Recruitment Communication in Stingless Bees (Hymenoptera, Apidae, Meliponini)

Apidologie 35 (2004) 159–182 © INRA/DIB-AGIB/ EDP Sciences, 2004 159 DOI: 10.1051/apido:2004007 Review article Recruitment communication in stingless bees (Hymenoptera, Apidae, Meliponini) James C. NIEH* University of California San Diego, Division of Biological Sciences, Section of Ecology, Behavior, and Evolution, 9500 Gilman Drive, Mail Code 0116, La Jolla, CA 92093-0116, USA (Received 25 August 2003; revised 28 October 2003; accepted 2 December 2003) Abstract – The stingless bees (Hymenoptera, Apidae, Meliponini) have evolved sophisticated communication systems that allow foragers to recruit nestmates to good resources. Over the past 50 years, a growing body of research has shown that foragers can communicate three-dimensional resource location, uncovered several potential communication mechanisms, and demonstrated new information transfer mechanisms. Some of these mechanisms are unique to stingless bees and some may provide insight into how the ability to encode location information, a form of functionally referential communication, has evolved in the highly social bees. The goal of this review is to examine meliponine recruitment communication, focusing on evidence for contact-based, visual, olfactory, and acoustic communication and what these mechanisms can tell us about the evolution of recruitment communication in stingless bees. Meliponini / information transfer / referential communication / recruitment / multimodality 1. INTRODUCTION recruitment communication of the Meliponini and the Apini (Kerr, 1969). Insect societies have evolved information Stingless bees are a monophyletic group transfer systems of remarkable complexity principally found in tropical and subtropical (Wilson, 1971). Highly social bees (honeybees areas of America, Africa, Australia, and parts and stingless bees) use sophisticated methods of Asia (Roubik, 1989). Unlike honeybees, to exploit resources such as pollen, nectar, which consist of approximately 11 species in water, resin, and nest sites (Kerr, 1969). Social one genus, stingless bees consist of several bees can recruit, increase the number of nestmates searching for a particular resource, to hundred species distributed through more than specific or non-specific locations. Mecha- 36 genera (Michener, 2000). Honeybees and nisms that allow highly social bees to commu- stingless bees are the only highly social bees, nicate resource location have been the subject but stingless bees lead more diverse lifestyles, of intensive study, particularly in honeybees, including obligate necrophagy (Roubik, 1982a; which can communicate the polar coordinates Camargo and Roubik, 1991), and can recruit (distance and direction) of a resource through for resources such as dead animals, pollen, nec- a waggle dance (von Frisch, 1967; Dyer, tar, mud, resin, water, and nests (Roubik, 1989). 2002). Researchers have sought to understand Stingless bees also use a greater diversity of how such complex recruitment communica- recruitment communication systems (ranging tion systems have evolved, and some studies from odor trails to the potential referential have therefore focused on stingless bees, encoding of food location) than honeybees, in exploring possible homologies between the which all studied species use the waggle dance * Corresponding author: [email protected] 160 J.C. Nieh (Kerr, 1969; Roubik, 1989; Dyer, 2002). simple, as von Frisch (1967) noted, because Research on stingless bees (Lindauer and Kerr, although they are conceptually straightfor- 1958; Kerr and Esch, 1965; Esch, 1967; Nieh ward, there are several key details that should et al., 2003c) has uncovered intriguing similar- not be overlooked. ities and important differences between recruitment communication in the Meliponini and the 2.1. Intranidal observations Apini (honeybees). However, stingless bees have not been as intensively studied as honey- Lindauer and Kerr (1958) and Esch (1967) bees, and thus our understanding of their biol- pioneered the description of motions and ogy is at an early stage relative to what is known sounds produced inside the nest by foragers of the Apini. returning from a food source. In addition, they Within the last decade, interest in stingless performed intriguing preliminary experiments bee recruitment communication has renewed. testing the function of recruitment sounds. The The goal of this review is to provide an over- general method is to train bees to a feeder at a view of the field while focusing on these new specific location and record the behavior of findings, and examining their implications for these foragers when they return inside the nest understanding the evolution of recruitment (Esch, 1967). It is also possible to mark indi- communication in the Apidae. It has been vidually the entire colony and thus examine argued that olfaction is the sole source of ori- the role of intranidal contacts and the eventual entation information for honeybee recruits success of nestmates in reaching the adver- (Wenner, 2002), and this controversy may also tised food source (Seeley, 1995; Hrncir et al., play out in the stingless bees (Dyer, 2002). 2000). Thus one objective of this review is to examine the evidence for olfactory and non-olfac- 2.2. Feeder arrays tory communication. I will begin by discuss- ing experimental methods and review the Karl von Frisch (1967) developed the gen- literature on recruitment to a specific spatial eral methods for investigating bee location location. I will then examine several potential communication. These methods involve train- communication mechanisms, ranking them in ing bees to an artificial feeder filled with their classically hypothesized order of evolu- sucrose solution (the experimental feeder) at a tionary complexity: contact and visually- particular location. Once trained, these bees based communication, followed by olfactory are known as experienced foragers (Biesmeijer communication, and finishing with a discus- and de Vries, 2001). The investigator then sion of acoustic communication (von Frisch, individually marks a fixed number of trained 1967; Kerr, 1969; Wille, 1983). Although the foragers that are regularly censused to insure phylogeny of the Meliponini remains largely that a constant number of bees visit the feeder. unresolved, the classic ordering gives us a All newcomers (unmarked bees) are then starting point to pursue evolutionary ques- counted and captured or immediately marked. tions. These newcomers are presumptive recruits In the literature, multiple synonyms often that must be shown (1) to come from the col- exist for each species name and there can be ony under study (generally by verifying their disagreement on the appropriate synonym return to the colony) and (2) to have had a high (Roubik, 1989; Michener, 1990; Inoue et al., probability of arriving based upon information 1999; Michener, 2000). I have therefore provided in the nest by the experienced forag- followed the assignments of Michener (2000) ers. Both points can be demonstrated if new- and refer the reader to the original source comers from the colony under study arrive literature for more detailed information to only when trained foragers feed and do not determine the appropriate nomenclature. arrive when these trained foragers are captured. If these criteria are fulfilled, then new- comer recruitment has occurred. 2. METHODOLOGY In order to test whether bees can recruit to a First, it is useful to review the methods gen- specific location, at least two identical feeders, erally used. These methods can be deceptively one control and one experimental, are placed Recruitment communication in stingless bees 161 in an array in which only one spatial dimen- array distances are often the result of working sion is altered at a time. Foragers are trained to in environments where, even in times of the experimental feeder, but not to the control dearth, there are sufficient natural food sources feeder. For example, to test directional com- such that foragers cannot be trained to greater munication, the experimental and control distances and still recruit. It is also possible feeders are placed at different directions equi- that foragers do not usually recruit for natural distant from the nest and at the same height food sources beyond a certain distance. This above the ground. If foragers can communi- remains to be determined. cate the tested dimension, then significantly With stingless bees, small colony sizes also more recruits should arrive at the experimental limit the sample size per experiment and the feeder than at the control feeder. In order to number of experiments that can be conducted. control for potential site bias, it is important to A typical M. quadrifasciata colony contains conduct trials with the training feeder at differ- 300–400 total bees, of which only a fraction are ent locations. foragers (Lindauer and Kerr, 1960). Location These methods are elegant, yet not neces- experiments with such small colonies rapidly sarily simple to execute. Highly social bees use up newcomers, turning them into experi- will only recruit under the right conditions of enced foragers. This occurs because a new- colony need and generally only to an artificial comer is defined as a forager that has never pre- feeder if it provides a resource that is more dif- viously visited any feeder (von Frisch, 1967). ficult to obtain in the natural environment (von Such a rigorous definition is necessary because Frisch, 1967; Roubik, 1989; Seeley, 1995). bees are highly flower constant (Seeley, 1995; Thus

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