Benjamin P. Oldroyd

Ancestral Monogamy Shows Kin Selection Is Key to the Evolution of Eusociality

Close relatedness has long been considered crucial to the evolution of eusociality. However, it has recently been suggested that close relatedness may be a consequence, rather than a cause, of eusociality. We tested this idea with a comparative analysis of female mating frequencies in 267 species of eusocial bees, wasps, and ants. We found that mating with a single male, which maximizes relatedness, is ancestral for all eight independent eusocial lineages that we investigated. Mating with multiple males is always derived. Furthermore, we found that high polyandry (>2 effective mates) occurs only in lineages whose workers have lost reproductive totipotency. These results provide the first evidence that monogamy was critical in the evolution of eusociality, strongly supporting the prediction of inclusive fitness theory.

What's killing American honey bees?

American beekeepers reported unusually high rates of colony loss in early 2007 as bees broke from their overwintering clusters. Researchers are struggling to explain whats behind this mysterious disappearance, called colony collapse disorder.

Genetic diversity of the honeybee in Africa: microsatellite and mitochondrial data.

A total of 738 colonies from 64 localities along the African continent have been analysed using the DraI RFLP of the COI–COII mitochondrial region. Mitochondrial DNA of African honeybees appears to be composed of three highly divergent lineages. The African lineage previously reported (named A) is present in almost all the localities except those from north-eastern Africa. In this area, two newly described lineages (called O and Y), putatively originating from the Near East, are observed in high proportion. This suggests an important differentiation of Ethiopian and Egyptian honeybees from those of other African areas. The A lineage is also present in high proportion in populations from the Iberian Peninsula and Sicily. Furthermore, eight populations from Morocco, Guinea, Malawi and South Africa have been assayed with six microsatellite loci and compared to a set of eight additional populations from Europe and the Middle East. The African populations display higher genetic variability than European populations at all microsatellite loci studied thus far. This suggests that African populations have larger effective sizes than European ones. According to their microsatellite allele frequencies, the eight African populations cluster together, but are divided in two subgroups. These are the populations from Morocco and those from the other African countries. The populations from southern Europe show very low levels of ‘Africanization’ at nuclear microsatellite loci. Because nuclear and mitochondrial DNA often display discordant patterns of differentiation in the honeybee, the use of both kinds of markers is preferable when assessing the phylogeography of Apis mellifera and to determine the taxonomic status of the subspecies.

Nature versus nurture in social insect caste differentiation

Recent evidence for genetic effects on royal and worker caste differentiation from diverse social insect taxa has put an end to the view that these phenotypes stem solely from a developmental switch controlled by environmental factors. Instead, the relative influences of genotypic and environmental effects on caste vary among species, ranging from largely environmentally controlled phenotypes to almost purely genetic systems. Disentangling the selective forces that generate variation for caste predisposition will require characterizing the genetic mechanisms underlying this variation, and identifying particular life-history strategies and kin structures associated with strong genetic effects on caste.

Coevolution while you wait: Varroa jacobsoni, a new parasite of western honeybees

The mite Varroa jacobsoni is a brood parasite of the Asian hive bee, Apis cerana. The recent switch in host from A. cerana to the western honeybee, Apis mellifera, offers an exceptional opportunity for studying preadaptation and host-parasite relations. The fact that this host shift appears to have happened on at least two separate occasions, with differing outcomes, must be unique. At another level, the rapacious spread of this mite throughout the world is testimony to the ineffectiveness of international quarantine laws.

Nest Thermoregulation in Social Insects

Abstract Most social insect species are able to regulate the temperature within their nests. In this review, we examine the variety of mechanisms that social insect species have evolved to regulate temperature. We divide these mechanisms into two broad categories: active and passive. ‘Passive’ temperature regulation includes such mechanisms as nest site selection to optimize internal nest temperature, nest structures that permit passive heating or cooling, or simple behaviour such as brood translocation to regions within a nest where temperatures are most favourable. ‘Active’ temperature regulation refers to behaviour where individuals modify nest temperature by physical activity like wing fanning or evaporative cooling. Although there is enormous variation in the thermoregulatory mechanisms, there are also many similarities. All thermoregulatory mechanisms are self-organized and arise from simple rules followed by each individual worker.

The effects of rearing temperature on developmental stability and learning and memory in the honey bee, Apis mellifera

Honey bee workers maintain the brood nest of their colony within a narrow temperature range of 34.5±1.5°C, implying that there are significant fitness costs if brood is reared outside the normal range. However, the effects of abnormal incubation temperatures are subtle and not well documented. Here we show that short-term learning and memory abilities of adult workers are affected by the temperature they experienced during pupal development. In contrast, long-term learning and memory is not significantly affected by rearing temperature. Furthermore, we could detect no effects of incubation temperature on fluctuating asymmetry, as a measure of developmental stability, in workers, queens or drones. We conclude that the most important consequence of abnormal rearing temperatures are subtle neural deficiencies affecting short-term memory rather than physical abnormalities.

Seven suggestive quantitative trait loci influence hygienic behavior of honey bees

Abstract. In 1964, Walter Rothenbuhler proposed a two-gene model to explain phenotypic variance in the remarkable behavior in which honey bee workers remove dead brood from their colonies. Rothenbuhlers model proposed that one locus controls the uncapping of brood cells containing dead pupae, while a second controls the removal of the cell contents. We show here, through molecular techniques and quantitative trait loci (QTL) linkage mapping, that the genetic basis of hygienic behavior is more complex, and that many genes are likely to contribute to the behavior. In our cross, we detected seven suggestive QTLs associated with hygienic behavior. Each detected QTL controlled only 9–15% of the observed phenotypic variance in the character.

Mitochondrial DNA variation in Moroccan and Spanish honey bee populations

The mitochondrial DNAs of 192 Moroccan and 173 Spanish honey bee colonies were characterized by a rapid test involving the restriction by DraI of a PCR‐fragment of the COI‐COII region. In Morocco, we found eight haplotypes, all characteristic of the African (A) lineage, suggesting that most if not all the maternal lineages of the colonies repeatedly imported from Europe over the last 150 years have not contributed mitochondrial genomes to the local population. Using two new genetic distances analogous to the shared allele distance defined for nuclear genes, we showed that Morocco was most probably colonized by two sublineages, one from the north‐east and the other one from the south of the country and that the contact zone between them extends along both sides of the Atlas range. In Spain, we found eight haplotypes characteristic of lineage A (six in common with Morocco) and four of lineage M (the West European lineage). The distribution of haplotypes of both lineages forms a gradient with c. 10% of lineage M in the south of Spain (Seville) and up to 100% in the north (San Sebastian). Three hypotheses are presented to explain the large differences of haplotype frequencies between Moroccan and lineage A Spanish colonies: a non‐Moroccan origin of lineage A in Spain, an ancient Moroccan origin or a recent Moroccan origin with a rapid shift of haplotype frequencies due to a founder effect.

THE AFRICANIZATION OF HONEYBEES (APIS MELLIFERA L.) OF THE YUCATAN:A STUDY OF A MASSIVE HYBRIDIZATION EVENT ACROSS TIME

Abstract Until recently, African and European subspecies of the honeybee (Apis mellifera L.) had been geographically separated for around 10,000 years. However, human‐assisted introductions have caused the mixing of large populations of African and European subspecies in South and Central America, permitting an unprecedented opportunity to study a large‐scale hybridization event using molecular analyses. We obtained reference populations from Europe, Africa, and South America and used these to provide baseline information for a microsatellite and mitochondrial analysis of the process of Africanization of the bees of the Yucatan Peninsula, Mexico. The genetic structure of the Yucatecan population has changed dramatically over time. The pre‐Africanized Yucatecan population (1985) comprised bees that were most similar to samples from southeastern Europe and northern and western Europe. Three years after the arrival of Africanized bees (1989), substantial paternal gene flow had occurred from feral Africanized drones into the resident European population, but maternal gene flow from the invading Africanized population into the local population was negligible. However by 1998, there was a radical shift with both African nuclear alleles (65%) and African‐derived mitochondria (61%) dominating the genomes of domestic colonies. We suggest that although European mitochondria may eventually be driven to extinction in the feral population, stable introgression of European nuclear alleles has occurred.