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Myriapods (e.g., centipedes and millipedes) display a simple homonomous body plan relative to other arthropods. All members of the class are terrestrial, but they attained terrestriality independently of insects. Myriapoda is the only arthropod class not represented by a sequenced genome. We present an analysis of the genome of the centipede Strigamia maritima. It retains a compact genome that has undergone less gene loss and shuffling than previously sequenced arthropods, and many orthologues of genes conserved from the bilaterian ancestor that have been lost in insects. Our analysis locates many genes in conserved macro-synteny contexts, and many small-scale examples of gene clustering. We describe several examples where S. maritima shows different solutions from insects to similar problems. The insect olfactory receptor gene family is absent from S. maritima, and olfaction in air is likely effected by expansion of other receptor gene families. For some genes S. maritima has evolved paralogues to generate coding sequence diversity, where insects use alternate splicing. This is most striking for the Dscam gene, which in Drosophila generates more than 100,000 alternate splice forms, but in S. maritima is encoded by over 100 paralogues. We see an intriguing linkage between the absence of any known photosensory proteins in a blind organism and the additional absence of canonical circadian clock genes. The phylogenetic position of myriapods allows us to identify where in arthropod phylogeny several particular molecular mechanisms and traits emerged. For example, we conclude that juvenile hormone signalling evolved with the emergence of the exoskeleton in the arthropods and that RR-1 containing cuticle proteins evolved in the lineage leading to Mandibulata. We also identify when various gene expansions and losses occurred. The genome of S. maritima offers us a unique glimpse into the ancestral arthropod genome, while also displaying many adaptations to its specific life history.

To link to full-text access for this article, visit this link: http://dx.doi.org/10.1016/j.anbehav.2009.01.034 Byline: Joany C. Galindo Lopez (a), F. Bernhard Kraus (a)(b) Abstract: Drone congregations are a widespread phenomenon among stingless bee species. Such congregations can consist of more than 1000 individuals and persist for several days or even weeks. Because congregations often form directly outside of conspecific colonies, it has been hypothesized that the presence of a virgin queen inside the colony triggers the aggregation of the drones. Here we used drone congregations of the Neotropical stingless bee Scaptotrigona mexicana to test this hypothesis. We performed behavioural experiments where the drones of a given congregation could decide between a previously chosen colony and an unknown colony as the site of formation for a congregation. Our results show that drone congregations are not associated with a particular colony (or its content) but rather with specific sites at the test location. Thus, the content of a colony (e.g. the presence of a virgin queen) is unlikely to be the trigger for the formation of a congregation. Furthermore, we found that pheromonal markings were used for short-distance orientation of drones towards a given site. Choice experiments of individual drones in the laboratory showed that drones were attracted to groups of other drones, although they did not react to groups of workers. These results imply that once a given site is chosen by some drones, they will attract more drones via positive feedback from the visual presence and odours of increasing numbers of drones. Author Affiliation: (a) El Colegio de la Frontera Sur (ECOSUR), Departamento Entomologia Tropical, Mexico (b) Institut fur Biologie, Martin-Luther-University, Halle-Wittenberg, Germany Article History: Received 25 September 2008; Revised 6 November 2008; Accepted 22 January 2009 Article Note: (miscellaneous) MS. number: A08-00614

Abstract Background Cooperation and conflict in social insects are closely linked to the genetic structure of the colony. Kin selection theory predicts conflict over the production of males between the workers and the queen and between the workers themselves, depending on intra-colonial relatedness but also on other factors like colony efficiency, sex ratios, cost of worker reproduction and worker dominance behaviour. In most bumblebee (Bombus) species the queen wins this conflict and often dominates male production. However, most studies in bumblebees have been conducted with only a few selected, mostly single mated species from temperate climate regions. Here we study the genetic colony composition of the facultative polyandrous neotropical bumblebee Bombus wilmattae, to assess the outcome of the queen-worker conflict over male production and to detect potential worker policing. Results A total of 120 males from five colonies were genotyped with up to nine microsatellite markers to infer their parentage. Four of the five colonies were queen right at point of time of male sampling, while one had an uncertain queen status. The workers clearly dominated production of males with an average of 84.9% +/- 14.3% of males being worker sons. In the two doubly mated colonies 62.5% and 96.7% of the male offspring originated from workers and both patrilines participated in male production. Inferring the mother genotypes from the male offspring, between four to eight workers participated in the production of males. Conclusions In this study we show that the workers clearly win the queen-worker conflict over male production in B. wilmattae, which sets them apart from the temperate bumblebee species studied so far. Workers clearly dominated male production in the singly as well the doubly mated colonies, with up to eight workers producing male offspring in a single colony. Moreover no monopolization of reproduction by single workers occurred.

The article by Harpur et al. (2012) 'Management increases genetic diversity of honey bees via admixture' concludes that '...honey bees do not suffer from reduced genetic diversity caused by management and, consequently, that reduced genetic diversity is probably not contributing to declines of managed Apis mellifera populations'. In the light of current honeybee and beekeeping declines and their consequences for honeybee conservation and the pollination services they provide, we would like to express our concern about the conclusions drawn from the results of Harpur et al. (2012). While many honeybee management practices do not imply admixture, we are convinced that the large-scale genetic homogenization of admixed populations could drive the loss of valuable local adaptations. We also point out that the authors did not account for the extensive gene flow that occurs between managed and wild/feral honeybee populations and raise concerns about the data set used. Finally, we caution against underestimating the importance of genetic diversity for honeybee colonies and highlight the importance of promoting the use of endemic honeybee subspecies in apiculture. [ABSTRACT FROM AUTHOR]

Drone aggregations are a widespread phenomenon in many stingless bee species (Meliponini), but the ultimate and proximate causes for their formation are still not well understood. One adaptive explanation for this phenomenon is the avoidance of inbreeding, which is especially detrimental for stingless bees due to the combined effects of the complementary sex-determining system and the small effective population size caused by eusociality and monandry. We analyzed the temporal genetic dynamics of a drone aggregation of the stingless bee Scaptotrigona mexicana with microsatellite markers over a time window of four weeks. We estimated the drones of the aggregation to originate from a total of 55 colonies using sibship re-construction. There was no detectable temporal genetic differentiation or sub-structuring in the aggregation. Most important, we could exclude all colonies in close proximity of the aggregation as origin of the drones in the aggregation, implicating that they originate from more distant colonies. We conclude that the diverse genetic composition and the distant origin of the drones of the S. mexicana drone congregation provides an effective mechanism to avoid mating among close relatives.

Division of labour is a fundamental property of any social system. The specialization of different individuals in different tasks increases the overall work performance and efficiency. Specialization is thought to be the very foundation of the success of human societies but also in complex colonies of social insects. In human societies an advanced form of division of labour, especially since the industrialisation, is shift work, where individuals perform the same task but in subsequent cohorts in time. Although social insects can measure and are aware of time, shift work has not been documented in colonies of social insects so far. We observed foragers of two honeybee (Apis mellifera) colonies (approximately 140 workers each) and genotyped them with microsatellite DNA markers. We determined paternity and assigned them to the various subfamilies in the colony to test whether there is genetic variance for shift work in foraging honeybees. We could show that the patriline identity of the foragers had a significant effect on foraging either in the morning or evening. Individual foragers differed in their preference for the "early" or "late" shift, and shift work indeed existed in the colony.

Elaborate division of labour has contributed significantly to the ecological success of social insects. Division of labour is achieved either by behavioural task specialization or by morphological specialization of colony members. In physical caste systems, the diet and rearing environment of developing larvae is known to determine the phenotype of adult individuals, but recent studies have shown that genetic components also contribute to the determination of worker caste. One of the most extreme cases of worker caste differentiation occurs in the army ant genus Eciton, where queens mate with many males and colonies are therefore composed of numerous full-sister subfamilies. This high intracolonial genetic diversity, in combination with the extreme caste polymorphism, provides an excellent test system for studying the extent to which caste determination is genetically controlled. Here we show that genetic effects contribute significantly to worker caste fate in Eciton burchellii. We conclude that the combination of polyandry and genetic variation for caste determination may have facilitated the evolution of worker caste diversity in some lineages of social insects.