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1.
Nontarget species such as pollinators may be of great importance to the restoration process and the long‐term functioning of restored habitats, but little is known about how such groups respond to habitat restoration. I surveyed bee communities at five equal‐aged restored sites, paired with five reference sites (riparian remnants) along the Sacramento River, California, United States. Flower availability and bee visitation patterns were also measured to examine the restoration of pollination function. Restoration of structural vegetation allowed diverse and abundant native bee communities to establish at the restoration sites; however, the composition of these important pollinator communities was distinct from that in the remnant riparian sites. Differences did not arise primarily from differences in the composition of the flowering‐plant community; rather there must be other physical characteristics of the restored sites or differences in nesting site availability that led to the different pollinator communities. Because sites were spatially paired, the differences are unlikely to be driven by landscape context. Bee life‐history and other biological traits may partially explain the differences between bee communities at restored and remnant sites. Patterns of visitation to native plant species suggest that pollination function is restored along with pollinator abundance and richness; however, function may be less robust in restored habitats. An examination of interaction networks between bees and plant species found at both restored and remnant riparian sites showed less redundancy of pollinators visiting some plants at restored habitats.  相似文献   

2.
Understanding biodiversity distribution is a primary goal of community ecology. At a landscape scale, bee communities are affected by habitat composition, anthropogenic land use, and fragmentation. However, little information is available on local-scale spatial distribution of bee communities within habitats that are uniform at the landscape scale. We studied a bee community along with floral and nesting resources over a 32 km2 area of uninterrupted Mediterranean scrubland. Our objectives were (i) to analyze floral and nesting resource composition at the habitat scale. We ask whether these resources follow a geographical pattern across the scrubland at bee-foraging relevant distances; (ii) to analyze the distribution of bee composition across the scrubland. Bees being highly mobile organisms, we ask whether bee composition shows a homogeneous distribution or else varies spatially. If so, we ask whether this variation is irregular or follows a geographical pattern and whether bees respond primarily to flower or to nesting resources; and (iii) to establish whether body size influences the response to local resource availability and ultimately spatial distribution. We obtained 6580 specimens belonging to 98 species. Despite bee mobility and the absence of environmental barriers, our bee community shows a clear geographical pattern. This pattern is mostly attributable to heterogeneous distribution of small (<55 mg) species (with presumed smaller foraging ranges), and is mostly explained by flower resources rather than nesting substrates. Even then, a large proportion (54.8%) of spatial variability remains unexplained by flower or nesting resources. We conclude that bee communities are strongly conditioned by local effects and may exhibit spatial heterogeneity patterns at a scale as low as 500–1000 m in patches of homogeneous habitat. These results have important implications for local pollination dynamics and spatial variation of plant-pollinator networks.  相似文献   

3.
4.
1.  The evaluation of restoration measures is an important task of conservation biology. Inland sand dunes and dry, oligotrophic grasslands have become rare habitat types in large parts of Central Europe and their restoration and management is of major importance for the preservation of many endangered plant and insect species. Within such habitats, it is important to restore key ecosystem services, such as pollination networks. As wild bees are the most important pollinators in many ecosystems, they represent a suitable key group to evaluate restoration measures. Furthermore, the recent decline of many bee species and the potential ecological and economic consequences are currently topics of strong scientific interest.
2.  We studied the succession of bee communities in response to restoration measures of sand dunes and sand grasslands and compared these communities with those of old sand dune complexes.
3.  Our results show that wild bees respond rapidly to restoration measures indicated by a high species richness and abundance. The community structure of bees at restoration sites converged only slightly to those of the target sites. A higher similarity was found between bee communities at the restoration sites (sand dunes and grasslands), indicating that their close proximity was an important determinant of species overlap. Environmental factors such as the number of entomophilous plant species and moisture had a strong influence on wild bee species composition.
4.   Synthesis and applications . The restoration of inland sand dune complexes provides opportunities for colonization by a diverse wild bee community. Although it is difficult to establish a given target community, restoration measures gave rise to a high pollinator diversity and abundance, suggesting that community function can be re-established.  相似文献   

5.
Nesting resources structure native bee communities and the availability of suitable nests may enhance population abundance and persistence. Nesting rates of ground-nesting bees have proven challenging to assess due to a lack of standardized methods. We quantified the abundance of ground-nesting native bees using emergence traps over a seven-month study period. We then compared specimens captured in emergence traps with pan- and net-collected specimens. We hypothesized that ground-nesting bees would be highly similar to bees found foraging within our study site. However, the species assemblage of ground-nesting bees collected from emergence traps was significantly dissimilar from the assemblages collected with aerial nets and pan traps, indicating different sampling methods target different components of the species assemblage. We then examined the importance of nesting resources found at each emergence trap on the abundance of ground-nesting bees collected from emergence traps. Quantification of potential nesting resources, such as percent bare soil, has been proposed as a proxy of nesting habitat for ground-nesting guilds. Sloped ground and soil compaction were the most predictive nesting resources at the community-level. Further, spatial distribution of nesting resources within the study landscape also affected nesting rates, although this varied by species. Bees occurred in 85% of emergence traps, with sampling date strongly affecting the number of bees collected. Emergence traps provide a useful method of sampling the ground-nesting native bee community and investigating nesting incidence.  相似文献   

6.
Bees require distinct foraging and nesting resources to occur in close proximity. However, spatial and temporal patterns in the availability and quantity of these resources can be affected by disturbances like wildfire. The potential for spatial or temporal separation of foraging and nesting resources is of particular concern for solitary wood‐cavity‐nesting bees as they are central‐place, short‐distance foragers once they have established their nest. Often the importance of nesting resources for bees have been tested by sampling foraging bees as a proxy, and nesting bees have rarely been studied in a community context, particularly postdisturbance. We tested how wood‐cavity‐nesting bee species richness, nesting success, and nesting and floral resources varied across gradients of wildfire severity and time‐since‐burn. We sampled nesting bees via nesting boxes within four wildfires in southwest Montana, USA, using a space‐for‐time substitution chronosequence approach spanning 3–25 years postburn and including an unburned control. We found that bee nesting success and species richness declined with increasing time postburn, with a complete lack of successful bee nesting in unburned areas. Nesting and floral resources were highly variable across both burn severity and time‐since‐burn, yet generally did not have strong effects on nesting success. Our results together suggest that burned areas may provide important habitat for wood‐cavity‐nesting bees in this system. Given ongoing fire regime shifts as well as other threats facing wild bee communities, this work helps provide essential information necessary for the management and conservation of wood‐cavity‐nesting bees.  相似文献   

7.
Habitat complexity is directly correlated to insect diversity in most natural environments. Structural complexity reflects an increase in vertical stratification and plant diversity and often leads to a greater availability of floral resources and nesting sites. Efficient conservation strategies require understanding of how changes in habitat structure affect insects that provide essential ecosystem services. We analyzed how the diversity and species composition of bees and wasps that nest in pre-existing cavities is affected by habitat complexity. Our study was developed in the semiarid region of northeastern Brazil, in the Ubajara National Park and surrounding area. Four types of habitats within two physiognomies were sampled for two consecutive years. We used 120 trap-nest (9000 cavities) distributed in 40 sample points. Overall, 657 cavities were occupied by 11 species of bees, nine of wasps, and six of cleptoparasitic/parasitoids. Bees and wasp diversity increases with habitat complexity. While species richness was higher in more complex physiognomies, abundance was higher in disturbed areas. Species composition also varied with habitat structure. Habitat simplification has adverse effects on the diversity and composition of assemblages. These effects are stronger in more complex habitats indicating that conservation of humid habitats within semiarid areas is essential to maintain bee and wasp regional diversity.  相似文献   

8.
In recent years restoration project efforts in arid grasslands of the Pacific Northwest have increased; however, little is known about the bee communities in these areas or how restoration affects them. Native bees provide an essential ecosystem service through pollination of crops and native plants and understanding their response to restoration is a high priority. To address this issue, we conducted a three‐year study in an arid bunchgrass prairie with three objectives: (1) describe the bee community of this unique grassland type and its temporal variability; (2) investigate environmental variables influencing the community; and (3) examine effects of restoration on the community. We identified 62 bee species and found strong seasonal and inter‐annual variation in bee abundance, richness, diversity, and species composition. Unexpectedly, these temporal trends did not correspond with patterns in floral resources; however, several variables were associated with variation in bee abundance, richness, and diversity among sites. Sites with high levels of litter cover had more bees, while sites with taller vegetation or more blooming flowers had greater species richness but lower diversity. We found no detectable effect of restoration on bee abundance, richness, diversity, or composition. Species composition at native sites differed from those in actively and passively restored sites, which did not differ from each other. Restored sites also had fewer flowers and differing floral composition relative to native sites. These results suggest that if grassland restoration is to benefit bees, efforts should focus on both expanding floral resources and enhancing variables that influence nesting habitat.  相似文献   

9.
Bees are the primary pollinators of flowering plants in almost all ecosystems. Worldwide declines in bee populations have raised awareness about the importance of their ecological role in maintaining ecosystem functioning. The naturally strong philopatric behavior that some bee species show can be detrimental to population viability through increased probability of inbreeding. Furthermore, bee populations found in human-altered landscapes, such as urban areas, can experience lower levels of gene flow and effective population sizes, increasing potential for inbreeding depression in wild bee populations. In this study, we investigated the fine-scale population structure of the solitary bee Colletes inaequalis in an urbanized landscape. First, we developed a predictive spatial model to detect suitable nesting habitat for this ground nesting bee and to inform our field search for nests. We genotyped 18 microsatellites in 548 female individuals collected from nest aggregations throughout the study area. Genetic relatedness estimates revealed that genetic similarity among individuals was slightly greater within nest aggregations than among randomly chosen individuals. However, genetic structure among nest aggregations was low (Nei’s GST = 0.011). Reconstruction of parental genotypes revealed greater genetic relatedness among females than among males within nest aggregations, suggesting male-mediated dispersal as a potentially important mechanism of population connectivity and inbreeding avoidance. Size of nesting patch was positively correlated with effective population size, but not with other estimators of genetic diversity. We detected a positive trend between geographic distance and genetic differentiation between nest aggregations. Our landscape genetic models suggest that increased urbanization is likely associated with higher levels of inbreeding. Overall, these findings emphasize the importance of density and distribution of suitable nesting patches for enhancing bee population abundance and connectivity in human dominated habitats and highlights the critical contribution of landscape genetic studies for enhanced conservation and management of native pollinators.  相似文献   

10.
Inter‐specific interactions are important drivers and maintainers of biodiversity. Compared to trophic and competitive interactions, the role of non‐trophic facilitation among species has received less attention. Cavity‐nesting bees nest in old beetle borings in dead wood, with restricted diameters corresponding to the body size of the bee species. The aim of this study was to test the hypothesis that the functional diversity of cavity‐producing wood boring beetles ‐ in terms of cavity diameters ‐ drives the size diversity of cavity‐nesting bees. The invertebrate communities were sampled in 30 sites, located in forested landscapes along an elevational gradient. We regressed the species richness and abundance of cavity nesting bees against the species richness and abundance of wood boring beetles, non‐wood boring beetles and elevation. The proportion of cavity nesting bees in bee species assemblage was regressed against the species richness and abundance of wood boring beetles. We also tested the relationships between the size diversity of cavity nesting bees and wood boring beetles. The species richness and abundance of cavity nesting bees increased with the species richness and abundance of wood boring beetles. No such relationship was found for non‐wood boring beetles. The abundance of wood boring beetles was also related to an increased proportion of cavity nesting bee individuals. Moreover, the size diversity of cavity‐nesting bees increased with the functional diversity of wood boring beetles. Specifically, the mean and dispersion of bee body sizes increased with the functional dispersion of large wood boring beetles. The positive relationships between cavity producing bees and cavity nesting bees suggest that non‐trophic facilitative interactions between species assemblages play important roles in organizing bee species assemblages. Considering a community‐wide approach may therefore be required if we are to successfully understand and conserve wild bee species assemblages in forested landscapes.  相似文献   

11.
As most stingless bee species depend on preexisting cavities, principally tree hollows, nesting site availability may represent an important restriction in the structuring of their forest communities. The present study examined the spatial dynamics of stingless bee communities in an area of Atlantic Forest by evaluating their swarming to trap-nests. The field work was performed in the Michelin Ecological Reserve (MER) on the southeastern coast of the state of Bahia, Brazil. Seven hundred and twenty trap-nests were distributed within two forest habitats in advanced and initial stages of regeneration. The trap-nests were monitored between September 2009 and March 2011. Twenty-five trap-nests were occupied by five bee species, resulting in a capture ratio of 0.035 swarms/trap (approximately 0.14 swarms/ha), corresponding to 10 swarms/year (0.056 swarms/ha/year). According to previous study at MER, the most abundant species in natural nests were also the most common in trap-nests in the two forest habitats examined, with the exception of Melipona scutellaris Latreille. Swarms of higher numbers of species were captured in initial regeneration stage forests than in advanced regeneration stage areas, and differences in species compositions were significant between both habitats (p?=?0.03); these apparent differences were not consistent, however, when considering richness (p?=?0.14) and total abundance (p?=?0.08). The present study suggests the existence of a minimum cavity size threshold of approximately 1 L for most local species of stingless bees and sustains the hypothesis of a mass effect of Tetragonisca angustula Latreille populations from surrounding disturbed habitats on the MER forest community in terms of propagule (swarm) pressure. Examining swarm densities with trap-nests can be a promising technique for comparative analyses of the carrying capacities of forest habitats for stingless bee colonies, as long as size thresholds of cavities for nesting are taken into consideration.  相似文献   

12.
Anthropogenic disturbances have caused pollinator decline by affecting the abundance and diversity of foraging plants. Anthropogenic disturbances are also thought to drive pollinator decline by reducing nest site availability, but the exact mechanisms by which human activities influence nest site availability are not currently well understood. In this study, we investigated nesting site preference of underground bee Andrena camellia Wu in two orchards. Principal component analysis of environmental factors (bulk density, penetration resistance, water content and temperature) indicated that A. camellia preferred loose, moist and low‐temperature habitats. The favored habitats were located at the bases of the foothills a long distance from human settlements. At the bases, favored nesting substrates decreased along the distance gradient, and nest densities of digger bees increased along the distance gradient. On the summit, however, nesting substrates were compacted, dried with high temperature regardless of distance from human settlements, and the nest densities were all low along the distance gradient. In summary, anthropogenic soil disturbances in the vicinity of human settlements threaten digger bees by altering soil characteristics. The conservation of the soil substrates is addressed in terms of its role in governing the population of digger bee A. camellia.  相似文献   

13.
Restored habitats require long-term management to maintain biodiversity and ensure ecosystem functions. Management strategies are often developed for plant communities, including through seeding and disturbance management, but these actions are taken with a focus on plant dynamics and with little knowledge of the effects on non-plant organisms. Wild bees are often expected to respond to such management actions via their effects on local floral resource availability, but management may also affect bees by altering survival and nesting independently of plant community responses. Working in restoration plantings within a large, actively managed tallgrass prairie preserve, we separated the effects of management and landscape context on bee community abundance and richness from the effects of these covariates on bees mediated through the abundance and richness of the local flowering plant community. We found that bees responded primarily to disturbance management (via bison) and the amount of prairie and forest habitat in the landscape, indicating that across landscapes with relatively abundant flowers and nest-sites, these landscape-level resources are more important than local floral resources for structuring bee communities. In contrast, floral communities responded to restoration age and prescribed burning. Because bees respond to different factors and at a different landscape scale than local plant communities, we conclude that management designed for plants is not sufficient for pollinators. Landscape level restoration may therefore require targeted habitat design and management to successfully restore functionally important animals.  相似文献   

14.
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.  相似文献   

15.
1. Bird nests are ubiquitous but patchy resources in many terrestrial habitats. Nests can support diverse communities of commensal invertebrates, especially moths (Lepidoptera). However, there is a shortage of information on the moths associated with bird nests, and the factors influencing their abundance, diversity and composition. 2. Two hundred and twenty‐four nests, from 16 bird species, were sampled from sites in mid‐Wales (UK) and the moths that emerged from them were recorded. 3. Seventy eight percent of nests produced moths, with 4657 individuals of ten species recorded. Moth communities were dominated by generalist species rather than bird nest specialists. 4. Open nests built in undergrowth supported significantly fewer moths than nests in enclosed spaces (for example, nesting boxes). The occurrence of fleas was positively associated with the incidence and abundance of moths. There was no evidence that different nest types supported different moth communities.  相似文献   

16.
A major challenge in habitat restoration is targeting the key aspects of a species' niche for enhancement, particularly for species that use a diverse set of habitat features. However, restoration that focuses on limited aspects of a species' niche may neglect other resources that are critical to population persistence. We evaluated the ability of native plant hedgerows, planted to increase pollen and nectar resources for wild bees in agricultural landscapes, to provide suitable nesting habitat and enhance nesting rates of ground‐nesting bees. We found that, when compared to unmanaged field edges (controls), hedgerows did not augment most indicators of nest habitat quality (bare ground, soil surface irregularity, and soil hardness), although coarser soils were associated with higher incidence and richness of nesting bees. Hedgerows did not augment nesting rates when compared to control edges. Although all the bee species we detected nesting were also found foraging on floral resources, the foraging versus nesting assemblages found within a site were highly dissimilar. These results may reflect sampling error; or, species found foraging but not nesting in hedgerows could be utilizing hedgerows as “partial habitats,” nesting outside hedgerow plantings but foraging on the floral resources they provide. We conclude that although hedgerows are known to provide critical floral resources to wild bees especially in resource‐poor intensive agricultural landscapes, simply increasing vegetative diversity and structure may not be simultaneously enhancing nesting habitat for ground‐nesting bees.  相似文献   

17.
Many factors drive the organization of communities including environmental factors, dispersal abilities, and competition. In particular, ant communities have high levels of interspecific competition and dominance that may affect community assembly processes. We used a combination of surveys and nest supplementation experiments to examine effects of a dominant ground‐nesting ant (Pheidole synanthropica) on (1) arboreal twig‐nesting, (2) ground‐foraging, and (3) coffee‐foraging ant communities in coffee agroecosystems. We surveyed these communities in high‐ and low‐density areas of P. synanthropica over 2 years. To test for effects on twig ant recruitment, we placed artificial nesting resources on coffee plants in areas with and without P. synanthropica. The first sampling period revealed differences in ant species composition on the ground, in coffee plants, and artificial nests between high‐ and low‐density sites of P. synanthropica. High‐density sites also had significantly lower recruitment of twig ants and had species‐specific effects on twig ant species. Prior to the second survey period, abundance of P. synanthropica declined in the high‐density sites, such that P. synanthropica densities no longer differed. Subsequent sampling revealed no difference in total recruitment of twig ants to artificial nests between treatments. Likewise, surveys of ground and coffee ants no longer showed significant differences in community composition. The results from the first experimental period, followed by survey results after the decline in P. synanthropica densities suggest that dominant ants can drive community assembly via both recruitment and establishment of colonies within the community.  相似文献   

18.
Little is known about the natural history of wild honey bee (Apis mellifera) colonies in the Eastern Cape Province of South Africa. The goal of this research was to examine nest site characteristics of honey bee (A. m. capensis/A. m. scutellata hybrid) colonies sampled from a variety of habitats (nature reserves, livestock farms, and an urban setting) in the Eastern Cape. We also determined how nest site location related to various colony strength parameters. In general, colonies not nesting in ground cavities tended to nest in locations >6 m high when nesting in cliffs and buildings and >2 m high when nesting in trees. Colonies typically nested in cavities whose entrances faced a southeasterly direction and were ~40 L in volume. We sampled a subset of colonies to determine the relationship between nest type and the following colony strength parameters: total area of comb in the colony, the volume of stored honey, pollen, and brood, adult bee population, the weight per adult bee, and the bee/nest cavity volume ratio. In general, colonies nesting in cliffs tended to be stronger than those nesting in the ground or trees. Our findings provide new insights into the nesting biology of honey bees in the Eastern Cape, South Africa, perhaps leading to the formation of conservation recommendations for honey bees in this region.  相似文献   

19.
Pollination is a key ecosystem service, and appropriate management, particularly in agricultural systems, is essential to maintain a diversity of pollinator guilds. However, management recommendations frequently focus on maintaining plant communities, with the assumption that associated invertebrate populations will be sustained. We tested whether plant community, flower resources, and soil moisture would influence hoverfly (Syrphidae) abundance and species richness in floristically‐rich seminatural and floristically impoverished agricultural grassland communities in Wales (U.K.) and compared these to two Hymenoptera genera, Bombus, and Lasioglossum. Interactions between environmental variables were tested using generalized linear modeling, and hoverfly community composition examined using canonical correspondence analysis. There was no difference in hoverfly abundance, species richness, or bee abundance, between grassland types. There was a positive association between hoverfly abundance, species richness, and flower abundance in unimproved grasslands. However, this was not evident in agriculturally improved grassland, possibly reflecting intrinsically low flower resource in these habitats, or the presence of plant species with low or relatively inaccessible nectar resources. There was no association between soil moisture content and hoverfly abundance or species richness. Hoverfly community composition was influenced by agricultural improvement and the amount of flower resource. Hoverfly species with semiaquatic larvae were associated with both seminatural and agricultural wet grasslands, possibly because of localized larval habitat. Despite the absence of differences in hoverfly abundance and species richness, distinct hoverfly communities are associated with marshy grasslands, agriculturally improved marshy grasslands, and unimproved dry grasslands, but not with improved dry grasslands. Grassland plant community cannot be used as a proxy for pollinator community. Management of grasslands should aim to maximize the pollinator feeding resource, as well as maintain plant communities. Retaining waterlogged ground may enhance the number of hoverflies with semiaquatic larvae.  相似文献   

20.
Anthropogenic landscapes are associated with biodiversity loss and large shifts in species composition and traits. These changes predict the identities of winners and losers of future global change, and also reveal which environmental variables drive a taxon's response to land use change. We explored how the biodiversity of native bee species changes across forested, agricultural, and urban landscapes. We collected bee community data from 36 sites across a 75,000 km2 region, and analyzed bee abundance, species richness, composition, and life‐history traits. Season‐long bee abundance and richness were not detectably different between natural and anthropogenic landscapes, but community phenologies differed strongly, with an early spring peak followed by decline in forests, and a more extended summer season in agricultural and urban habitats. Bee community composition differed significantly between all three land use types, as did phylogenetic composition. Anthropogenic land use had negative effects on the persistence of several life‐history strategies, including early spring flight season and brood parasitism, which may indicate adaptation to conditions in forest habitat. Overall, anthropogenic communities are not diminished subsets of contemporary natural communities. Rather, forest species do not persist in anthropogenic habitats, but are replaced by different native species and phylogenetic lineages preadapted to open habitats. Characterizing compositional and functional differences is crucial for understanding land use as a global change driver across large regional scales.  相似文献   

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