Absence of Nepotism in Waggle Communication of Honeybees (Apis mellifera)

Honeybees are a model organism to study the genetic basis oftaskspecializationinsocialinsects due to the polyandrous queen (Robinson et al., 2005). Generally, from six to twenty subfamilies (paternity) co-exit within a honeybee colony that are genetically different, and these genetic differences have also translated into different behavior preference (Page & Robinson, 1991). Genetic variability has been described for such behavioral traits as nectar and pollen foraging (Page & Robinson, 1991), nest site scouting (Robinson & Page, 1989), plant choice for pollen collection (Oldroyd et al., 1992), foraging distance (Oldroyd et al., 1993), water collecting and scenting (Kryger et al., 2000), fanning (Su et al., 2007), emergency queen-cell building (Xie et al., 2008), mite (Varroa destructor) parasitism rate (Liu et al., 2009), swarming (Huang & Zeng, 2009), survival differences (Wang et al., 2012) and feeding preference (Yi et al., 2018).

Honeybees have evolved numerous mechanisms to increase colony-level foraging efficiency, mainly the combined system of scout-recruit division of labor and recruitment communication (von Frisch, 1967; Seeley, 1998). This recruitment process incorporates information about the food reward, the colony food stores and the environmental food availability (George & Brockmann, 2019). At the individual level, the efficiency of a scout depends on its ability to find and inform the nest mates of the food source. A successful forager performs waggle dances on the surface of the comb where it interacts with nectar receivers and dance followers (Seeley, 1998). The responses to the waggle dance signal reflect the contextual information possessed by various honeybees on the dance floor (Seeley & Towne, 1992). Honeybee workers might be able to behave nepotistically and favor the reproductive success of their subfamily (Getz et al., 1983; Page et al., 1989, 1990).

Oldroyd (1991) showed that a strong tendency for recruits to follow their super-sister dancers. This may increase honeybee colony efficiency in dance communication. Arnold (2002) suggested that sub-familial variance for propensity may vary both for waggle and tremble dances. However, neither in a colony consisting of only two subfamilies nor in a colony consisting of seventeen subfamilies was there any evidence of subfamily discrimination among dancers and their followers foraging from artificial feeding site that provided sucrose solution (Kirchner & Arnold, 2001). However, the result might be biased by the subfamilies’ preferences of nectar and pollen foraging (Page & Robinson, 1991). In order to avoid the foraging preference, we used colonies during natural foraging rather than using an artificial feeder. The aim of the present study is to determine any nepotism in dancing recruitment under natural conditions. We therefore determined the subfamily frequencies of natural mated colonies, as well as the subfamily of the dancers and followers through microsatellite genetic markers.

Genotypes of paternity were calculated in each colony respectively (Tab. 2). As the subfamily frequencies were unequal in our samples, we extended the statistical analysis by considering the subfamilies separately. Colony A consisted of fourteen subfamilies, and twenty-two of 117 dance followers were super-sisters of the dancers and ninety-five were half-sisters (Tab. 2, 3). Colony B consisted of twelve subfamilies, where twenty-three of ninety-three analyzed followers were super-sisters of the dancers and seventy were half-sisters (Tab. 2, 4). In colony A, a single group showed significant nepotism for workers to follow super-sister dancer (chisquare test: χ² = 7.778, df = 1, P = 0.021). However, significant preference to nepotism was not observed between the distribution of the waggle dancers and that of the dance followers overall in colony A (chi-square test: c²= 3.760, df = 6, P = 0.768) (Tab. 3). For colony B, neither individual group nor whole colony showed a significant preference to nepotism between the waggle dancers and that of the dance followers on the whole (chi-square test: c² = 5.516, df = 7, P = 0.498) (Tab. 4).

For our study, the data show that there was no subfamily nepotism among dancers and their followers. Oldroyd (1991) reported that honeybees dance preferentially with their super-sisters, which suggests a strong tendency to recruit super-sisters and indicates subfamily discrimination. The tendency of a recruit to follow a dancer was affected by the subfamily of the recruit, the subfamily of the dancer, foraging preferences of dancer and what she was carrying (Waddington, 1989; Page & Robinson, 1991). Here we show that recognition between super-sisters and half-sisters is at least not a general feature of the dance communication system.

Honeybees are eusocial insects, specialized in information sharing, division and cooperation. Even though the location and quality of the food resource, as well as the season shapes the foraging behavior, any significant impacts on nepotism have not been identified (Oldroyd et al., 1992, 1993, 1994). Kirchner and Arnold (2001) found no evidence for subfamily discrimination among dancers and their followers in a colony. However, honeybees just foraged from an artificial feeding site providing sucrose solution. So, the result might be due to different foraging preferences of the subfamilies. Gilley (2014) also suggest that the waggle-dance hydrocarbons play an important role in honeybee foraging recruitment by stimulating foragers to perform waggle dances. In addition, dance activity for food sources was regulated by an inter-play between individual response thresholds and the social context obtained through interaction with nest mates (George & Brockmann, 2019). Thus, honeybee would unlikely change the tendency to follow dancers due to the degree of relatedness. The single significant nepotism group found in our data might be due to the difficulty of sampling and the low number of followers in that group. This helps the colony to efficiently utilize its foraging force to effectively exploit food sources in its environment. Thus, we conclude that honeybees do not show kin recognition in dance-recruit associations under natural conditions.