Domestication of Honey Bees Was Associ- Ated With
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MEC 5641 Dispatch: 9.5.12 Journal: MEC CE: Sankara Rajan I. Journal Name Manuscript No. B Author Received: No. of pages: 3 PE: Punitha Molecular Ecology (2012) 1 2 3 NEWS AND VIEWS 4 5 6 7 PERSPECTIVE developed for other livestock (Foote 2002). There is a sig- 8 nificant industry that breeds and propagates bees for sale 9 Domestication of honey bees was associ- to honey producers and pollinators (Delaney et al. 2009; 10 ated with expansion of genetic diversity Laidlaw & Page 1997). Yet despite these advances and 11 some early attempts at stock certification (Witherell 1976), 12 BENJAMIN P. OLDROYD no specific breeds of bees have emerged that you could 13 Behaviour and Genetics of Social Insects Lab, School of reliably distinguish from other bees. Thus, instead of refer- 14 Biological Sciences, University of Sydney, Sydney, NSW 2006, ring to the breed they keep, beekeepers tend to describe 15 Australia their bees by subspecies, or perhaps the breeder they 16 bought their stock from. If a beekeeper tells you ‘I keep 17 2 Xxxx. Italians’, he or she means a yellow bee, probably from Cali- 18 fornia, that has some ancestry in Apis mellifera ligustica Keywords: Apis mellifera, domestication, genetic diversity, 19 from Italy. 3 SNP 20 In this issue, Harpur et al. (2012) delve deeply into the 21 Received 30 March 2012; revision received 17 April 2012; ancestry of the domestic honey bee and come up with fas- 22 accepted 23 April 2012 cinating and novel findings. Some previous studies of 23 commercial honey bees have suggested that, as with other 24 livestock, bee populations are characterized by low genetic 25 The domestic turkey is a different creature from its wild diversity and that low diversity has arisen as a result of 26 ancestors. It is much larger, and its growth rate is prodi- domestication (Schiff et al. 1994; Schiff & Sheppard 1996; 27 gious (Rose 1996). Famously, some breeds cannot even Delaney et al. 2009; vanEngelsdorp & Meixner 2010; Jaffe´ 28 mate because of the male’s large breast and must be artifi- et al. 2010; Meixner et al. 2010). Low genetic diversity is 4 29 cially inseminated. So, too most dog breeds are unrecogniz- of particular concern for honey bees, because intracolonial genetic diversity is essential to colony health (Seeley & 30 able as the wolves from which we once bred them (Vila` Tarpy 2007) and fitness (Mattila & Seeley 2007; Oldroyd & 31 et al. 1990; Wayne & vonHoldt 2012). This pattern of phe- notypic change in which domesticated plants and animals Fewell 2007; Page 1980). Indeed, some authors have specu- 32 differ strongly from their wild ancestors is common lated that recent declines in honey bee populations in 33 (Andersson & Georges 2004). Domestication is often associ- Europe and North America (vanEngelsdorp et al. 2009b; 34 ated with a reduction in additive genetic variance, fixation vanEngelsdorp & Meixner 2010) and the phenomenon of 35 of alleles associated with traits of economic importance, ‘Colony Collapse Disorder’ (CCD; vanEngelsdorp et al. 36 reduction in brain size, increased tameness, change in body 2009a) may be linked to declining genetic diversity 37 size and conformation, and the development of breed-spe- (Oldroyd 2007; vanEngelsdorp & Meixner 2010). 38 cific characteristics (Diamond 2002; Hall & Bradley 1995). Harpur et al. (2012) argue against this view, showing 39 Many breeds of domestic animals are incapable of living in that unlike other livestock breeding, honey bee breeding 40 the wild, and their recent wild ancestors are extinct. A case seems to have increased rather than decreased genetic 41 in point is the domestic silk worm, Bombyx mori (Yukuhiro diversity in commercial strains. Commercial honey bees 42 et al. 2002). are genetically diverse because, rather than breeding for 43 The honey bee, in contrast, has never been properly breed-specific characteristics within a defined population, 44 domesticated (Oxley & Oldroyd 2010). Instead, we have bee breeding is often characterized by bringing in new 45 learned to manage them—albeit in sophisticated ways—by genetic material from diverse sources. 46 providing them with hives that make it easier to rob them Most commercial honey bees are derived from Europe. 47 of their honey and wax (Crane 1999), or lug them around The honey bees of Europe arose from two independent 48 for pollination jobs. But in most respects, domestic bees migration events from source populations in Africa (Whit- 49 remain largely unchanged from their wild cousins. field et al. 2006). Each migration event occurred during a 50 The lack of domestication of bees is a bit strange. period of relatively mild climate that followed a period of 51 Humans have husbanded bees in hives for at least glaciation (Ruttner 1988). The result of these two coloniza- tions is that there are two major lineages of honey bee in 52 7000 years (Bloch et al. 2010)—far longer than turkeys have Europe: the M and the C (Franck et al. 1998; Garnery et al. 53 been domesticated. Reliable artificial insemination was invented in the 1940s (Laidlaw 1944), shortly after it was 1992; Whitfield et al. 2006). The honey bees of Western 54 Europe (lineage M) are (or at least were) dark and include 55 the subspecies A. m. mellifera (Ruttner 1988). The honey 56 Correspondence: Benjamin P. Oldroyd, Fax: (029) 351 4771; 1 bees of eastern Europe (lineage C) are variable in colour 57 E-mail: [email protected] Ó 2012 Blackwell Publishing Ltd 2 NEWS AND VIEWS: PERSPECTIVE 1 2 and behaviour and adapted to various climatic zones and wing, well away from their colony, with about 20 males 3 are classified in several subspecies including A. m. carnica drawn from a population sourced from every colony in a 3 A. m. ligustica et al. 4 (dark) and (yellow) (Ruttner 1988). to 4 km radius (Baudry 1998). This means that feral Harpur et al. (2012) show that the migrant honey bee colonies and the neighbour’s colonies all contribute to the 5 populations established in Canada are mixtures of most of potential pool of mates. 6 the subspecies of Europe and that, at a population level, Finally, it is interesting to consider whether the process 7 commercial honey bee populations are more diverse than of domestication of the honey bee is really all that differ- 8 the European populations from which they are derived. ent to the domestication of other species. Recent genomic 9 No doubt the same is true for the A. mellifera populations studies have revealed that many of our livestock breeds 10 that have been established in New Zealand and Australia are derived from multiple domestication events and show 11 (Chapman et al. 2008; Oxley & Oldroyd 2009). European remarkable phylogenetic complexity (Bruford et al. 2003; 12 populations are less diverse than African populations; no Andersson & Georges 2004; Vila` et al. 2005). Loss of 5 13 doubt the result of ancient population bottlenecks associ- diversity seems recent and may be a direct consequence 14 ated with the migration events. But the migratory activities of modern reproductive technologies and breeding. 15 of commercial beekeepers are stirring the bee population of Maybe beekeepers just have not gone down that road 16 Europe and starting to homogenize it—to the chagrin of yet. 17 some (De la Ru´ a et al. 2009). 18 Harpur et al. (2012) argue that low genetic diversity can- References 19 not be the cause of recent declines in honey bee popula- 20 tions, or the unusually high levels of colony losses Andersson L, Georges M (2004) Domestic-animal genomics: deci- 21 attributed to CCD. But does genetic diversity at a popula- phering the genetics of complex traits. Nature Reviews Genetics, 5, 22 tion scale equate with genetic diversity at an enterprise 202–212. Baudry E, Solignac M, Garnery L et al. (1998) Relatedness among 23 scale or a colony scale? In theory, the bee population of North America could be like the dog population: diverse honeybees (Apis mellifera) of a drone congregation. Proceedings of 24 265 over all, but characterized by subpopulations (breeds) that the Royal Society of London Series B: Biological Sciences, , 2009– 25 2014. are inbred. Certainly, there is the potential for this. Large 26 Bloch G, Francoy TM, Wachtel I et al. (2010) Industrial apiculture commercial queen producers can (and often do) raise thou- 27 in the Jordan valley during Biblical times with Anatolian honey- sands of queens from a single breeder queen (Fig. 1). The 28 bees. Proceedings of the National Academy of Sciences of the United offspring queens are usually mated within a few kilome- 29 States of America, 107, 11240–11244. tres of where they were raised to a selected population of Chapman NC, Lim J, Oldroyd BP (2008) Population genetics of 30 drones. Typically, therefore, all the queens in a commercial commercial and feral honey bees (Apis mellifera) in Western Aus- 31 apiary are sisters, and all the workers are cousins. How- tralia. Journal of Economic Entomology, 101, 272–277. 32 Crane E (1999) The World History of Beekeeping and Honey Hunting. ever, Harpur et al. (2012) show low FIS and genetic admix- 33 ture for the managed Canadian and French populations Routledge, New York. ´ ´ 34 they studied. It therefore seems to me that reduced genetic De la Rua P, Faffe R, Dall’Olio R, Mun˜oz I, Serrano J (2009) Biodi- versity, conservation and current threats to European honeybees. 35 diversity is unlikely to be contributing to CCD (or if CCD Apidologie, 40, 263–284. 36 exists at all—but that is another story). Delaney DA, Meixner MD, Schiff NM, Sheppard WS (2009) Genetic 37 Striking a blow for colony-level diversity is the honey characterization of commercial honey bee (Hymenoptera: Api- 38 bee’s extraordinary mating system.