Ellouise Leadbeater

Nest Inheritance Is the Missing Source of Direct Fitness in a Primitively Eusocial Insect

Fitness benefits from the inheritance of breeding resources may explain why Polistes wasps cooperate with nonrelatives. Animals that cooperate with nonrelatives represent a challenge to inclusive fitness theory, unless cooperative behavior is shown to provide direct fitness benefits. Inheritance of breeding resources could provide such benefits, but this route to cooperation has been little investigated in the social insects. We show that nest inheritance can explain the presence of unrelated helpers in a classic social insect model, the primitively eusocial wasp Polistes dominulus. We found that subordinate helpers produced more direct offspring than lone breeders, some while still subordinate but most after inheriting the dominant position. Thus, while indirect fitness obtained through helping relatives has been the dominant paradigm for understanding eusociality in insects, direct fitness is vital to explain cooperation in P. dominulus.

The dynamics of social learning in an insect model, the bumblebee ( Bombus terrestris )

Bumblebees (Bombus terrestris) are attracted to those particular inflorescences where other bees are already foraging, a process known as local enhancement. Here, we use a quantitative analysis of learning in a foraging task to illustrate that this attraction can lead bees to learn more quickly which flower species are rewarding if they forage in the company of experienced conspecifics. This effect can also be elicited by model bees, rather than live demonstrators. We also show that local enhancement in bumblebees most likely reflects a general attraction to conspecifics that is not limited to a foraging context. Based on the widespread occurrence of both local enhancement and associative learning in the invertebrates, we suggest that social influences on learning in this group may be more common than the current literature would suggest and that invertebrates may provide a useful model for understanding how learning processes based on social information evolve.

A new mode of information transfer in foraging bumblebees

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Insights from insects about adaptive social information use.

Copying others can greatly improve individual fitness and is fundamental for the organisation of societies. Yet in some situations it is better to ignore social information and either explore the world individually or use personal information obtained through prior experience. Insects provide excellent models to study the strategic use of social information, but insights from recent research have rarely been viewed in the light of social learning strategies. Here we discuss how insects tailor their reliance on social information to those circumstances for which it is most beneficial, and suggest that insects and vertebrates use similar information-use strategies. We highlight future research avenues, including the use of molecular tools to study the genetic and genomic basis of social information use.

Bumble-bees learn the value of social cues through experience

Natural selection should lead animals to use social cues (SC) when they are useful, and disregard them when they are not. Theoretical investigation predicts that individuals should thus employ social learning ‘strategies’, but how might such context specificity be achieved on a proximate level? Operant conditioning, whereby the use of SC is reinforced through rewarding results, provides a potential mechanism. We investigate the role of reinforcement in joining behaviour in bumble-bees, Bombus terrestris. When bees visit unfamiliar flower species, they prefer to probe inflorescences where others are also foraging, and here we show that such behaviour is promoted through experience when conspecific presence reliably predicts reward. Our findings highlight a straightforward, but rarely discussed, mechanism by which animals can be selective about when to use SC.

Social transmission of nectar-robbing behaviour in bumble-bees

Social transmission of acquired foraging techniques is rarely considered outside of a vertebrate context. Here, however, we show that nectar robbing by bumble-bees (Bombus terrestris)—an invertebrate behaviour of considerable ecological significance—has the potential to spread through a population at the accelerated rates typical of social transmission. Nectar robbing occurs when individuals either bite through the base of a flower to ‘steal’ nectar (primary robbing) or use robbing holes that others have made (secondary robbing). We found that experience of foraging from robbed flowers significantly promoted the development of primary robbing in previously legitimate foragers, thus implying that the acquisition of nectar robbing by one individual will facilitate its adoption in others. Our findings suggest that the positive feedback effects of social transmission may potentially play an ecologically important role in the relationship between plants and pollinators.

Social Learning: Ants and the Meaning of Teaching

Recent research on ants shows that running in tandem might serve the function of teaching naïve ants about the path to a target. Although these new experiments represent perhaps the most highly controlled study of teaching in animals to date, the findings prompt the question of how teaching formally differs from other forms of communication.

Unrelated Helpers in a Primitively Eusocial Wasp: Is Helping Tailored Towards Direct Fitness?

The paper wasp Polistes dominulus is unique among the social insects in that nearly one-third of co-foundresses are completely unrelated to the dominant individual whose offspring they help to rear and yet reproductive skew is high. These unrelated subordinates stand to gain direct fitness through nest inheritance, raising the question of whether their behaviour is adaptively tailored towards maximizing inheritance prospects. Unusually, in this species, a wealth of theory and empirical data allows us to predict how unrelated subordinates should behave. Based on these predictions, here we compare helping in subordinates that are unrelated or related to the dominant wasp across an extensive range of field-based behavioural contexts. We find no differences in foraging effort, defense behaviour, aggression or inheritance rank between unrelated helpers and their related counterparts. Our study provides no evidence, across a number of behavioural scenarios, that the behaviour of unrelated subordinates is adaptively modified to promote direct fitness interests.

Do inexperienced bumblebee foragers use scent marks as social information

Bumblebees (Bombus spp.) foraging in the field typically reject flowers where they detect the olfactory footprints of previous visitors and hence avoid recently emptied inflorescences. A growing number of studies have begun to illustrate that associative learning shapes the development of this process, in both bumblebees and other bee species. This raises the question of what the default response to such marks is, but little is known about how inexperienced foragers use social information. Here, we offered flower-naive bees a choice between scent-marked flowers and unmarked alternatives and found that individuals neither avoided nor preferred marked flowers. Our findings provide no support for ‘hard-wired’ responses to scent marks in bumblebees and highlight the importance of associative learning in shaping social information use to match local circumstances.

Social Learning: What Do Drosophila Have to Offer?

The recent finding that female Drosophila copy the mate-choice criteria of other females introduces a mainstream model species to the study of how animals use social information.