herbivorous insects through changes in quality and quantity of the tall goldenrod.  相似文献   

19.
New Holland honeyeaters collect nectar, manna or honeydew for energy and hawk small flying insects for protein. The insects taken were usually Diptera and Hymenoptera weighing 0.7 mg dry weight or less. Net rates of energy gain from hawking small flying insects were usually less than 20 J min?1 and sometimes negative and insufficient to meet the bird's daily energy requirements. Those from feeding on nectar, manna or honeydew were usually above 40J min?1 and often above 400J min?1 at dawn and the birds depended on these carbohydrates for energy. Nectar, manna and honeydew contained negligible amounts of protein, and the birds used small flying insects as sources of protein, and presumably other nutrients. Given that carbohydrate resources supply better rates of energy gain than insects. New Holland honeyeaters should collect their energy requirements from carbohydrates and only collect sufficient insects to satisfy their protein requirements. Estimates of the food intakes of both non-breeding and breedig birds showed that they did this. Non-breeding New Holland honeyeaters collected from 72 to 125 (mean 92) kJ of carbohydrates per day and 17 to 58 (mean 31) mg of protein per day. These meet the daily energy (75 kJ) and protein (20 mg) requirements of the birds. Breedig birds collected more carbohydrates and more insects, but in proportion to their increased energy and protein requirements respectively. New Holland honeyeaters are probably limited by their ability to meet their energy requirements from nectar, manna or honeydew and not by insects. Non-breeding birds collected their protein requirements in about 10 min of insect-feeding, but spent from 33 to 90% of the day collecting carbohydrates to meet their energy requirements. The maintenance requirement of 20 mg of protein per day for New Holland honeyeaters is about 25% of that estimated from standard equations for a bird of the same size. This low level may have evolved in response to low energy availability.  相似文献   

20.
Abstract. 1. The degree of infestation by New Zealand sooty beech scale insects (Ultracoelostoma assimile, Homoptera: Margarodidae) varies dramatically among adjacent southern beech trees (Nothofagus spp., Fagaceae), but has previously been assumed to be uniformly or randomly distributed within individual host trees. In this study, a full‐census survey was conducted from ground level to canopy level on 14 naturally occurring, canopy‐dominant red beech (Nothofagus fusca) trees (size range 38.7–107.6 cm diameter at breast height) to determine the degree of within‐tree heterogeneity in herbivore density. 2. The within‐tree distribution of the sooty beech scale was vertically stratified and highly heterogeneous, with the greatest densities occurring on bark surfaces in the canopy rather than on the trunk, and on the lower rather than upper sides of the branches. The spatial distribution was strongly negatively correlated with trunk and branch diameter, and increasing bark thickness (as a function of diameter) provides a plausible explanation for differences in the establishment and population density of sooty beech scale insects with trunk and branch size. Furthermore, there was a significant change in the spatial distribution of scale insect populations on trunks and branches of trees of increasing diameter at breast height. This indicates a strong temporal component to the spatial dynamics of the sooty beech scale insect driven by changing host phenology. Future studies on phytophagous insects infesting large host trees need to consider more explicitly changes in population dynamics through space and time. 3. Because of the high degree of within‐tree heterogeneity in population density, the total population size of scale insects on an individual tree could not be predicted from any measure of population density low on the trunk. However, the dry weight biomass of sooty mould fungi growing on the ground beneath infested trees was a remarkably accurate predictor of the total population size of scale insects. The use of sooty mould fungi as a relative measure of population size could be incorporated into studies of other honeydew‐producing hemipterans, since the growth of sooty mould is a distinctive feature synonymous with high concentrations of honeydew production worldwide.  相似文献   

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