The evolution of aggression: can selection generate variability?
06 Jul 1988-Philosophical Transactions of the Royal Society B (Philos Trans R Soc Lond B Biol Sci)-Vol. 319, Iss: 1196, pp 557-570
TL;DR: It is concluded that contests will be settled by non-costly traits only if the value of the contested resource is small relative to the cost of fighting, and that 'honest' signalling of aggressiveness is stable only if individuals giving signals that are inconsistent with their behaviour suffer costs.
Abstract: Three models--the war of attrition, the size game and the badges of dominance game--are described, in which natural selection can maintain genetic variability for aggression. The models differ in whether or not the traits that settle contests are costly in contexts other than fighting, and also in whether signals are used. It is concluded that contests will be settled by non-costly traits only if the value of the contested resource is small relative to the cost of fighting, and that 'honest' signalling of aggressiveness is stable only if individuals giving signals that are inconsistent with their behaviour suffer costs. The literature on 'badges of dominance' in birds is reviewed. New data on great tits, greenfinches and corn buntings show that there is plumage variability within age and sex that sometimes serves to settle contests, and that, in the first two species but not the third, the badges are uncorrelated with size, and settle contests only over trivial resources.
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TL;DR: In this paper, it is argued that an important but neglected evolutionary force on signal design is the psychology of the signal receiver, and that three aspects of receiver psychology (what a receiver finds easy to detect, easy to discriminate and easy to remember) constitute powerful selective forces in signal design.
889 citations
Cites background from "The evolution of aggression: can se..."
...In the following sections we first establish the relevance of learning and memory in both inter- and intraspecific communication, and then explore ways in which memorability considerations can mould signal design....
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...Even in intraspecific assessment signalling (Clutton-Brock & Albon 1979; Maynard Smith & Harper 1988) an individual may benefit from having a signal at least partially because of what receivers take it to mean from their past experience with other signallers....
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...…do not appear to be necessarily correlated with fighting ability; rather they are conventional signals open to low levels of cheating (Maynard Smith & Harper 1988), with some degree of honesty maintained by the fact that cheats with higher status badges than their true quality warrants…...
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...Maynard Smith, J. & Harper, D. 1988....
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...The plumage 'badges of status' found in many bird species (Roper 1986; Whitfield 1987; Maynard Smith & Harper 1988) may be interpreted in this light....
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TL;DR: Secondary sexual characters in many species function both in male-male competition and as cues for female choice, and a literature compilation of existing knowledge of traits with this dual role is compiled.
Abstract: Secondary sexual characters in many species function both in male-male competition and as cues for female choice. Based on a literature compilation of existing knowledge of traits with this dual fu ...
734 citations
TL;DR: While some mating preferences did not originally evolve for adaptive reasons, others may or may not have done so, and a review of the published data reveals some support for the ideas of adaptive choice and honest advertisement.
Abstract: SUMMARY
(i) To find out whether a mating preference could have initially evolved for adaptive reasons, one must determine whether the preferred trait could have provided useful information about mate quality at the time when the preference first arose.
(ii) One way to do so is to determine whether the preference evolved before or after the preferred trait. If the preference evolved first, then it cannot initially have served an adaptive function in mate choice, rather it must have arisen by random drift, or as a pleiotropic consequence of selection acting on other aspects of individual perceptual abilities.
(iii) A number of studies have shown that females exhibit a mating preference (e.g. for movement) in non-sexual contexts also, which suggests that it may have evolved for reasons unconnected to mate choice. In addition, phylogenetic analyses have revealed that in several cases, females of a certain taxon exhibit a preference for a male trait that is absent in a sister taxon and in outgroup taxa, and that this preference is shared by females of the sister taxon tacking the male trait. The principle of parsimony suggests that such a preference has been inherited from a common ancestor, while the preferred trait arose only once in the lineage exhibiting the trait, i.e. that the preference predates the attractive trait.
(iii) While the above evidence indicates that females may possess ‘hidden’ preferences for male traits that are not exhibited by members of their own species, and that in at least some cases males have later evolved display traits that exploit preexisting preferences of this kind, there have been too few historical studies of preference evolution to allow one to assess the frequency of such exploitation. Moreover historical studies cannot provide strong support for the adaptive origin hypothesis, because coevolution of trait and preference (as opposed to exploitation of a pre-existing bias) is compatible with Fisherian models of preference evolution as well as with honest advertisement and the handicap principle. One can conclude only that while some mating preferences did not originally evolve for adaptive reasons, others may or may not have done so.
(iv) To find out whether a mating preference is currently maintained by natural selection because the preferred trait provides useful information about mate quality, one must investigate the phenotypic and genotypic correlates of display, and the fitness consequences of mate choice.
(v) A review of the published data reveals some support for the ideas of adaptive choice and honest advertisement. In a number of species, preferred display traits are correlated with putative measures of quality, and in a small proportion of these, there is evidence that reproductive success and/or offspring performance are higher for individuals mated to attractive partners. Very few studies report a failure to find any such correlates of display or any such benefits.
(vi) While the above result suggests that honest advertisement does sometimes occur in extant populations (which does not necessarily imply that preferred traits originally evolved as reliable indicators of mate quality), the possibility of publication bias means that one cannot assess how widespread it is. More data is needed to remedy this problem, particularly regarding the fitness consequences of mate choice for females. Experimental rather than observational methods are the best means to gather such data. Studies that look for correlates of display, for instance, should rely on experimentally induced rather than natural variation in ‘quality’.
(vii) The most common correlates of male display are age and dominance. The latter observation suggests that there may often be interactions between the processes of intersexual and intrasexual selection.
(viii) There is considerably more evidence to support the idea of female choice for direct than for indirect benefits. At the same time, however, it is apparent that mating decisions are commonly influenced by more than one measure of quality, so that these two kinds of choice need not be independent. To assess this possibility will require more studies of the relationship between male attractiveness and offspring performance.
(ix) Mate choice is frequently based on more than one display trait, and each trait is frequently influenced by more than one aspect of quality. ‘One quality, one trait’ views of honest advertisement are simplistic, and must be abandoned.
(x) Honesty in sexual displays is sometimes maintained by cost (as in strategic handicap models) and sometimes, with approximately equal frequency, by physical necessity (as in revealing handicap models). In some cases, both mechanisms are involved in a single signalling system. To further distinguish between these possibilities will require experimental investigation of display cost, based on manipulation of display traits.
615 citations
TL;DR: Accumulating support is shown for the hypothesis that high quality females show the strongest mate preference, and some of the wider implications of condition-dependent mating decisions and their effect on the strength of sexual selection are examined.
438 citations
Cites background from "The evolution of aggression: can se..."
...Female plumage colouration likely acts as a badge of status [65], as bright females initiate and win a higher proportion of fights compared to dull females [63]....
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TL;DR: It seems that the generally accepted notion that sexual traits are costly is in fact based almost exclusively on indirect evidence and that direct empirical evidence is very scarce.
Abstract: Costs of sexual traits are of central importance to the theory of sexual selection. To qualify as a cost in line with theoretical models, empirical studies must demonstrate that sexual traits cause negative effects on one component of fitness of the trait bearer. Moreover, it must be demonstrated that the costs are differential such that negative effects on fitness are more severe for individuals in poor condition than for individuals in good condition. However, in the current literature, there is confusion over what qualifies as a cost, and costs are often anticipated based on findings of increased expenditure. Consequently, it seems that the generally accepted notion that sexual traits are costly is in fact based almost exclusively on indirect evidence and that direct empirical evidence is very scarce.
429 citations
References
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TL;DR: The drive system includes a motor or engine whose output shaft is connected to the input shaft of a transmission, e.g. speed reducing gear, via an elastic coupling and a clutch, in that order.
Abstract: Animal species vary enormously in the degree to which individuals are similar or different from one another in appearance. In some birds, such as juncos and Harris sparrows, most individuals look different from each other, while in others, such as chickadees and song sparrows, there is little individual variation. These differences in appearance among species require several levels of interpretation. First, an understanding of their social significance is required for us to know what is being communicated by these differences. Second, we should understand the proximate mechanisms by which a correspondence between signal and message is achieved. Finally, we must understand the ecological factors which are ultimately responsible for the social systems and their associated plumage patterns. This paper is addressed only at the social significance of winter plumage variability versus monomorphism. Ordering principles pertaining to animal coloration-theories relating appearance to camouflage, advertisement, physiology, or the formation of search images-are of little help in explaining why some winter birds are highly variable and others monomorphic. The first three of these theories invoke selective principles which are expected to produce monomorphic patterns within populations and, thus, do not relate to plumage variability. Camouflage coloration is expected to select for monomorphism achieved through mimicry of environmental background, substrate color or specific objects. Likewise, advertisement or poster coloration (Lorenz, 1967), evolved by selection for warning coloration, mimicry, species or sex recognition, or advertisement of territorial possession, is not expected to lead to intra-population variability. In some cases of mimicry this is not true, but these cases always select for discontinuous variation, with morphs mimicking various discrete models. Finally, selection upon color pattern for physiological efficiency depends upon assuming one of the radiation colors, generally either black or white (Hamilton, 1973). Small temperate land birds are rarely uniformly white or black, suggesting that physiological needs have probably not been primal in determining their color patterns. Formation of search images does anticipate variability in populations and is sometimes raised to explain the highly variable plumages of certain birds. Clarke (see 1969, and references cited therein) originated the idea to explain the Cepaea snail polymorphisms through apostatic predation, and Croze (1970) has done much
455 citations
TL;DR: From the theoretical treatment of status recognition badges I derive a number of predictions that pertain both to interand intraspecific differences in conspicuous coloration and to the evolution of local song dialects in birds.
Abstract: SYNOPSIS. When a population may be characterized by interference competition for resources, variation in fighting ability among individuals, and repeated confrontations between individuals, together with difficulty of individual recognition, badges of status should invade as recognition marks that render good fighters memorable. Reliability of such badges can be maintained by negative frequency-dependent selection when individuals of different appearance (and status) either play mutually beneficial roles or employ alternate competitive tactics. In territorial social systems intraspecific mimicry of recognition badges should evolve because, in contrast to group-living situations, the cost to a cheat of being discovered is low when individuals are dispersed. The general result of such mimicry is that good and poor fighters become similar in appearance. From the theoretical treatment of status recognition badges I derive a number of predictions that pertain both to interand intraspecific differences in conspicuous coloration and to the evolution of local song dialects in birds.
332 citations
TL;DR: The relation of patterns of variation in badge size to dominance was studied in male house sparrows, Passer domesticus, and males with large badges were more dominant in winter flocks, irrespective of age, body size and body condition index.
290 citations
TL;DR: A new hypothesis to explain the evolutionary stability of subordinance in this system is proposed: dominants and subordinates are adapted, respectively, to defensible and indefensible resource bases, and equal fitness for them is achieved through frequency-dependent selection.
284 citations
TL;DR: The agonistic behavior of the funnel-web building spider, Agelenopsis aperta (Gertsch), was studied using induced encounters between adult females at natural web sites to provide insight into possible sources of variability and their underlying causes.
Abstract: 1.
The agonistic behavior of the funnel-web building spider, Agelenopsis aperta (Gertsch), was studied using induced encounters between adult females at natural web sites. All behavior exhibited by either individual during the course of an encounter was recorded. The results were analyzed through the use of transition matrices and the following multivariate treatments: factor analysis, ordination, and multiple regression. These latter methods were used to provide insight into possible sources of variability and their underlying causes.
2.
Sequence outcome is primarily determined by the relative weight of the two contestants engaged in a territorial dispute. If the size difference is large, the larger of the two individuals wins in a significant number of cases. Home bias is evidenced in cases where body weights are close.
3.
A stereotypy measure is devised that reflects the percent similarity of each sequence of events to an expected sequence (average). The frequency distribution, presence-absence or duration of all behavior patterns observed during the course of the disputes are utilized in measuring stereotypy. The territorial disputes of A. aperta exhibit low stereotypy, averaging 43% on a scale from 0 to 100%.
4.
Low stereotypy is, in part, related to the utilization of 33 different action patterns by spiders in these disputes. Factor analysis is used to express these action patterns in terms of five functional groups including locating behavior, signaling behavior, threat behavior, contact behavior, and a multiple function category. The order of these categories represents increasing cost based on relative estimates of the energy expenditure necessary to complete a specific behavior pattern and the potential for injury through the use of it.
5.
A Bray and Curtis ordination shows the important sources of between sequence variability to be the total energetic cost of the dispute and the complexity of behavior exhibited in it. The factors, in turn, depend on the resident-visitor status of the losing spider and on the relative size of the two contestants. The energetic cost of a dispute is markedly higher in those disputes in which the resident loses her territory. The number of action patterns and total frequency of acts observed are also greater in encounters in which the resident is the losing spider. Behavioral complexity is higher as well in cases where the weights of the two contestants are close.
6.
The variation in the pathways through which the sequences progress is shown to reflect the operation of assessment strategies by A. aperta. Initial assessment of the relative weights of the opponent is made through movements on the web at a distance (locating behavior). Subsequent activities depend on the results of this assessment, the predominant strategy being ‘retaliator’ (Maynard Smith and Price, 1973) in which an individual responds to escalation with further escalation. Spiders with a large weight advantage over the opponent tend to escalate directly to threat and contact behavior (‘hawk’ strategy). The corresponding strategy for a much smaller visiting spider is immediate retreat (‘mouse’). A much smaller resident spider, however, will exhibit the ‘retaliator’ strategy to the ‘hawk’ rather than the more conservative ‘mouse’ strategy. The particular stategy exhibited, then, also depends on the energetic investment a particular individual has in the contended resource.
7.
Within functional group variability is shown to significantly affect the outcome of territorial disputes. Winning spiders exhibit an average of 20% less stereotypy than losing spiders. Unpredictable behavior possibly confuses the opponent, causing it to make inaccurate assessments of the weights of the opponent relative to it. Retreat follows. This behavior is linked to the ‘protean displays’ exhibited in defense against predators (Humphries and Driver, 1967).
262 citations