Zayed / Kent Genomics, Physiology and Behaviour of Social Insects

1. Auflage 2015
ISBN: 978-0-12-802348-8
Verlag: Elsevier Science & Techn.
Format: EPUB
Kopierschutz: 6 - ePub Watermark

E-Book, Englisch, Band Volume 48, 380 Seiten

Reihe: Advances in Insect Physiology

Physiology, Behavior, Genomics of Social Insects provides comprehensive information on the social insect groups described, including new and unique reviews on emerging model social organisms. The book's interdisciplinary approach integrates behavior, genomics, and physiology, providing readers with great insights into the present state of a rapidly expanding area of research. It also discusses areas where new research tools will bring hope to longstanding problems. - Provides the latest research on the genomics, behavior and physiology of social insects - Presents diverse and authoritative syntheses on the relationship between genomics, physiology, and the fascinating behavior of social insects - Takes an in-depth look of the current state of social insect research and its future path

Autoren/Hrsg.

Zayed, Amro

Kent, Clement

Leseproben

Chapter Two The Physiological and Genomic Bases of Bumble Bee Social Behaviour
Etya Amsalem*; Christina M. Grozinger*; Mario Padilla*; Abraham Hefetz†,1    * Department of Entomology, Center for Pollinator Research, Center for Chemical Ecology, Huck Institutes of the Life Sciences, The Pennsylvania State University, University Park, Pennsylvania, USA
† Department of Zoology, George S. Wise Faculty of Life Sciences, Tel Aviv University, Ramat Aviv, Tel Aviv, Israel
1 Corresponding author: email address: [e-mail] Abstract
Bumble bees are an outstanding model system in which to study the organization and evolution of complex social behaviour. Bumble bees pass through several distinct phases during their annual life cycle, including solitary and eusocial phases, and the final stage of the colony cycle is marked by intense competition among the queen and workers over the production of males. Furthermore, there are approximately 250 species of bumble bees, and of the few species that have been examined, it is clear that multiple life history strategies are possible. Thus, the ultimate and proximate mechanisms underlying co-operation, conflict, and behavioural plasticity can readily be examined in bumble bees. Here, we describe the current state of knowledge about the evolutionary, ecological, behavioural, physiological, chemical, and genomic mechanisms and factors underpinning bumble bee social behaviour throughout the colony cycle. We highlight long-standing questions in the field and discuss how advances in genomics and comparative approaches across bumble bee species can provide profound insights into this fascinating system and the evolution of social behaviour. Keywords Bumble bees Social behaviour Sociogenomics Bombus terrestris Pheromones Social conflicts Abbreviations CA corpora allata CP competition phase JH juvenile hormone Kr-h1 Krüppel-homolog 1 QLC queenless compartment Pre-CP pre-competition phase QEC queen-excluded compartment QL queenless QR queenright QRC queenright compartment Vg/vg vitellogenin (protein/mRNA) 1 Introduction
Bumble bees are one of the most conspicuous bees in meadows of the temperate zones. They comprise about 250 species, all of which belong to the genus Bombus, except for the social parasitic species that belong to the genus Psythirus. Most bumble bees live in the temperate zones of the Northern hemisphere, but some species also occupy temperate zones of the Southern hemisphere and some are even present in tropical zones (Cameron et al., 2007; Michener, 1974; Sakagami, 1976; Williams et al., 2008). All species in the genus Bombus are social but are misleadingly considered ‘primitively’ eusocial due to their solitary mode of colony foundation, their annual colony life cycle, and because the queens possess pollen-collecting morphological characters. However, this classification is not completely accurate because in most species, castes are clearly recognizable by size and thus are morphologically distinct, and females also store food in cells different from the brood cells, both characteristics of highly eusocial bees (Goulson, 2010; Michener, 1974; Wilson, 1971). Bumble bees are both economically important pollinators and have served as a principal model system for a variety of studies in social behaviour and ecology (Goulson, 2010). Moreover, with the development of new genomic tools and resources (Sadd et al., 2015), bumble bees are emerging as an outstanding model system to study the sociogenomic mechanisms mediating social behaviours. With few exceptions, bumble bee colonies have an annual life cycle, which encompasses first a solitary phase in which the queen cares for the first-generation brood, then a co-operative eusocial phase with a clear reproductive division of labour, and finally transitions to a period of intense competition and conflict. Thus, bumble bees can be used to study the proximate mechanisms that regulate complex social behaviour, as well as the ultimate mechanisms underlying the evolution of these behaviours. Though there are hundreds of bumble bee species, studies have focused on only a handful of species, particularly Bombus terrestris. In this chapter, we will focus on the physiology and genomic mechanisms underlying social behaviour in B. terrestris and refer to other species whenever information is available. 1.1 The B. terrestris colony life history
The general descriptions of bumble bee life histories, nesting, and social behaviours were published before (Alford, 1978; Duchateau and Velthuis, 1988; Goulson, 2003; Michener, 1974). Here, we briefly outline their life cycle with emphasis on traits that might have an impact on their social behaviour and social physiology (Fig. 1). Since most of the studies pertaining to the physiology and genomics of bumble bees were performed with B. terrestris, we will first describe its life cycle, and thereafter allude to deviations from this general scheme with references to how it may affect social structure. It is also noteworthy that the geographical distribution of B. terrestris is very large, from Northern Europe to the Middle East, and probably encompasses several cryptic species or at least sub-species (Lecocq et al., 2013). This can explain the occasional differences in traits investigated by different laboratories that may have used different populations (e.g. Central Europe and Israel). Figure 1 Bombus terrestris life cycle. Colonies rear one generation per year. New queens emerge near the end of colony cycle and leave the colony shortly after. During the solitary phase, the queens mate and enter a winter diapause that can last 6–9 months. Upon completion of diapause, queens forage, activate their ovaries, and lay their first brood (solitary phase). The colony's social phase begins with the emergence of the first worker (eusocial phase). The queen is the sole reproducer until the onset of the competition phase where females aggressively compete over male production. Males are produced at the ‘switch point’, where the queen switches from diploid egg to haploid egg production. The timing of the switch point varies between colonies and is likely influenced by ecological conditions. Gynes are produced towards the end of life cycle. Graphical design by Nick Sloff, Department of Entomology, Pennsylvania State University. The colony cycle in B. terrestris starts with the diapause of mated queens, which can be initiated in the fall and lasts for 6–9 months (Alford, 1969b). Mated queens search for a subterranean cavity where they overwinter relying on their food reserves for survival (see Section 3.2, for more information). While in nature diapause is required to survive the winter, laboratory-reared queens can be induced to bypass diapause and are still able to produce colonies. These colonies, however, produce a greater number of gynes (future queens) (Beekman and van Stratum, 2000; Gosterit and Gurel, 2009). In nature, queens that skip diapause are bivoltine and are therefore selected to produce reproductives earlier in order for the next-generation queens to survive the approaching winter (see Section 1.3), and thus these laboratory-reared colonies may be reflecting a bivoltine life cycle. After emerging from diapause, the founder queen searches for a nesting site (in B. terrestris nests are underground, usually in abandoned rodent burrows). Here, she builds several wax cells, provisions them with pollen, and lays the first batch of eggs (8–16 eggs). As the first batch of larvae develops, the queen continues foraging to provide them with pollen and nectar. When the larvae pupate, the queen typically builds additional egg cells on top of them to rear the second cohort of workers, which she continuously provides with pollen and nectar. This constitutes the solitary phase of the colony cycle. In the next, eusocial phase of the colony, the queen stops foraging and is engaged solely in egg laying, while the workers take over all nest duties. During this phase, the nest population grows exponentially. After several generations of worker production and towards the end of the foraging season, reproductives (males and female gynes) are produced. Gyne production follows the ‘Bang-Bang’ strategy (Macevicz and Oster, 1976; Oster and Wilson, 1978), e.g., an abrupt shift from producing workers to producing gynes, consistent with B. terrestris having annual colonies and being semelparous (i.e. reproducing only once in a lifetime). Timing of male production in B. terrestris is more complex:...