Landscape Integrity Eclipses Local Effects of Floral Resource Availability on Bumble Bee (Bombus Spp.) Abundance in a Water-Limited Island Ecosystem

ContextHabitat loss threatens to exacerbate climate change impacts on pollinator communities, particularly in Mediterranean-type ecosystems where late season floral resource availability is limited by seasonal drought. While gardens have been found to supplement floral resources in water-limited urban landscapes, less is known about the role of natural habitat diversity in sustaining late season floral resources in more intact landscapes. ObjectivesWe investigated the importance of habitat integrity and diversity for bumble bees in a water-limited ecosystem, observing bumble bee community response to seasonal drought across gradients of disturbance and soil moisture.MethodsWe applied hierarchical models to estimate the effects of local site conditions versus landscape scale estimates of matrix habitat on bumble bee abundance. Floral resources, soil moisture, and other environmental variables were sampled along randomly distributed belt transects. Geospatial estimates of matrix habitat were derived from terrestrial ecosystem data. Bumble bees were sampled with blue vane traps.ResultsIn the late season we found that modified wet areas supported more floral resources and bumble bee workers as compared to dry semi-natural environments. Wetlands also supported more late season floral resources and bumble bee workers, though the latter effect was not significant. Despite higher levels of late season floral resources in modified wet environments, modified matrix habitat was negatively associated, and natural matrix positively associated, with workers in June and late-flying queens in July and August. We also detected differences in bumble bee community composition in disturbed versus undisturbed environments.ConclusionsThough wet modified habitats sustained the highest levels of late season floral resource availability and worker abundances in our study, bumble bee diversity and abundance were limited primarily by the availability of natural matrix habitat at the landscape scale. The conservation of natural habitat integrity and diversity can help support critical nesting and foraging habitat, and should be prioritized in efforts to foster the resilience of pollinator communities.

The queen, but not the brood, drives early changes in brain gene expression in bumble bee workers

Worker reproduction in social insects is often regulated by the queen, but can be regulated by the brood and nestmates, who may use different mechanisms to induce the same outcomes in subordinates. Analysis of brain gene expression patterns in bumble bee workers (Bombus impatiens) in response to the presence of the queen, the brood, both or neither, identified 18 differentially expressed genes, 17 of them are regulated by the queen and none are regulated by the brood. Overall, brain gene expression differences in workers were driven by the queen’s presence, despite recent studies showing that brood reduces worker egg laying and provides context to the queen pheromones. The queen affected important regulators of reproduction and brood care across insects, such as neuroparsin and vitellogenin, and a comparison with similar datasets in the honey bee and the clonal raider ant revealed that neuroparsin is differentially expressed in all species. These data emphasize the prominent role of the queen in regulating worker physiology and behavior. Genes that serve as key regulators of workers’ reproduction are likely to play an important role in the evolution of sociality.

The distribution and population dynamics of the honey bee pathogens Crithidia mellificae and Lotmaria passim in New Zealand

<p>The honey bee Apis mellifera is experiencing colony losses across the world, this is not the first time in history colony losses have been reported. New molecular detection methods such as real-time PCR allow the detection and analysis of pathogens present in colonies, quickly and reliably. Of the pathogens that the honey bee is host to, trypanosomes are one of the least understood and trypanosome interactions within the honey bee host remain largely unknown. Using the bumble bee as a model for this host-parasite relationship. The trypanosome C. bombi is known to cause a reduced ability to gain nutrients from food and an overall decrease in efficiency of queens in founding colonies in spring. These negative correlations are significant enough in the bumble bee to warrant investigation into trypanosomes in the honey bee. The trypanosome C. mellificae was first described in the honey bee in 1967. A screening study in 2009 included a test for and detected the trypanosome in modern honey bee samples. In 2013 C. mellificae was identified as a contributory factor to overwintering colony losses when co-infected with N. ceranae. Following studies detected trypanosomes and led to the characterisation of a new species, L. passim in 2013. Lotmaria passim was first detected in New Zealand in 2014 however no subsequent studies had been undertaken to identify the distribution and dynamics of trypanosomes in New Zealand honey bee colonies. My goal in this study was to identify the presence of trypanosomes in New Zealand. In an overview study of 47 honey bee colonies from across New Zealand, 46 were positive for the L. passim species. Identified by sequencing of the GAPDH gene. A yearlong study of 15 colonies revealed that the infection rate of L. passim was consistent throughout the year and very low genetic variation was detected. Lotmaria passim was detected in all parts of New Zealand sampled in this study and often in high levels. A positive correlation was detected when L. passim was present in addition to N. apis. There was no detection of C. mellificae in my study. The lack of detection of C. mellificae may suggest that the species is not present, or that it is in such low levels it cannot yet be detected. In parallel to this trypanosome study two Nosema spp. and DWV were also examined. Nosema apis was found to be more prevalent than N. ceranae, which was not present in any South Island samples. A strong positive correlation was detected between the two Nosema spp. DWV showed a high level of variation likely a reflection of differing Varroa management practices in apiaries in this study. This study of trypanosomes is the first of its kind in New Zealand identifying the presence and population dynamics of L. passim. This in conjunction with data on Nosema spp. and DWV will be of value to the New Zealand apiculture industry and contribute to global honey bee health studies.</p>

The distribution and population dynamics of the honey bee pathogens Crithidia mellificae and Lotmaria passim in New Zealand

<p>The honey bee Apis mellifera is experiencing colony losses across the world, this is not the first time in history colony losses have been reported. New molecular detection methods such as real-time PCR allow the detection and analysis of pathogens present in colonies, quickly and reliably. Of the pathogens that the honey bee is host to, trypanosomes are one of the least understood and trypanosome interactions within the honey bee host remain largely unknown. Using the bumble bee as a model for this host-parasite relationship. The trypanosome C. bombi is known to cause a reduced ability to gain nutrients from food and an overall decrease in efficiency of queens in founding colonies in spring. These negative correlations are significant enough in the bumble bee to warrant investigation into trypanosomes in the honey bee. The trypanosome C. mellificae was first described in the honey bee in 1967. A screening study in 2009 included a test for and detected the trypanosome in modern honey bee samples. In 2013 C. mellificae was identified as a contributory factor to overwintering colony losses when co-infected with N. ceranae. Following studies detected trypanosomes and led to the characterisation of a new species, L. passim in 2013. Lotmaria passim was first detected in New Zealand in 2014 however no subsequent studies had been undertaken to identify the distribution and dynamics of trypanosomes in New Zealand honey bee colonies. My goal in this study was to identify the presence of trypanosomes in New Zealand. In an overview study of 47 honey bee colonies from across New Zealand, 46 were positive for the L. passim species. Identified by sequencing of the GAPDH gene. A yearlong study of 15 colonies revealed that the infection rate of L. passim was consistent throughout the year and very low genetic variation was detected. Lotmaria passim was detected in all parts of New Zealand sampled in this study and often in high levels. A positive correlation was detected when L. passim was present in addition to N. apis. There was no detection of C. mellificae in my study. The lack of detection of C. mellificae may suggest that the species is not present, or that it is in such low levels it cannot yet be detected. In parallel to this trypanosome study two Nosema spp. and DWV were also examined. Nosema apis was found to be more prevalent than N. ceranae, which was not present in any South Island samples. A strong positive correlation was detected between the two Nosema spp. DWV showed a high level of variation likely a reflection of differing Varroa management practices in apiaries in this study. This study of trypanosomes is the first of its kind in New Zealand identifying the presence and population dynamics of L. passim. This in conjunction with data on Nosema spp. and DWV will be of value to the New Zealand apiculture industry and contribute to global honey bee health studies.</p>

The queen, but not the brood, drives brain gene expression in bumble bee workers

Worker reproduction in social insects is often regulated by the queen, but can be regulated by the brood and nestmates, who may use different mechanisms to induce the same outcomes in subordinates. Analysis of brain gene expression patterns in bumble bee workers (Bombus impatiens) in response to the presence of the queen, the brood, both or neither, identified 18 differentially expressed genes, 17 of them are regulated by the queen and none are regulated by the brood. Overall, brain gene expression differences in workers were driven by the queen’s presence, despite recent studies showing that brood reduces worker egg laying and provides context to the queen pheromones. The queen affected important regulators of reproduction and brood care across insects, such as neuroparsin and vitellogenin, and a comparison with similar datasets in the honeybee and the raider ant revealed that neuroparsin is differentially expressed in all species. These data emphasize the prominent role of the queen in regulating worker physiology and behavior, and the need to consider components other than the queen when examining regulators of worker sterility. Genes that serve as key regulators of workers’ reproduction are likely to play an important role in the evolution of sociality.