Potential associations between the mite Varroa destructor and other stressors in honeybee colonies (Apis mellifera L.) in temperate and subtropical climate from Argentina

Perspectives on socio-ecological studies in the Northern and Southern Hemispheres

Socio-ecology studies the relationships between human activities and natural systems and their importance in management and public policy. Our objective was to analyse how published papers in countries with a high Human Development Index (HDI) perform socio-ecological studies and compare them between the Northern and Southern Hemispheres. To do this, we used the Scopus platform as a source for searching and obtaining scientific papers about socio-ecological studies conducted in countries from the Northern and Southern Hemispheres. We calculated the number (n) of papers published per year and classified them using the main subject areas of the SCImago Journal & Country Rank database. Then, we analysed whether papers included specific recommendations for natural system management, nature conservation, policies or governance structures, or science in general. Besides, we studied whether the papers addressed socio-ecological studies related to flora and fauna and from what specific group of organisms or systems. Data were compared using the chi-square (χ ²) test (Pearson p < 0.005). A total of 467 papers were analysed, where 34% were from the Southern Hemisphere (mainly Argentina, Australia, Chile, and South Africa) and 66% from the Northern Hemisphere (mainly the USA, Canada, and Spain). The Northern Hemisphere (mainly North America and Europe) played a major role in the socio-ecological knowledge exchange than the Southern Hemisphere (South America and Africa). The results showed socio-ecological studies focused mainly on generating management recommendations in social and environmental science fields. The number of studies coming from the Northern Hemisphere was significantly higher than those from the Southern Hemisphere. Most of them were conducted at a local level (e.g., watersheds or human settlements) in three different systems (i) terrestrial (e.g., forests or grasslands), (ii) freshwater (e.g., rivers or streams) and (iii) marine (e.g., coastlines or seas). Most of the studies (70%) were conducted in production systems, where the majority included livestock (mainly bovine) and aquatic fisheries (e.g., salmon, artisanal coastal fishing, or trout). Most vegetation papers (65%) were on native forests. Papers on wildlife made up 30% of all animal-related studies, with mammals, birds, and marine invertebrates (such as collars) being the most extensively researched species. This work highlighted the socio-ecological approach that was used in the analysed countries with greater HDI to develop management options for natural systems.

Colonisation Patterns of Nosema ceranae in the Azores Archipelago

Nosema ceranae is a highly prevalent pathogen of Apis mellifera, which is distributed worldwide. However, there may still exist isolated areas that remain free of N. ceranae. Herein, we used molecular tools to survey the Azores to detect N. ceranae and unravel its colonisation patterns. To that end, we sampled 474 colonies from eight islands in 2014/2015 and 91 from four islands in 2020. The findings revealed that N. ceranae was not only present but also the dominant species in the Azores. In 2014/2015, N. apis was rare and N. ceranae prevalence varied between 2.7% in São Jorge and 50.7% in Pico. In 2020, N. ceranae prevalence increased significantly (p < 0.001) in Terceira and São Jorge also showing higher infection levels. The spatiotemporal patterns suggest that N. ceranae colonised the archipelago recently, and it rapidly spread across other islands, where at least two independent introductions might have occurred. Flores and Santa Maria have escaped the N. ceranae invasion, and it is remarkable that Santa Maria is also free of Varroa destructor, which makes it one of the last places in Europe where the honey bee remains naive to these two major biotic stressors.

Bee Health and Productivity in Apis mellifera, a Consequence of Multiple Factors

Managed honeybees play an important role as pollinators. The health and nutritional condition of honeybee colonies (Apis mellifera L.) depends for an important part on management practices, and it is influenced by multiple factors. This study aims to identify the stressors that lead to the loss of honeybee health and its consequences on the colony's productivity. Different aspects related to management practices, productivity, clinical observations related to diseases, presence of sanitary gaps in the apiaries, colony strength, weather and infestation rates by Varroa sp. mites were measured. The information was collected during two monitoring in 53 apiaries in the Province of Santa Fe, Argentina. The results show correlations among many of the management practices, health condition and yield. The most important factors affecting the productivity of the studied honeybee colonies were nuclei preparation, the number of combs in the brood chamber, change of bee queen, disinfection of beekeeping material, among other less significant ones. Although honey production is important in the region, the colony strength was deficient and inadequate during both monitoring. Due to its dependence on management by the beekeeper, it is suggested that a holistic approach could improve bee health, increasing the productivity of honeybees.

Morphotype and haplotype identification of Varroa destructor (Acari: Varroidae), and its importance for apiculture in Nicaragua

The ectoparasite Varroa (Acari: Varroidae) is considered to be the main pest of honey bees (Apis mellifera L.) in Nicaragua. The aim of this study was to determine morphotypes and mitochondrial haplotypes of the Varroa mites, related to infestation levels in A. mellifera hives in Nicaragua in a cross-sectional study (2013-2016). Samples were taken from 34 sentinel apiaries in five geographical zones; from 713 Varroa females collected during the study, 153 were selected for measurement of various morphometric characters for further classification into morphotypes. The mitochondrial haplotype was assigned to one of the two (Korean or Japanese), using the restriction by SacI of the PCR product of a fragment of the gene CO-I. Morphometric measurement and sequencing revealed the affiliation to the species Varroa destructor with a mean (± SD) body width of 1699.1 ± 60.2 µm and a body length of 1161.1 ± 34.9 µm. Body characters were significantly different among the 34 apiaries. Varroa destructor samples were classified into four morphotypes, with no significant differences in the geographical zones. As GAGCTC SacI enzyme cleavage sequences were not observed, all PCR products were identified as V. destructor Korean haplotype. The CO-I gene nucleotide sequences from two samples V. destructor showed both 100% similarity with the Korean haplotype and 99.8% similarity to the Japanese haplotype. Although the V. destructor mite was identified as a Korean haplotype, host-parasite association in 2 decades has led into a balance without entering into severe losses in the Nicaraguan apiculture.

Prioritizing changes in management practices associated with reduced winter honey bee colony losses for US beekeepers

Beekeepers attempt to manage their honey bee colonies in ways that optimize colony health. Disentangling the impact of management from other variables affecting colony health is complicated by the diversity of practices used and difficulties handling typically complex and incomplete observational datasets. We propose a method to 1) compress multi-factored management data into a single index, to holistically investigate the real world impact of management on colony mortality, and 2) simplify said index to identify the core practices for which a change in behavior is associated with the greatest improvement in survivorship. Experts scored the practices of US beekeepers (n = 18,971) documented using four years of retrospective surveys (2012-2015). Management Index scores significantly correlated with loss rates, with beekeepers most in line with recommendations suffering lower losses. The highest ranked practices varied by operation type, as recommendations accounted for the current prevalence of practices. These results validate experts' opinion using empirical data, and can help prioritize extension messages. Improving management will not prevent all losses; however, we show that few behavioral changes (in particular related to comb management, sources of new colonies and Varroa management) can lead to a non-negligible reduction in risk.

Impact of Varroa destructor and associated pathologies on the colony collapse disorder affecting honey bees

Varroa mite is the major threat to the western honey bee, Apis mellifera, and the cause of significant economic losses in the apiculture industry. Varroa destructor feeds on brood and adult bees being responsible for vectoring virus infections and other diseases. This study analyses the role of Varroa and other associated pathogens, such as viruses or the fungus Nosema ceranae, and their relationships regarding the viability of the bee colony. It has been carried out during one beekeeping season, with the subspecies A. m. iberiensis, commonly used in the apiculture industry of Spain. Our study shows a significant relationship between the presence of Varroa destructor and viral infection by deformed wing virus and acute bee paralysis virus. Nosema ceranae behaved as an opportunistic pathogen. In addition, this study explored a potential naturally occurring subset of peptides, responsible for the humoral immunity of the bees. The expression of the antimicrobial peptides abaecin and melittin showed a significant relationship with the levels of Varroa mite and the deformed wing virus.

Genetic variation and heteroplasmy of Varroa destructor inferred from ND4 mtDNA sequences

Varroa destructor, a parasitic mite of the western honey bee, Apis mellifera L., is a serious threat to colonies and beekeeping worldwide. Population genetics studies of the mite have provided information on two mitochondrial haplotypes infecting honey bee colonies, named K and J (after Korea and Japan, respectively, where they were originally identified). On the American continent, the K haplotype is much more prevalent, with the J haplotype only detected in some areas of Brazil. The aims of the present study were to assess the genetic diversity of V. destructor populations in the major beekeeping region of Argentina and to evaluate the presence of heteroplasmy at the nucleotide level. Phoretic mites were collected from managed A. mellifera colonies in ten localities, and four mitochondrial DNA (mtDNA) regions (COXI, ND4, ND4L, and ND5) were analyzed. Based on cytochrome oxidase subunit I (COXI) sequencing, exclusively the K haplotype of V. destructor was detected. Furthermore, two sub-haplotypes (KArg-N1 and KArg-N2) were identified from a variation in ND4 sequences and the frequency of these sub-haplotypes was found to significantly correlate with geographical latitude. The occurrence of site heteroplasmy was also evident for this gene. Therefore, ND4 appears to be a sensitive marker for detecting genetic variability in mite populations. Site heteroplasmy emerges as a phenomenon that could be relatively frequent in V. destructor.