Plantation vs. natural forest: matrix quality determines pollinator abundance in crop fields

The impact of landscape structure on pesticide exposure to honey bees

Pesticides may have serious negative impacts on bee populations. The pesticide exposure of bees could depend on the surrounding landscapes in which they forage. In this study, we assess pesticide exposure across various land-use categories, while targeting the Japanese honey bee, Apis cerana japonica, a native subspecies of the eastern honey bee. In a project involving public participation, we measured the concentrations of major pesticides in honey and beeswax collected from 175 Japanese honey bee colonies across Japan and quantitatively analyzed the relationships between pesticide presence/absence or pesticide concentration and land-use categories around the colonies. Our findings revealed that the surrounding environment in which bees live strongly influences pesticide residues in beehive materials, whether the pesticides are systemic or not, with a clear trend for each land-use category. Agricultural lands, particularly paddy fields and orchards, and urban areas resulted in higher pesticide exposure, whereas forests presented a lower risk of exposure. To effectively control pesticide exposure levels in bees, it is essential to understand pesticide usage patterns and to develop appropriate regulatory systems in non-agricultural lands, similar to those in agricultural lands.

Dominance of non-wetland-dependent pollinators in a plant community in a small natural wetland in Shimane, Japan

Many wetland plants rely on insects for pollination. However, studies examining pollinator communities in wetlands remain limited. Some studies conducted in large wetlands (> 10 ha) have suggested that wetland-dependent flies, which spend their larval stage in aquatic and semi-aquatic habitats, dominate as pollinators. However, smaller wetlands surrounded by secondary forests are more prevalent in Japan, in which pollinators from the surrounding environment might be important. Additionally, information regarding floral traits that attract specific pollinator groups in wetland communities is scarce. Therefore, this study aimed to understand the characteristics of insect pollinators in a small natural wetland (2.5 ha) in Japan. We examined the major pollinator groups visiting 34 plant species and explored the relationship between the flower visitation frequency of each pollinator group and floral traits. Overall, flies were the most dominant pollinators (42%), followed by bees and wasps (33%). Cluster analysis indicated that fly-dominated plants were the most abundant among 14 of the 34 target plant species. However, 85% of the hoverflies, the most abundant flies, and 82% of the bees were non-wetland-dependent species, suggesting that these terrestrial species likely originated from the surrounding environment. Therefore, pollinators from the surrounding environment would be important in small natural wetlands. Flies tend to visit open and white/yellow flowers, whereas bees tended to visit tube-shaped flowers, as in forest and grassland ecosystems. The dominance of flies in small wetlands would be due to the dominance of flowers preferred by flies (e.g., yellow/white flowers) rather than because of their larval habitats.

Comparison of RNA-Seq analysis data between tracheal mite-infested and uninfested Japanese honey bees (Apis cerana japonica)

OBJECTIVE

The purpose of this data set is to investigate differences in RNA-Seq transcriptome profiles between Acarapis woodi-infested and uninfested Japanese honey bees (Apis cerana japonica). The data set is strengthened by data collected from different body parts (head, thorax, and abdomen). The data set will support future studies of molecular biological changes in mite-infested honey bees.

DATA DESCRIPTION

We collected 5 mite-infested and 5 uninfested A. cerana japonica workers from each of 3 different colonies (designated as A, B, and C). Workers were dissected into 3 body sites (i.e., heads, thoraces, and abdomen), and 5 of each body site were pooled together for RNA extraction, generating a total of 18 RNA-Seq samples (2 infection status × 3 colonies × 3 body sites). FASTQ data files of each sample that were generated by a DNBSEQ-G400 sequencer with the 2 × 100 bp paired-end sequencing protocol are available in the DDBJ Sequence Read Archive under accession number DRA015087 (RUN: DRR415616-DRR415633, BioProject: PRJDB14726, BioSample: SAMD00554139-SAMD00554156, Experiment: DRX401183-DRX401200). The data set is a fine-scale analysis of gene expression in the mite-infested A. cerana japonica workers because 18 RNA-Seq samples are separated by 3 body sites.

Characterization of the RACK1 gene of Aips cerana cerana and its role in adverse environmental stresses

Receptors for Activated C Kinase 1 (RACK1s) are a kind of multifunction scaffold protein that plays an important role in cell signal transductions and animal development. However, the function of RACK1 in the Chinese honeybee Apis cerana cerana is little known. Here, we isolated and identified a RACK1 gene from Apis cerana cerana, named AccRACK1. By bioinformatic analysis, we revealed a high nucleic acid homology between AccRACK1 and RACK1 of Apis cerana. RT-qPCR analyses demonstrated AccRACK1 was mostly expressed in 3rd instar larvae, darked-eyed pupae and adults (one and thirty days post-emergence), suggesting it might participate in the development of A. cerana cerana. Moreover, the expression of AccRACK1 was highest in the thorax, followed by the venom gland. Compared to the blank control group, AccRACK1 was induced by 24 and 44 °C, HgCl2 and pesticides (paraquat, pyridaben and methomyl) but inhibited by 14 °C, H2O2, UV light and cyhalothrin. Additionally, 0.05, 0.1, 1, 5 and 10 mg/ml PPN (juvenile hormone analogue pyriproxyfen) could promote the expression of AccRACK1, with 1 mg/ml showing the highest upregulation, suggesting it was regulated by hormones. Further study found that after knockdown of AccRACK1 by RNAi, the expression of the eukaryotic initiation factor 6 of A. cerana cerana (AcceIF6), an initiation factor regulating the initiation of translation, was inhibited, indicating AccRACK1 might affect cellular responses by translation. These findings, taken together, suggest AccRACK1 is involved in the development and responses to abiotic stresses of A. cerana cerana, and therefore, it may be of critical importance to the survival of A. cerana cerana.

Understory Vegetation Dynamics across a Poplar Plantation Chronosequence in Reclaimed Coastal Saline Soil

Although the understory vegetation abundance, diversity, and composition associated with stand development in natural forests have been well reported, only a few studies have examined the age-related changes of understory vegetation in fast-growing planted forests in reclaimed soils. This study measured the understory vegetation and soil variables in 8-, 12-, and 18-year-old poplar plantations in reclaimed coastal saline soil of Eastern China. This study examined how the abundance, diversity, and composition changed with stand development and the soil variables. Further, structural equation modeling (SEM) was used to evaluate the direct and indirect factors influencing the abundance and plant diversity throughout stand development. Herb abundance was significantly higher in the youngest and oldest stands, whereas shrub abundance was higher in the middle-aged stands. Shannon’s diversity index was significantly higher in the youngest stand for herbs, whereas it was highest in the middle-aged stands for shrubs. A multivariate analysis revealed that the herb and shrub composition were influenced by the stand age, total soil carbon and soil pH. The most parsimonious SEM model showed the negative direct effects of the stand age and the negative indirect effects of the stand age via the soil variables on shrub abundance, shrub diversity, and herb diversity, suggesting that the increase of overstory biomass with the stand age reduces resources available for the understory. Our results revealed that understory diversity and composition might change with stand development mediated by the changes in understory light and soil resources in fast-growing plantations.

Impacts of forestry on boreal forests: An ecosystem services perspective

Forests are widely recognized as major providers of ecosystem services, including timber, other forest products, recreation, regulation of water, soil and air quality, and climate change mitigation. Extensive tracts of boreal forests are actively managed for timber production, but actions aimed at increasing timber yields also affect other forest functions and services. Here, we present an overview of the environmental impacts of forest management from the perspective of ecosystem services. We show how prevailing forestry practices may have substantial but diverse effects on the various ecosystem services provided by boreal forests. Several aspects of these processes remain poorly known and warrant a greater role in future studies, including the role of community structure. Conflicts among different interests related to boreal forests are most likely to occur, but the concept of ecosystem services may provide a useful framework for identifying and resolving these conflicts.

Potential supply of floral resources to managed honey bees in natural mistbelt forests

Honey bees play a vital role in the pollination of flowers in many agricultural systems, while providing honey through well managed beekeeping activities. Managed honey bees rely on the provision of pollen and nectar for their survival and productivity. Using data from field plot inventories in natural mistbelt forests, we (1) assessed the diversity and relative importance of honey bee plants, (2) explored the temporal availability of honey bee forage (nectar and pollen resources), and (3) elucidated how plant diversity (bee plant richness and overall plant richness) influenced the amount of forage available (production). A forage value index was defined on the basis of species-specific nectar and pollen values, and expected flowering period. Up to 50% of the overall woody plant richness were found to be honey bee plant species, with varying flowering period. As expected, bee plant richness increased with overall plant richness. Interestingly, bee plants' flowering period was spread widely over a year, although the highest potential of forage supply was observed during the last quarter. We also found that only few honey bee plant species contributed 90 percent of the available forage. Surprisingly, overall plant richness did not significantly influence the bee forage value. Rather, bee plant species richness showed significant and greater effect. The results of this study suggest that mistbelt forests can contribute to increase the spatial and temporal availability of diverse floral resources for managed honey bees. Conservation efforts must be specifically oriented towards honey bee plant species in mistbelt forests to preserve and enhance their potential to help maintain honey bee colonies. The implications for forest management, beekeeping activities and pollination-based agriculture were discussed.

Genetic Structure and Potential Environmental Determinants of Local Genetic Diversity in Japanese Honeybees (Apis cerana japonica)

Declines in honeybee populations have been a recent concern. Although causes of the declines remain unclear, environmental factors may be responsible. We focused on the potential environmental determinants of local populations of wild honeybees, Apis cerana japonica, in Japan. This subspecies has little genetic variation in terms of its mitochondrial DNA sequences, and genetic variations at nuclear loci are as yet unknown. We estimated the genetic structure and environmental determinants of local genetic diversity in nuclear microsatellite genotypes of fathers and mothers, inferred from workers collected at 139 sites. The genotypes of fathers and mothers showed weak isolation by distance and negligible genetic structure. The local genetic diversity was high in central Japan, decreasing toward the peripheries, and depended on the climate and land use characteristics of the sites. The local genetic diversity decreased as the annual precipitation increased, and increased as the proportion of urban and paddy field areas increased. Positive effects of natural forest area, which have also been observed in terms of forager abundance in farms, were not detected with respect to the local genetic diversity. The findings suggest that A. cerana japonica forms a single population connected by gene flow in its main distributional range, and that climate and landscape properties potentially affect its local genetic diversity.

Effects of young poplar plantations on understory plant diversity in the Dongting Lake wetlands, China

This study evaluated the effects of young poplar plantations on understory plant diversity in the Dongting Lake wetlands, China. Poplar plantations resulted in a higher species number and Shannon's diversity. Species compositions were different between areas with poplar and reed populations: a lower ratio of hygrophytes but a higher ratio of mesophytes, and a higher ratio of heliophytes but a lower ratio of neutrophilous or shade plants in poplar areas compared to reed areas. Poplar plantations supported a higher ratio of ligneous plants in the entire Dongting Lake area, but there was no difference in the monitored plots. Unlike reedy areas, poplar plantations had higher light availability but lower soil water content during the growing seasons. These data suggest that young poplar plantations generally increased species richness and plant diversity, but significantly changed species composition due to the reduced soil water and increased light availability.

Succession influences wild bees in a temperate forest landscape: the value of early successional stages in naturally regenerated and planted forests

In many temperate terrestrial forest ecosystems, both natural human disturbances drive the reestablishment of forests. Succession in plant communities, in addition to reforestation following the creation of open sites through harvesting or natural disturbances, can affect forest faunal assemblages. Wild bees perform an important ecosystem function in human-altered and natural or seminatural ecosystems, as they are essential pollinators for both crops and wild flowering plants. To maintain high abundance and species richness for pollination services, it is important to conserve and create seminatural and natural land cover with optimal successional stages for wild bees. We examined the effects of forest succession on wild bees. In particular, we evaluated the importance of early successional stages for bees, which has been suspected but not previously demonstrated. A range of successional stages, between 1 and 178 years old, were examined in naturally regenerated and planted forests. In total 4465 wild bee individuals, representing 113 species, were captured. Results for total bees, solitary bees, and cleptoparasitic bees in both naturally regenerated and planted conifer forests indicated a higher abundance and species richness in the early successional stages. However, higher abundance and species richness of social bees in naturally regenerated forest were observed as the successional stages progressed, whereas the abundance of social bees in conifer planted forest showed a concave-shaped relationship when plotted. The results suggest that early successional stages of both naturally regenerated and conifer planted forest maintain a high abundance and species richness of solitary bees and their cleptoparasitic bees, although social bees respond differently in the early successional stages. This may imply that, in some cases, active forest stand management policies, such as the clear-cutting of planted forests for timber production, would create early successional habitats, leading to significant positive effects for bees in general.