Wasp community responses to habitat complexity in Sydney sandstone forests

Abstract Habitat structure and complexity affect the diversity and composition of fauna in a number of systems. We investigated patterns in wasp species richness, abundance and composition and also their associations with habitat complexity in Sydney sandstone forests, Australia. Pitfall and flight‐intercept traps collected dissimilar wasp assemblages. High complexity habitats supported greater abundance and species richness and a dissimilar composition of pitfall‐trapped wasps to low complexity habitats. Soil moisture, tree canopy cover, ground herb cover and shrub canopy cover all had significant positive associations with the species richness of pitfall‐trapped wasps. Although the five most abundant families of wasps we trapped are endoparasitoids of other arthropods, they showed a variety of preferences for habitat variables. The mechanisms driving associations between habitat complexity and patterns in wasp communities may also provide a basis for understanding factors influencing the regulation of arthropod assemblages by wasps in agricultural and natural landscapes.     

Habitat structure components are effective predictors of trap-nesting Hymenoptera diversity

Habitat heterogeneity can be the major factor affecting species diversity in a community and measuring bee and wasp community habitat preferences in natural systems may provide insights for biodiversity management and conservation. In the present study, we investigate the effects of habitat structure components on solitary bee and wasp species richness and abundance. The research was conducted in an urban forest remnant in southeast Brazil. Our main questions were: (1) is similarity in habitat structure mirrored by similarity in Aculeate assemblage composition? and (2) what are the vegetation features that could be used as predictors of solitary bee and wasp richness and abundance? Aculeate bees and wasps were sampled using trap nests from February to November 2004. Trap nests were placed in sampling units located in 6 ha of secondary mesophytic forest. One hundred and thirty-seven trap nests were occupied by four species of wasps and seven species of bees. Altogether, our sampling units had a mean capture rate (relative to expected richness) of 72% during all the study period. The more similar sampling units were in terms of vegetation structure, the more similar they were in solitary bee and wasp species composition. The variance of tree abundance, shrub height and the abundance of wood logs were good predictors of solitary bee and wasp species richness and abundance in the study area. We demonstrate that even in a small scale it is possible to detect significant influences of habitat features on alpha diversity and that some of them are effective as predictors of trap-nesting Hymenoptera richness and abundance.     

Restore it,and they will come: trap-nesting bee and wasp communities (Hymenoptera: Aculeata) are recovered by restoration of riparian forests

Riparian forests have been greatly affected by anthropogenic actions with formerly continuous riparian forests being slowly converted into small and isolated patches. Riparian forests are extremely important habitats for many groups of insects, including bees and wasps, because they are sources of shelter and food for them and their offspring. There is a growing body of evidence of success in the restoration of riparian forest plant communities; however, little research has been done on the associated invertebrate communities. We test whether restoring plant communities is sufficient for restoring the taxonomic composition of trap-nesting bees and wasps and which functional traits are favored in different sites. We predict that species richness, abundance, and community composition of trap-nesting bees and wasps of riparian sites undergoing restoration will converge on the “target” of a reference site with increasing time, since restoration increases habitat complexity. We also predict that the width of restored patches will also influence the species richness, abundance and community composition of trap-nesting bees and wasps. Bee richness and abundance, and wasp richness, were strongly related to fragment width, but not to age since restoration. Our results indicate that although restored sites are relatively small and scattered in a fragmented landscape, they provide suitable habitat for re-colonization by community assemblages of trap-nesting bees and wasps and the traits selected captured the responses to the habitat restoration. Hence, restored riparian areas can be considered important habitats for invertebrates, thus contributing to an increase in local biodiversity and, possibly, the restoration of some of the ecosystem services they originally provided.     

Contrasting Patterns of Species Richness and Composition of Solitary Wasps and Bees (Insecta: Hymenoptera) According to Land‐use

Several species of arthropods inhabiting forest fragments interact with managed areas. The importance of such areas to biodiversity conservation, however, is not well established. Communities of solitary wasps and bees (Insecta: Hymenoptera) play a key role in agroecosystem functioning and they have been used in studies of biodiversity assessment in different land‐use types. We aimed to assess patterns of species richness and composition of solitary wasps and bees over a 1‐yr period in a gradient of decreasing land‐use intensity formed by pastures, alley croppings, young fallows, and old fallows using trap nests. Old fallows had the highest species richness of wasps and bees, harboring all bee species and 86 percent of wasp species occurring in the region, while the remaining land‐uses had similar species richness. Vegetation structure (tree richness) and relative humidity explained most of the variance for the species richness of wasps. For bees, however, there was no influence of environmental factors on the community among land‐use types, indicating better adaptability of this group to environmental variations related to land‐use. The composition of solitary wasp communities (but not those of bees) differed among land‐use types, and the occurrence of rare species in most cases was restricted to old fallow sites. In conclusion, the community of solitary wasps and bees is contingent on land‐use, with solitary wasps more sensitive to anthropized areas. For both groups, less anthropized areas harbor a greater richness and number of rare species while more intensively managed land‐use types harbor higher abundances.     

An overview of proximate factors affecting the nesting behavior of solitary wasps and bees (Hymenoptera: Aculeata) in preexisting cavities in wood

Guilds of Aculeate solitary wasps and bees that nest in preexisting cavities in wood are important components of terrestrial ecosystems because they engage in several ecological interactions (e.g. predation and pollination) with other species of plants and animals. Spatial and temporal variations in richness and abundance of solitary wasps and bees can be related to changes in environmental structure and in the diversity of other groups of organisms. The nesting period of these Aculeata is their most critical life cycle stage. Females of solitary wasp and bee species invest relatively more time constructing and provisioning their nests than do females of social species. Differently from species that nest in the soil or construct exposed nests, the main factors affecting the reproductive success of solitary species nesting in preexisting wood holes are still unknown. Our objective is to provide an overview of the role of proximate causes of nesting failure or success among solitary wasps and bees (Aculeata), for designing effective conservation and management strategies for these Hymenoptera.     

On a habitat structure-based approach to evaluating species occurrence: cavity-nesting Hymenoptera in a secondary tropical forest remnant

Measuring bee and wasp community habitat preferences in natural systems may provide insights for biodiversity management and conservation as habitat heterogeneity can be the major factor affecting species diversity in a community. Here, we present evidence that supports the use of a vegetation structure-based approach in order to predict the occurrence of common Brazilian-remnant solitary bee and wasp species. Using trap nests, we sampled Aculeate bees and wasps in a forest remnant within an urban area of southeast Brazil. We also measured eight habitat structure components in the area. Tree trunk circumference, shrub and wood log abundance were good predictors of presence or absence of the commonest solitary bee and wasp species in the study area. We demonstrated that even on a small scale it is possible to detect significant influences of habitat structural features on species occurrences and that some of them are effective as surrogates for predicting trap-nesting Hymenoptera occurrence in a given area. Our data present evidence on the potential application of a habitat structure-based approach in conservation assessments concerning cavity-nesting Hymenoptera. We caution, however, that this habitat structure-based approach must to be taken with prudence as a detailed survey of an area’s biodiversity is always preferable.     

Spillover of trap-nesting bees and wasps in an urban–rural interface

A mismatch of resource availability in certain periods can lead to spillover of insects between habitats, resulting in temporal differences in insect diversity. Urban gardens are important anthropogenic habitats but it is unknown whether, when and why spillover of beneficial insects occurs between gardens and agricultural habitats. We used trap nests for Hymenoptera to monthly monitor bee and wasp abundance and species richness in 12 gardens and 12 rapeseed fields. Half of the gardens and rapeseed fields were located in the urban–rural interface and bordered each other (a garden paired with a rapeseed field) and the other half were isolated in the rural landscape (isolated rapeseed fields) and in the urban city centre (isolated gardens). In general, gardens in the urban–rural interface comprised the highest richness of bees and wasps. The abundance of bees but not of wasps was highest in paired habitats and peaked at full rapeseed blooming, indicating that mass-flowering rapeseed offers foraging resources for bees nesting in adjacent gardens. Thus, bees nest and increase their populations in both areas, benefiting from the mass-flowering resource in the agricultural habitat as well as the nesting resources from gardens, suggesting spillover of bees but not of wasps between paired gardens and rapeseed fields. Our study highlights the value of gardens in the urban–rural interface for the biodiversity of functionally important insects. Implementing urban gardening and small-scale agriculture in cities and suburban habitats can promote local pollinator populations and benefit adjacent croplands.     

Parasitoid wasp communities on oil palm plantation: Effects of natural habitat existence are obscured by lepidopteran abundance

The existence of natural habitat around agroecosystem plays a pivotal role in maintaining the presence of natural enemies especially parasitoids. Natural habitat can fail to support biological pest control in agroecosystem due to a particular condition. The objective of this research was to investigate the effect of natural habitat existence on parasitoid wasp communities in oil palm plantation. The ecological research was conducted in the oil palm plantation located in Central Borneo, Indonesia. Twelve plots of oil palm plantations with different habitat characteristics were selected. Insects were sampled using canopy knockdown fogging with a pyrethroid insecticide. In total, 237 species and 2669 individuals of parasitoid wasps belong to 15 families were collected from all research areas. The results showed that species richness and abundance of parasitoid wasps in oil palm plantation was affected by lepidopteran abundance and not by the existence of natural habitat. However, the distance and area of natural habitat influenced the species composition of parasitoid wasps. We concluded that the existence of natural habitat still can maintain the parasitoid wasps in oil palm plantation. Thus, efforts on maintaining parasitoid wasp diversity for management of biological control in oil palm plantation need to pay attention by conserving the natural habitats.     

Diversity and community structure of social wasps (Hymenoptera: Vespidae) in three ecosystems in Itaparica island, Bahia State, Brazil

We studied the structure and composition of communities of social wasps associated with the three insular ecosystems: mangrove swamp, the Atlantic Rain Forest and the 'restinga'- lowland sandy ecosystems located between the mountain range and the sea. Three hundred and ninety-one nests of 21 social wasp species were collected. The diversity of wasps found in each ecosystem was significantly correlated to the diversity of vegetation in each of the three physiognomies, (r(2) = 0.85; F(1.16) = 93.85; P < 0. 01). The Tropical Atlantic Forest physiognomy had higher species richness (18 species), followed by the restinga (16 species) and the mangrove (8 species) ecosystems.     

Spatial configuration and landscape context of wildflower areas determine their benefits to pollinator α- and β-diversity

Wildflower areas have become a staple tool within agro-environmental schemes (AES) to counteract pollinator declines. While their role in providing food resources to resident flower-visiting insects is unambiguous, the conservation effectiveness in a landscape context is less clear. Particularly, how multiple vs. single wildflower area utilization differs between simple and complex landscapes is understudied. We examined colonisation and community dynamics of wild bees and hoverflies in 33 newly established wildflower areas across a gradient of landscape complexity (amount of semi-natural habitat) and connectivity (presence of additional wildflower areas) for seven weeks during three consecutive years (one year during and two after establishment). We recorded more than 25% of the wild bee and hoverfly species of Hesse in an area of approx. 10 ha, substantiating the general benefit of wildflower areas to pollinators. While alpha-diversity increased with landscape complexity in isolated wildflower areas, the opposite pattern was observed for connected areas. The low alpha-diversity in complex landscapes indicated a dilution effect between connected sites. The inverse relationship between alpha and beta diversity among wildflower areas within landscapes suggests interspecific trade-offs between local resource conditions and landscape context. Accordingly, the establishment of multiple wildflower areas within AES is advisable to increase connectivity of suitable habitats in simple landscapes. Moreover, adjusting local conditions (plant diversity) to landscape context likely optimizes conservation effectiveness in modern agroecosystems.     

Multitrophic effects of experimental changes in plant diversity on cavity-nesting bees, wasps, and their parasitoids

Plant diversity changes can impact the abundance, diversity, and functioning of species at higher trophic levels. We used an experimental gradient in grassland plant diversity ranging from 1 to 16 plant species to study multitrophic interactions among plants, cavity-nesting bees and wasps, and their natural enemies, and analysed brood cell density, insect diversity (species richness), and bee and wasp community similarity over two consecutive years. The bee and wasp communities were more similar among the high (16 species) diversity plots than among plots of the lower diversity levels (up to 8 species), and a more similar community of bees and wasps resulted in a more similar community of their parasitoids. Plant diversity, which was closely related to flower diversity, positively and indirectly affected bee diversity and the diversity of their parasitoids via increasing brood cell density of bees. Increasing plant diversity directly led to higher wasp diversity. Parasitism rates of bees and wasps (hosts) were not affected by plant diversity, but increased with the diversity of their respective parasitoids. Decreases in parasitism rates of bees arose from increasing brood cell density of bees (hosts), whereas decreasing parasitism rates of wasps arose from increasing wasp diversity (hosts). In conclusion, decreases in plant diversity propagated through different trophic levels: from plants to insect hosts to their parasitoids, decreasing density and diversity. The positive relationship between plant diversity and the community similarity of higher trophic levels indicates a community-stabilising effect of high plant diversity.     

Disturbance effects on community structure of Ficus tinctoria fig wasps in Xishuangbanna, China: Implications for the fig/fig wasp mutualism

Abstract  Fig trees are important components of tropical forests, because their fruits are eaten by so many vertebrates, but they depend on pollinating fig wasps to produce mature fruits. Disturbance to habitat structure can have a major impact on insect diversity and composition, potentially reducing fruit yields. We investigated the impact of habitat disturbance on the fig wasp community associated with male figs of Ficus tinctoria in Xishuangbanna, China. The community comprised one pollinator species Liporrhopalum gibbosae and six non-pollinating wasp species: Sycoscapter sp.1, Philotrypesis ravii , Philotrypesis sp.1, Neosycophila omeomorpha , Sycophila sp.1, and Walkerella sp.1. More disturbed areas were characterized by higher temperatures, less shade, and more vehicle noise. The response of the fig wasp community was complex, with no simple relationship between intensity of disturbance and pollinator abundance. However, the sex ratios (proportion of male progeny) of pollinators increased significantly in more disturbed areas. We conclude that potential changes in fig wasp community composition brought about by disturbance, are unpredictable, with unclear consequences for tropical rainforest biodiversity.     

Butterfly diversity at the ecotone between agricultural and semi‐natural habitats across a climatic gradient

Aim Understanding the response of species to ecotones and habitat edges is essential to designing conservation management, especially in mosaic agricultural landscapes. This study examines how species diversity and composition change with distance from semi‐natural habitats, over ecotones into agricultural fields, and how within‐site patterns of community transition change across a climatic gradient and differ between crop types. Location A total of 19 sites in Israel where semi‐natural habitats border agricultural fields (wheat fields or olive groves) distributed along a sharp climatic gradient ranging between 100 and 800 mm mean annual rainfall. Methods  We performed butterfly surveys in 2006. We analysed species richness (α‐diversity), diversity, community nestedness and species turnover (β‐diversity) within sites and between sites (γ‐diversity). We also assessed where species of conservation concern occurred. Results In wheat sites, richness and diversity declined abruptly from ecotones to fields and remained homogenously poor throughout the fields, regardless of climate. In olive sites, despite the sharp structural boundary, richness and diversity remained high from the semi‐natural habitat to the grove margins and then declined gradually into groves. Species of conservation concern occurred across all habitats at olive sites, but none were found inside wheat fields or at their ecotones. The contrast in community structure between semi‐natural habitats and fields was affected by both climate and field type. Irrigation in arid regions did not augment species diversity. Main conclusions Our results indicate that consideration of crop type, within a climatic context, should receive high priority in biodiversity conservation in agricultural areas. In ‘hostile’ crops, such as wheat, we suggest favouring a combination of high‐intensity management and wide margins over less intensive management without margins, which may merely aid generalist butterfly species. The scarcity of butterflies in arid irrigated fields suggests a need to carefully assess the effects of irrigation and agrochemicals on species’ communities.     

Abundance of wasps and prey consumption of paper wasps (Hymenoptera, Vespidae : Polistinae) in Northland, New Zealand

Polistine and vespine wasps were captured in Malaise traps in two fire-modified shrubland habitats of varying canopy height and composition at Lake Ohia, Northland, New Zealand. Prey consumption rates were calculated for the Asian paper wasp (Polistes chinensis antennalis) occupying these two areas of shrubland and a home garden in Whangarei, Northland. The sites were systematically searched for nests and wasp prey determined by intercepting foragers returning to nests. The Asian paper wasp predominated in the Malaise trap samples from the low- growing habitat while the German wasp (Vespula germanica) was more common in the taller vegetation type. The Asian paper wasp was more abundant than the German wasp in the samples in February and early March. Only four Australian paper wasps (Polistes humilis) and no common wasps (Vespula vulgaris) were caught. Asian paper wasps collected an estimated 15 000 prey loads per ha per season from one of the shrubland areas, and 478 000 prey loads per ha per season from the second area. These convert to estimates of 31 and 957 g per ha per season of invertebrate biomass removed by paper wasps from each habitat, respectively. The estimate for the garden site was 79 g per ha per season. Wasp nest densities varied between 20 and 210 nests per hectare. The biomass estimates are similar to average figures calculated for vespine wasps in scrubland and pasture. Both Asian paper wasps and Australian paper wasps preyed mainly on lepidopteran larvae. The cabbage white butterfly (Pieris rapae) was the most commonly collected species. Noctuid species were also well represented. Both male and female Asian paper wasps collected nectar in late March and early April.     

Rodent Diversity and Land Use in Montebello,Chiapas, Mexico

We analyzed the abundance and diversity of Heteromyid and Murid rodents in the Lagos de Montebello National Park and adjacent areas, Chiapas, Mexico. We sampled three habitat types with different degrees of disturbance: pine-oak-liquidambar forest, ecotone and crop farming lands. Habitat types were defined considering characteristics such as heterogeneity, structural complexity and arboreal cover. We obtained ancillary habitat data considered important for small mammal requirements. Data on rodent communities were obtained by capture-mark-recapture between February and October 1996. We made 410 captures in 3820 trap-nights effort. Ten species were recorded, including one endemic with restricted distribution in Chiapas. Mouse diversity in the forest was significantly higher than within the farm lands. A Kendall correlation analysis showed positive relationship between rodent community species richness and habitat heterogeneity. Diversity of rodents was associated with the habitat complexity and structural elements, and negatively correlated with farming intensity. We found a high beta diversity and low similarity of the rodent communities in the three different habitats. Community composition strongly changed from the forest through the ecotone into the farm lands, with five species gained and seven species lost. The highest species richness was found in the ecotone; however, it showed a strong dominance of a single species that can convert into a plague of crops, and relatively low abundance of the other species. The pine-oak-liquidambar forest had the highest diversity indices, sheltering a particular rodent community within the study area, it therefore probably has the most important role in the conservation of the local biodiversity.     

Interacting effects of landscape context and habitat quality on flower visiting insects in agricultural landscapes

Landscape context and habitat quality may have pronounced effects on the diversity of flower visiting insects. We investigated whether the effects of landscape context and habitat quality on flower visiting insects interact in agricultural landscapes in the Netherlands. Landscape context was expressed as the area of semi-natural habitats or the density of linear landscape features, and was quantified at spatial scales ranging from 250 to 2000 m. Habitat quality was determined as flower abundance. Species richness and abundance of hoverflies and bees were determined along 16 stream banks experiencing similar environmental conditions but situated in areas with contrasting landscape context. Only flower abundance and the area of semi-natural habitats within 500–1000 m were significantly related to species richness of hoverflies and bees and these factors had interacting effects on both species groups. Our results suggest that the regional area of semi-natural habitats had a positive effect on hoverfly species richness when flower abundance was relatively high, but not when flower abundance was low. Moreover, flower abundance had positive effects on hoverfly species richness only in areas with relatively many semi-natural habitats. Contrastingly, flower abundance had a more positive effect on bee species richness in landscapes with few semi-natural habitats compared to landscapes with more semi-natural habitats. Our results suggest that the importance of landscape context for the species richness of flower visiting insects depends upon the quality of the habitat patches.     

Trap-Nesting Hymenoptera and Their Network with Parasites in Recovered Riparian Forests Brazil

Different aspects of human activities can cause environmental change that endanger species persistence, alter species distributions, and lead to changes in antagonistic and mutualistic interactions, whereas deforestation and flooding of riparian forest results in landscapes consisting of patchily distributed riparian forest fragments in a matrix of pastures, plantations, and urban areas. Therefore, we assessed the richness, abundance, and trophic interactions of trap-nesting Hymenoptera and their parasites at four patches of restored riparian forest and at one reference natural fragment, of different sizes and ages, located at the Volta Grande Reservoir, in Minas Gerais and São Paulo states to answer the following questions: (1) Does the richness and abundance of cavity-nesting bees and wasps differ in riparian forest fragments according to the seasonal periods? (2) Does the composition of cavity-nesting bees and wasps vary among restoration and reference sites and between climate seasons (wet and dry)? (3) How do the degrees of specialization of the parasites vary among the patches of forest? We recorded 12 species of wasps, eight of bees, and nine species of parasites. Areas with longer time since restoration (reference site) showed higher species richness. However, the abundance was higher in most recent areas. The composition of bee and wasp assembly has not significantly changed between the climate seasons, although it is different between sampling areas. The richness and abundance were higher in warmer and rainy periods. The rate of bee and wasp mortality was high. The degree of specialization of parasites varies among sampling units, and the network of host-parasite interaction has a modular configuration with generalists and specialists. We concluded that the restored areas with more complex habitat could provide better conditions for the reestablishment of ecological interactions among these insects, the local flora, and other invertebrates, which together contribute to the success of the restored environments.     

High Bee and Wasp Diversity in a Heterogeneous Tropical Farming System Compared to Protected Forest

It is a globally important challenge to meet increasing demands for resources and, at the same time, protect biodiversity and ecosystem services. Farming is usually regarded as a major threat to biodiversity due to its expansion into natural areas. We compared biodiversity of bees and wasps between heterogeneous small-scale farming areas and protected forest in northern coastal Belize, Central America. Malaise traps operated for three months during the transition from wet to dry season. Farming areas consisted of a mosaic of mixed crop types, open habitat, secondary forest, and agroforestry. Mean species richness per site (alpha diversity), as well as spatial and temporal community variation (beta diversity) of bees and wasps were equal or higher in farming areas compared to protected forest. The higher species richness and community variation in farmland was due to additional species that did not occur in the forest, whereas most species trapped in forest were also found in farming areas. The overall regional species richness (gamma diversity) increased by 70% with the inclusion of farming areas. Our results suggest that small-scale farming systems adjacent to protected forest may not only conserve, but even favour, biodiversity of some taxonomic groups. We can, however, not exclude possible declines of bee and wasp diversity in more intensified farmland or in landscapes completely covered by heterogeneous farming systems.     

Distribution of ground-dwelling beetles in fragmented tropical habitats

The conservation of biodiversity is increasingly dependent on human-altered habitats. In a fragmented forest landscape in northern Costa Rica within the Mesoamerican Biological Corridor, an area of great conservation importance, we compared the diversity and composition of ground-dwelling beetle communities in five habitat types along a gradient of increasing disturbance: primary forest, logged forest, secondary forest, plantation (Gmelina arborea) and pasture. Using pitfall trapping we captured a total of 1,877 beetles (Coleoptera), comprising 422 morphospecies in 26 families. The plantation sites had the lowest number of species followed by secondary forest and pasture. Multivariate analysis separated the beetle fauna according to land use, and suggested that only the logged forest maintains a similar species assemblage to primary forest. However, each habitat harboured a number of unique species indicating the conservation value of the mosaic of habitats found in fragmented landscapes. Our results suggest that to maintain forest beetle species diversity it is essential that areas of natural forest are conserved. However, other land uses also provide beetle habitats and in fragmented areas active management to maintain a mosaic of land uses will contribute to the conservation of beetle diversity.