Choosing an appropriate index to construct dominance hierarchies in animal societies: a comparison of three indices

Colonies of the primitively eusocial wasp Ropalidia marginata consist of a single egg layer (queen) and a number of non-egg-laying workers. Although the queen is a docile individual, not at the top of the behavioral dominance hierarchy of the colony, she maintains complete reproductive monopoly. If the queen is lost or removed, one and only one of the workers [potential queen (PQ)] becomes hyperaggressive and will become the next queen of the colony. The PQ is almost never challenged because she first becomes hyperaggressive and then gradually loses her aggression, develops her ovaries, and starts laying eggs. Although we are unable to identify the PQ when the queen is present, she appears to be a "cryptic heir designate." Here, we show that there is not just one heir designate but a long reproductive queue and that PQs take over the role of egg-laying, successively, without overt conflict, as the queen or previous PQs are removed. The dominance rank of an individual is not a significant predictor of its position in the succession hierarchy. The age of an individual is a significant predictor, but it is not a perfect predictor because PQs often bypass older individuals to become successors. We suggest that such a predesignated reproductive queue that is implemented without overt conflict is adaptive in the tropics, where conspecific usurpers from outside the colony, which can take advantage of the anarchy prevailing in a queenless colony and invade it, are likely to be present throughout the year.reproductive conflict | reproductive succession | eusociality | cooperative breeding | insect societies R eproductive division of labor is the hallmark of insect societies. This is achieved by the differentiation of colony members into reproductive (queen/king) and nonreproductive (worker) castes (1, 2). In insect societies such as those of ants, honeybees, swarm-founding wasps, and higher termites, which are traditionally referred to as highly eusocial, caste determination is achieved by preimaginal physiological processes that channel individuals into distinct reproductive or worker developmental pathways. Thus, caste of an individual is already determined at the time of eclosion and remains irreversible. If the reproductive dies, the colony has to rear a new one from the egg or early larval stage because the workers cannot change their caste in adulthood. In societies such as those of most social bees and wasps, which are traditionally referred to as primitively eusocial, all adult colony members are nearly totipotent and morphologically similar. The process of caste differentiation into reproductives and nonreproductives takes place largely in the adult stage and is based on social interactions among colony members (3-9). This makes the castes flexible and often reversible, so that workers can become queens upon the loss or death of the original queen. In addition to indirect fitness gained as workers, individuals, thus, also have a finite probability of direct reproduction as future queens. Similarly in wood-dwelli...

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“…The index is described in more details in ref. 62. ii) Freq/h of behavioral dominance shown in the queenright colony.…”

Section: Methodsmentioning

confidence: 99%

Reproductive queue without overt conflict in the primitively eusocial wasp Ropalidia marginata

Bang

Gadagkar

2012

Proc. Natl. Acad. Sci. U.S.A.

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“…We calculated ranks based on outcomes from play or agonistic interactions using the Clutton-Brock index, a method that is particularly tolerant of missing pairwise interactions and weights wins highly [37][38][39]. For each marmot in a colony-year, this index is based on the number of marmots that the focal marmot beat (B) plus the total number of marmots which they beat, excluding the subject (Sb), as well as the number of marmots which it lost rspb.royalsocietypublishing.org Proc R Soc B 280: 20130485 to (L) plus the total number which they lost to, excluding the subject (Sl ).…”

Section: (B) Rank Assignmentsmentioning

confidence: 99%

Early play may predict later dominance relationships in yellow-bellied marmots (Marmota flaviventris)

Blumstein

Chung²,

Smith

2013

Proc. R. Soc. B.

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Play has been defined as apparently functionless behaviour, yet since play is costly, models of adaptive evolution predict that it should have some beneficial function (or functions) that outweigh its costs. We provide strong evidence for a long-standing, but poorly supported hypothesis: that early social play is practice for later dominance relationships. We calculated the relative dominance rank by observing the directional outcome of playful interactions in juvenile and yearling yellow-bellied marmots (Marmota flaviventris) and found that these rank relationships were correlated with later dominance ranks calculated from agonistic interactions, however, the strength of this relationship attenuated over time. While play may have multiple functions, one of them may be to establish later dominance relationships in a minimally costly way.

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“…Past studies have dealt with this problem by 'filling in' null dyads, but doing so also causes biases in linearity measures [27,28]. An alternative measure called hierarchy steepness [29] has been used for a comparative analysis, but this is also sensitive to the presence of null dyads [30]. Recently, we proposed a measure termed 'triangle transitivity', which is based on the proportion of transitive triads among all complete triads (a set of three players in which all pairs have interacted: [27]).…”

Section: Introductionmentioning

confidence: 99%

The network motif architecture of dominance hierarchies

Shizuka

McDonald

2015

J. R. Soc. Interface.

101

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The widespread existence of dominance hierarchies has been a central puzzle in social evolution, yet we lack a framework for synthesizing the vast empirical data on hierarchy structure in animal groups. We applied network motif analysis to compare the structures of dominance networks from data published over the past 80 years. Overall patterns of dominance relations, including some aspects of non-interactions, were strikingly similar across disparate group types. For example, nearly all groups exhibited high frequencies of transitive triads, whereas cycles were very rare. Moreover, pass-along triads were rare, and double-dominant triads were common in most groups. These patterns did not vary in any systematic way across taxa, study settings (captive or wild) or group size. Two factors significantly affected network motif structure: the proportion of dyads that were observed to interact and the interaction rates of the top-ranked individuals. Thus, study design (i.e. how many interactions were observed) and the behaviour of key individuals in the group could explain much of the variations we see in social hierarchies across animals. Our findings confirm the ubiquity of dominance hierarchies across all animal systems, and demonstrate that network analysis provides new avenues for comparative analyses of social hierarchies.

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Choosing an appropriate index to construct dominance hierarchies in animal societies: a comparison of three indices

Cited by 69 publications

References 12 publications

Reproductive queue without overt conflict in the primitively eusocial wasp Ropalidia marginata

Reproductive queue without overt conflict in the primitively eusocial wasp Ropalidia marginata

Early play may predict later dominance relationships in yellow-bellied marmots (Marmota flaviventris)

The network motif architecture of dominance hierarchies

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