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Author |
Cameron, E.Z.; du Toit, J.T. |
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Title |
Winning by a neck: tall giraffes avoid competing with shorter browsers |
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Journal Article |
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Year |
2007 |
Publication |
The American naturalist |
Abbreviated Journal |
Am Nat |
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Volume |
169 |
Issue |
1 |
Pages |
130-135 |
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Keywords |
Acacia/growth & development; Animals; Feeding Behavior/*physiology; Neck/*anatomy & histology; Plant Leaves/growth & development; Ruminants/*anatomy & histology/*physiology; South Africa |
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Abstract |
With their vertically elongated body form, giraffes generally feed above the level of other browsers within the savanna browsing guild, despite having access to foliage at lower levels. They ingest more leaf mass per bite when foraging high in the tree, perhaps because smaller, more selective browsers deplete shoots at lower levels or because trees differentially allocate resources to promote shoot growth in the upper canopy. We erected exclosures around individual Acacia nigrescens trees in the greater Kruger ecosystem, South Africa. After a complete growing season, we found no differences in leaf biomass per shoot across height zones in excluded trees but significant differences in control trees. We conclude that giraffes preferentially browse at high levels in the canopy to avoid competition with smaller browsers. Our findings are analogous with those from studies of grazing guilds and demonstrate that resource partitioning can be driven by competition when smaller foragers displace larger foragers from shared resources. This provides the first experimental support for the classic evolutionary hypothesis that vertical elongation of the giraffe body is an outcome of competition within the browsing ungulate guild. |
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Mammal Research Institute, Department of Zoology and Entomology, University of Pretoria, Pretoria 0002, South Africa. ezcameron@zoology.up.ac.za |
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1537-5323 |
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PMID:17206591 |
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no |
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Call Number |
refbase @ user @ |
Serial |
410 |
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Author |
Flack, J.C.; de Waal, F.B.M.; Krakauer, D.C. |
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Title |
Social structure, robustness, and policing cost in a cognitively sophisticated species |
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Journal Article |
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Year |
2005 |
Publication |
The American Naturalist |
Abbreviated Journal |
Am Nat |
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Volume |
165 |
Issue |
5 |
Pages |
E126-139 |
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Keywords |
Animals; *Behavior, Animal; Cognition; Conflict (Psychology); Female; Macaca nemestrina/*physiology; Male; Models, Biological; *Social Behavior |
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Abstract |
Conflict management is one of the primary requirements for social complexity. Of the many forms of conflict management, one of the rarest and most interesting is third-party policing, or intervening impartially to control conflict. Third-party policing should be hard to evolve because policers personally pay a cost for intervening, while the benefits are diffused over the whole group. In this study we investigate the incidence and costs of policing in a primate society. We report quantitative evidence of non-kin policing in the nonhuman primate, the pigtailed macaque. We find that policing is effective at reducing the intensity of or terminating conflict when performed by the most powerful individuals. We define a measure, social power consensus, that predicts effective low-cost interventions by powerful individuals and ineffective, relatively costly interventions by low-power individuals. Finally, we develop a simple probabilistic model to explore whether the degree to which policing can effectively reduce the societal cost of conflict is dependent on variance in the distribution of power. Our data and simple model suggest that third-party policing effectiveness and cost are dependent on power structure and might emerge only in societies with high variance in power. |
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Santa Fe Institute, Santa Fe, New Mexico 87501, USA. jflack@santafe.edu |
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1537-5323 |
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PMID:15795848 |
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refbase @ user @ |
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168 |
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Author |
Uehara, T.; Yokomizo, H.; Iwasa, Y. |
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Title |
Mate-choice copying as Bayesian decision making |
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Journal Article |
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Year |
2005 |
Publication |
The American naturalist |
Abbreviated Journal |
Am Nat |
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Volume |
165 |
Issue |
3 |
Pages |
403-410 |
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Keywords |
Animals; *Bayes Theorem; *Choice Behavior; Female; Male; *Models, Biological; *Sexual Behavior, Animal |
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Abstract |
Mate-choice copying by females has been reported in fishes (e.g., guppies) and lekking birds. Presumably, females assess males' quality using both information from direct observation of males and information acquired by observing other females' choices. Here, we study mathematically the conditions under which mate-choice copying is advantageous on the basis of Bayesian decision theory. A female may observe the mate choice of another female, called the model female, who has performed an optimal choice based on her own judgment. The conditions required for the focal female to choose the same mate as that chosen by the model female should depend on the male's appearance to her, the reliability of her own judgment of male quality, and the reliability of the model females. When three or more females are involved, the optimal mate choice critically depends on whether multiple model females make decisions independently or they themselves copy the choices of others. If two equally reliable females choose different males, the choice of the second female, made knowing the choice of the first, should have a stronger effect on the choice of the third (focal) female. This “last-choice precedence” should be tested experimentally. |
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Department of Biology, Faculty of Sciences, Kyushu University, Fukuoka 812-8581, Japan. uehara@bio-math.biology.kyushu-u.ac.jp |
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1537-5323 |
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PMID:15729669 |
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no |
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Serial |
1821 |
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Author |
Larose, C.; Richard-Yris, M.-A.; Hausberger, M.; Rogers, L.J. |
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Title |
Laterality of horses associated with emotionality in novel situations |
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Journal Article |
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Year |
2006 |
Publication |
Laterality |
Abbreviated Journal |
Laterality |
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Volume |
11 |
Issue |
4 |
Pages |
355-367 |
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Keywords |
Affect/*physiology; Animals; Brain/*physiology; Female; Functional Laterality/*physiology; Horses; Male; *Social Behavior; *Social Environment |
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Abstract |
We have established that lateral biases are characteristic of visual behaviour in 65 horses. Two breeds, Trotters and French Saddlebreds aged 2 to 3, were tested on a novel object test. The main finding was a significant correlation between emotionality index and the eye preferred to view the novel stimulus: the higher the emotionality, the more likely that the horse looked with its left eye. The less emotive French Saddlebreds, however, tended to glance at the object using the right eye, a tendency that was not found in the Trotters, although the emotive index was the same for both breeds. The youngest French Saddlebreds did not show this trend. These results are discussed in relation to the different training practices for the breeds and broader findings on lateralisation in different species. |
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Universite de Rennes 1, France |
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1357-650X |
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Notes |
PMID:16754236 |
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no |
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Call Number |
Equine Behaviour @ team @ room B 3.029 |
Serial |
1826 |
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Author |
Henderson, A.J.Z. |
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Title |
Don't fence me in: managing psychological well being for elite performance horses |
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Journal Article |
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Year |
2007 |
Publication |
Journal of Applied Animal Welfare Science : JAAWS |
Abbreviated Journal |
J. Appl. Anim. Welf. Sci. |
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Volume |
10 |
Issue |
4 |
Pages |
309-329 |
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Keywords |
*Animal Husbandry; Animal Welfare; Animals; *Behavior, Animal; Horses/*psychology; *Physical Conditioning, Animal; *Stereotyped Behavior |
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This article posits that stereotypical behavior patterns and the overall psychological well being of today's performance horse could be substantially enhanced with care that acknowledges the relationship between domesticated horses and their forerunners. Feral horses typically roam in stable, social groups over large grazing territories, spending 16-20 hr per day foraging on mid- to poor-quality roughage. In contrast, today's elite show horses live in relatively small stalls, eat a limited-but rich-diet at specific feedings, and typically live in social isolation. Although the horse has been domesticated for more than 6000 years, there has been no selection for an equid who no longer requires an outlet for these natural behaviors. Using equine stereotypies as a welfare indicator, this researcher proposes that the psychological well being of today's performance horse is compromised. Furthermore, the article illustrates how minimal management changes can enhance horses' well being while still remaining compatible with the requirements of the sport-horse industry. The article discusses conclusions in terms of Fraser, Weary, Pajor, and Milligan's “integrative welfare model” (1997). |
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Department of Psychology, Simon Fraser University, Burnaby, British Columbia, Canada. zamoyska@shaw.ca |
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1088-8705 |
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PMID:17970632 |
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no |
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Equine Behaviour @ team @ |
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4363 |
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Author |
Johnstone, R.A. |
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Title |
Eavesdropping and animal conflict |
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Journal Article |
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Year |
2001 |
Publication |
Proceedings of the National Academy of Sciences of the United States of America |
Abbreviated Journal |
Proc. Natl. Acad. Sci. U.S.A. |
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Volume |
98 |
Issue |
16 |
Pages |
9177-9180 |
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Keywords |
*Aggression; Animals; *Behavior, Animal; *Conflict (Psychology); Models, Theoretical |
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Abstract |
Fights between pairs of animals frequently take place within a wider social context. The displays exchanged during conflict, and the outcome of an encounter, are often detectable by individuals who are not immediately involved. In at least some species, such bystanders are known to eavesdrop on contests between others, and to modify their behavior toward the contestants in response to the observed interaction. Here, I extend Maynard Smith's well known model of animal aggression, the Hawk-Dove game, to incorporate the possibility of eavesdroppers. I show that some eavesdropping is favored whenever the cost of losing an escalated fight exceeds the value of the contested resource, and that its equilibrium frequency is greatest when costs are relatively high. Eavesdropping reduces the risk of escalated conflict relative to that expected by chance, given the level of aggression in the population. However, it also promotes increased aggression, because it enhances the value of victory. The net result is that escalated conflicts are predicted to occur more frequently when eavesdropping is possible. |
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Department of Zoology, University of Cambridge, Downing Street, Cambridge CB2 3EJ, United Kingdom. raj1003@hermes.cam.ac.uk |
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0027-8424 |
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PMID:11459936 |
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no |
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Call Number |
refbase @ user @ |
Serial |
497 |
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Author |
Chase, I.D.; Tovey, C.; Spangler-Martin, D.; Manfredonia, M. |
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Title |
Individual differences versus social dynamics in the formation of animal dominance hierarchies |
Type |
Journal Article |
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Year |
2002 |
Publication |
Proceedings of the National Academy of Sciences of the United States of America |
Abbreviated Journal |
Proc. Natl. Acad. Sci. U.S.A. |
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Volume |
99 |
Issue |
8 |
Pages |
5744-5749 |
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Keywords |
Animals; *Behavior, Animal; Fishes; Humans; *Social Behavior; *Social Dominance |
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Abstract |
Linear hierarchies, the classical pecking-order structures, are formed readily in both nature and the laboratory in a great range of species including humans. However, the probability of getting linear structures by chance alone is quite low. In this paper we investigate the two hypotheses that are proposed most often to explain linear hierarchies: they are predetermined by differences in the attributes of animals, or they are produced by the dynamics of social interaction, i.e., they are self-organizing. We evaluate these hypotheses using cichlid fish as model animals, and although differences in attributes play a significant part, we find that social interaction is necessary for high proportions of groups with linear hierarchies. Our results suggest that dominance hierarchy formation is a much richer and more complex phenomenon than previously thought, and we explore the implications of these results for evolutionary biology, the social sciences, and the use of animal models in understanding human social organization. |
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Department of Sociology, State University of New York, Stony Brook, NY 11794-4356, USA. Ichase@notes.cc.sunysb.edu |
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0027-8424 |
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PMID:11960030 |
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no |
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Call Number |
refbase @ user @ |
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442 |
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Author |
Reader, S.M.; Laland, K.N. |
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Title |
Social intelligence, innovation, and enhanced brain size in primates |
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Journal Article |
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Year |
2002 |
Publication |
Proceedings of the National Academy of Sciences of the United States of America |
Abbreviated Journal |
Proc. Natl. Acad. Sci. U.S.A. |
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Volume |
99 |
Issue |
7 |
Pages |
4436-4441 |
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Keywords |
Animals; Brain/*anatomy & histology; Evolution; *Intelligence; Learning; Primates/*anatomy & histology/*psychology; Social Behavior |
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Abstract |
Despite considerable current interest in the evolution of intelligence, the intuitively appealing notion that brain volume and “intelligence” are linked remains untested. Here, we use ecologically relevant measures of cognitive ability, the reported incidence of behavioral innovation, social learning, and tool use, to show that brain size and cognitive capacity are indeed correlated. A comparative analysis of 533 instances of innovation, 445 observations of social learning, and 607 episodes of tool use established that social learning, innovation, and tool use frequencies are positively correlated with species' relative and absolute “executive” brain volumes, after controlling for phylogeny and research effort. Moreover, innovation and social learning frequencies covary across species, in conflict with the view that there is an evolutionary tradeoff between reliance on individual experience and social cues. These findings provide an empirical link between behavioral innovation, social learning capacities, and brain size in mammals. The ability to learn from others, invent new behaviors, and use tools may have played pivotal roles in primate brain evolution. |
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Department of Zoology, University of Cambridge, High Street, Madingley, Cambridge CB3 8AA, United Kingdom |
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0027-8424 |
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PMID:11891325 |
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no |
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2149 |
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Author |
Plotnik, J.M.; de Waal, F.B.M.; Reiss, D. |
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Title |
Self-recognition in an Asian elephant |
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Journal Article |
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Year |
2006 |
Publication |
Proceedings of the National Academy of Sciences of the United States of America |
Abbreviated Journal |
Proc. Natl. Acad. Sci. U.S.A. |
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Volume |
103 |
Issue |
45 |
Pages |
17053-17057 |
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Animals; Asia; *Behavior, Animal; Cognition; Elephants/*psychology; Female; Photic Stimulation |
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Abstract |
Considered an indicator of self-awareness, mirror self-recognition (MSR) has long seemed limited to humans and apes. In both phylogeny and human ontogeny, MSR is thought to correlate with higher forms of empathy and altruistic behavior. Apart from humans and apes, dolphins and elephants are also known for such capacities. After the recent discovery of MSR in dolphins (Tursiops truncatus), elephants thus were the next logical candidate species. We exposed three Asian elephants (Elephas maximus) to a large mirror to investigate their responses. Animals that possess MSR typically progress through four stages of behavior when facing a mirror: (i) social responses, (ii) physical inspection (e.g., looking behind the mirror), (iii) repetitive mirror-testing behavior, and (iv) realization of seeing themselves. Visible marks and invisible sham-marks were applied to the elephants' heads to test whether they would pass the litmus “mark test” for MSR in which an individual spontaneously uses a mirror to touch an otherwise imperceptible mark on its own body. Here, we report a successful MSR elephant study and report striking parallels in the progression of responses to mirrors among apes, dolphins, and elephants. These parallels suggest convergent cognitive evolution most likely related to complex sociality and cooperation. |
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Living Links, Yerkes National Primate Research Center, and Department of Psychology, Emory University, 532 North Kligo Circle, Atlanta, GA 30322, USA |
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0027-8424 |
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PMID:17075063 |
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refbase @ user @ |
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408 |
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Author |
Scheffer, M.; van Nes, E.H. |
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Title |
Self-organized similarity, the evolutionary emergence of groups of similar species |
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Journal Article |
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Year |
2006 |
Publication |
Proceedings of the National Academy of Sciences of the United States of America |
Abbreviated Journal |
Proc. Natl. Acad. Sci. U.S.A. |
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Volume |
103 |
Issue |
16 |
Pages |
6230-6235 |
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Animals; *Competitive Behavior; *Ecosystem; *Evolution; *Models, Biological |
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Ecologists have long been puzzled by the fact that there are so many similar species in nature. Here we show that self-organized clusters of look-a-likes may emerge spontaneously from coevolution of competitors. The explanation is that there are two alternative ways to survive together: being sufficiently different or being sufficiently similar. Using a model based on classical competition theory, we demonstrate a tendency for evolutionary emergence of regularly spaced lumps of similar species along a niche axis. Indeed, such lumpy patterns are commonly observed in size distributions of organisms ranging from algae, zooplankton, and beetles to birds and mammals, and could not be well explained by earlier theory. Our results suggest that these patterns may represent self-constructed niches emerging from competitive interactions. A corollary of our findings is that, whereas in species-poor communities sympatric speciation and invasion of open niches is possible, species-saturated communities may be characterized by convergent evolution and invasion by look-a-likes. |
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Aquatic Ecology and Water Quality Management Group, Department of Environmental Sciences, Wageningen University, P.O. Box 8080, 6700 DD, Wageningen, The Netherlands. marten.scheffer@wur.nl |
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0027-8424 |
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PMID:16585519 |
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refbase @ user @ |
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510 |
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