Juliana Rangel

Encuesta nacional sobre la pérdida anual de colmenas de abejas manejadas durante 2014–2015 en los EEUU

Declines of pollinators and high mortality rates of honey bee colonies are a major concern, both in the USA and globally. Long-term data on summer, winter, and annual colony losses improve our understanding of forces shaping the viability of the pollination industry. Since the mass die-offs of colonies in the USA during the winter of 2006–2007, generally termed “Colony Collapse Disorder” (CCD), annual colony loss surveys have been conducted. These surveys gage colony losses among beekeepers of all operation sizes, recruited to participate via regional beekeeping organizations, phone calls, and postal mail. In the last three years, these surveys include summer and annual losses in addition to winter losses. Winter losses in this most recent survey include 5,937 valid participants (5,690 backyard, 169 sideline, and 78 commercial beekeepers), collectively managing 414,267 colonies on 1 October 2014 and constituting 15.1% of the estimated 2.74 million managed colonies in the USA. Annual losses are typically higher than either winter or summer losses, as they calculate losses over the entire year. Total reported losses were 25.3% [95% CI 24.7–25.9%] over the summer, 22.3% [95% CI 21.9–22.8%] over the winter, and 40.6% [95% CI 40.0–41.2%] for the entire 2014–2015 beekeeping year. Average losses were 14.7% [95% CI 14.0–15.3%] over the summer, 43.7% [95% CI 42.8–44.6%] over the winter, and 49.0% [95% CI 48.1–50.0%] over the entire year. While total winter losses were lower in 2014–2015 than in previous years, summer losses remained high, resulting in total annual colony losses of more than 40% during the survey period. This was the first year that total losses were higher in the summer than in the winter, explained in large part by commercial beekeepers reporting losses of 26.2% of their managed colonies during summer, compared to 20.5% during winter. Self-identified causes of overwintering mortality differed by operation size, with smaller backyard beekeepers generally indicating colony management issues (e.g., starvation, weak colony in the fall), in contrast to commercial beekeepers who typically emphasize parasites or factors outside their control (e.g., varroa, nosema, queen failure). More than two-thirds of all beekeepers (67.3%) had higher colony losses than they deemed acceptable.

Colony fissioning in honey bees: size and significance of the swarm fraction

During colony founding in honey bees, a portion of a colony’s workforce (the “swarm fraction”) departs with the old mother queen in a swarm while the remaining workforce stays with a new daughter queen in the parental nest. There is little quantitative information about swarm fraction size and about how swarm fraction size affects the growth and survival of mother-queen and daughter-queen colonies. We measured (a) the swarm fraction in naturally fissioning honey bee colonies, (b) the growth and survival of mother-queen colonies as a function of swarm size, and (c) the growth and survival of mother-queen and daughter-queen colonies as a function of the swarm fraction. We found an average swarm fraction of 0.75. We also found a significant positive effect of swarm size and swarm fraction on the growth (i.e., comb built, brood produced, food stored, and weight gained) and the survival of mother-queen colonies. We found no effect of swarm fraction on the survival of daughter-queen colonies. Evidently, a honey bee colony must devote a large majority of its workforce to a swarm so that the mother-queen colony can grow sufficiently rapidly to survive its first winter.

No intracolonial nepotism during colony fissioning in honey bees

Most species of social insects have singly mated queens, but in some species each queen mates with numerous males to create a colony whose workers belong to multiple patrilines. This colony genetic structure creates a potential for intracolonial nepotism. One context with great potential for such nepotism arises in species, like honey bees, whose colonies reproduce by fissioning. During fissioning, workers might nepotistically choose between serving a young (sister) queen or the old (mother) queen, preferring the former if she is a full-sister but the latter if the young queen is only a half-sister. We examined three honeybee colonies that swarmed, and performed paternity analyses on the young (immature) queens and samples of workers who either stayed with the young queens in the nest or left with the mother queen in the swarm. For each colony, we checked whether patrilines represented by immature queens had higher proportions of staying workers than patrilines not represented by immature queens. We found no evidence of this. The absence of intracolonial nepotism during colony fissioning could be because the workers cannot discriminate between full-sister and half-sister queens when they are immature, or because the costs of behaving nepotistically outweigh the benefits.

Africanization of a feral honey bee (Apis mellifera) population in South Texas: does a decade make a difference?

Abstract The arrival to the United States of the Africanized honey bee, a hybrid between European subspecies and the African subspecies Apis mellifera scutellata, is a remarkable model for the study of biological invasions. This immigration has created an opportunity to study the dynamics of secondary contact of honey bee subspecies from African and European lineages in a feral population in South Texas. An 11‐year survey of this population (1991–2001) showed that mitochondrial haplotype frequencies changed drastically over time from a resident population of eastern and western European maternal ancestry, to a population dominated by the African haplotype. A subsequent study of the nuclear genome showed that the Africanization process included bidirectional gene flow between European and Africanized honey bees, giving rise to a new panmictic mixture of A. m. scutellata‐ and European‐derived genes. In this study, we examined gene flow patterns in the same population 23 years after the first hybridization event occurred. We found 28 active colonies inhabiting 92 tree cavities surveyed in a 5.14 km2 area, resulting in a colony density of 5.4 colonies/km2. Of these 28 colonies, 25 were of A. m. scutellata maternal ancestry, and three were of western European maternal ancestry. No colonies of eastern European maternal ancestry were detected, although they were present in the earlier samples. Nuclear DNA revealed little change in the introgression of A. m. scutellata‐derived genes into the population compared to previous surveys. Our results suggest this feral population remains an admixed swarm with continued low levels of European ancestry and a greater presence of African‐derived mitochondrial genetic composition.

In-Hive Miticides and their Effect on Queen Supersedure and Colony Growth in the Honey Bee ( Apis mellifera )

Honey bees (Apis mellifera) contribute an estimated

The combined effects of miticides on the mating health of honey bee (Apis mellifera L.) queens

200 billion annually to the global economy, primarily through crop pollination. Despite their importance, the number of managed honey bee colonies continues to decline. Recent surveys have shown that colony losses are attributed in great part to problems associated with the ectoparasitic mite Varroa destructor, and with issues related to poor queen quality (particularly premature queen replacement), which often result in decreased colony productivity and increased risk of mortality. We aimed to investigate how sublethal exposure to beekeeper-applied miticides affects honey bees at both the individual (queen) and colony levels. We did so by comparing the growth (comb built, brood produced, food stored, and worker population), queen supersedure rates, and winter survival probabilities of colonies that were headed by queens that were raised in either miticide-laden or miticide-free beeswax cups then housed in hives that were either treated with miticides or left untreated. Contrary to our prediction, we found that treated colonies headed by queens raised in miticide-laden beeswax built significantly more worker and drone comb, and stored more food, than any other colony treatment. We did not, however, observe any other significant effect of colony treatment on the amount of brood production, worker population size, queen supersedure rate, or colony winter survival. Thus, we failed to observe a direct negative effect of miticide exposure at the colony level. More studies are needed to further test the potentially detrimental synergistic effects of in-hive miticides on honey bee health at the colony level.

Endopolyploidy Changes with Age-Related Polyethism in the Honey Bee, Apis mellifera

The honey bee, Apis mellifera L., plays a pivotal role in the US economy, contributing an estimated

An oligarchy of nest-site scouts triggers a honeybee swarm’s departure from the hive

17 billion annually, primarily through crop pollination. Despite their importance, the number of managed honey bee colonies available for pollination services has dropped dramatically during the last decade, threatening crop yields across the country. One of the main culprits of such declines is the varroa mite, Varroa destructor, a pest of honey bees that, when present in high numbers inside a hive, causes colonies to collapse and die. For almost 20 years, varroa mites have been controlled primarily with two in-hive miticides: the pyrethroid tau-fluvalinate (Apistan) and the organophosphate coumaphos (Checkmite+). Various studies have revealed that the exposure of honey bee colonies to sublethal levels of these chemicals can lead to colony-wide health problems. In this study, we looked at the combined effects of fluvalinate and coumaphos on the reproductive health of honey bee queens. We did so by raising queens in either miticide-free beeswax or beeswax containing known concentrations of both coumaphos and fluvalinate. Upon their emergence and successful mating, we took several standard measures of queen’s reproductive health. We found that queens reared in miticide-laden beeswax were not significantly smaller in size, but the spermatheca analysis showed significantly lower sperm counts and viability, and higher mating frequency, compared to queens reared in miticide-free beeswax. Our results indicate that exposure to miticides during development severely compromises queen’s reproductive health. Our findings also demonstrate the importance of the potentially detrimental combined effects of common in-hive miticides on colony health.

Assessing the role of β-ocimene in regulating foraging behavior of the honey bee, Apis mellifera

Honey bees (Apis mellifera) exhibit age polyethism, whereby female workers assume increasingly complex colony tasks as they age. While changes in DNA methylation accompany age polyethism, other DNA modifications accompanying age polyethism are less known. Changes in endopolyploidy (DNA amplification in the absence of cell division) with increased larval age are typical in many insect cells and are essential in adults for creating larger cells, more copies of essential loci, or greater storage capacity in secretory cells. However, changes in endopolyploidy with increased adult worker age and polyethism are unstudied. In this study, we examined endopolyploidy in honey bee workers ranging in age from newly emerged up to 55 days old. We found a nonsignificant increase in ploidy levels with age (P < 0.1) in the most highly endopolyploid secretory cells, the Malpighian tubules. All other cell types decreased ploidy levels with age. Endopolyploidy decreased the least amount (nonsignificant) in neural (brain) cells and the stinger (P < 0.1). There was a significant reduction of endopolyploidy with age in leg (P < 0.05) and thoracic (P < 0.001) muscles. Ploidy in thoracic muscle dropped from an average of 0.5 rounds of replication in newly emerged workers to essentially no rounds of replication (0.125) in the oldest workers. Ploidy reduction in flight muscle cells is likely due to the production of G1 (2C) nuclei by amitotic division in the multinucleate striated flight muscles that are essential to foragers, the oldest workers. We suggest that ploidy is constrained by the shape, size and makeup of the multinucleate striated muscle cells. Furthermore, the presence of multiple 2C nuclei might be optimal for cell function, while higher ploidy levels might be a dead-end strategy of some aging adult tissues, likely used to increase cell size and storage capacity in secretory cells.

Survey for Nosema spp. in Belize apiaries

Animals that travel in groups must synchronize the timing of their departures to assure cohesion of the group. While most activities in large colonies of social insects have decentralized control, certain activities (e.g., colony migration) can have centralized control, with only a special subset of well-informed individuals making a decision that affects the entire colony. We recently discovered that a small minority of individuals in a honeybee colony—an oligarchy—decides when to trigger the departure of a swarm from its hive. The departure process begins with some bees producing the worker-piping signal (the primer for departure) and is followed by these bees producing the buzz-run signal (the releaser for departure). In this study, we determined the identity of these signalers. We found that a swarm’s nest-site scouts search for potential nest cavities prior to the departure of the swarm from its hive. Furthermore, we found that the predeparture nest-site scouts are the sole producers of the worker-piping signal and that they are the first producers of the buzz-run signal. The control of the departure of a honeybee swarm from its hive shows how a small minority of well-informed individuals in a large social insect colony can make important decisions about when a colony should take action.