The Ecological Significance of Sexual Dimorphism in Size in the Lizard Anolis conspersus.
27 Jan 1967-Science (American Association for the Advancement of Science)-Vol. 155, Iss: 3761, pp 474-477
TL;DR: Anolis conspersus selects prey from a wide range of taxa and shows no obvious intraspecific specialization not connected to differences in microhabitat and prey size.
Abstract: Adult males of Anolis conspersus capture prey of significantly larger size and occupy perches of significantly greater diameter and height than do adult females; similarly, these three dimensions of the niche are significantly larger for adult females than for juveniles. Adult males on the average eat a smaller number of prey, and the range in size of prey is larger. The relationship between the average length of the prey and that of the predator is linear when the predator size is above 36 millimeters, but becomes asymptotic when it is below that value. Subadult males as long as adult females eat significantly larger food than do the latter, but only in the larger lizards is this correlated with a relatively larger head. Anolis conspersus selects prey from a wide range of taxa and shows no obvious intraspecific specialization not connected to differences in microhabitat and prey size. The efficiency of this system for solitary species is pointed out.
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TL;DR: It is demonstrated that both exaptation and adaptation have produced convergent similarity in different size-related characters of solitary island lizards, and suggested that convergent phenomena may require historical explanations that are ecological as well as evolutionary.
Abstract: Independent evolutionary lineages often display similar characteristics in comparable environments. Three kinds of historical hypotheses could explain this convergence. The first is adaptive and evolutionary: nonrandom patterns may result from analogous evolutionary responses to shared conditions. The second explanation is exaptive and ecological: species may be filtered by their suitability for a particular type of environment. The third potential explanation is a null hypothesis of random colonization from a historically nonrandom source pool. Here we demonstrate that both exaptation and adaptation have produced convergent similarity in different size-related characters of solitary island lizards. Large sexual size dimorphism results from adaptive response to solitary existence; uniform, intermediate size results from ecological filtering of potential colonizers. These results demonstrate the existence of deterministic exaptive convergence and suggest that convergent phenomena may require historical explanations that are ecological as well as evolutionary.
33 citations
Cites background from "The Ecological Significance of Sexu..."
...Intermediate size evolves in response to local competition in multispecies communities (Losos 1994), but later is advantageous for solitary existence (Schoener 1967)....
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...…greater sexual size dimorphism (SSD; allowing intraspecific partitioning of resources) and uniform (i.e. energetically efficient) body sizes have been documented in many solitary species (e.g. birds: Selander 1966, Clegg & Owens 2002; mammals: Dayan & Simberloff1998; lizards:Schoener1967,1969a,b)....
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...Following solitary colonization, greater SSD should minimize competition between sexes (Schoener 1967), and both sexual selection and intrasexual competition for resources may shape SSD in the absence of competitive congeners....
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...Although these patterns are widely accepted and ecological and energetic explanations have been offered (Schoener 1967, 1969b; Case 1978; Naganuma & Roughgarden 1990), the evolutionary bases for these patterns are poorly understood....
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TL;DR: A recent field study of woolly spider monkeys shows that these large primates are characterized by apolygynous mating system, which supports the view that a lack of canine tooth dimorphism in an anthropoid species does not necessarily imply either a monogamous, pair-bonded mating system or male parental care.
Abstract: The relatively low degree of canine tooth dimorphism in Australopithecus afarensis has been used as “primary evidence” to support the concept of a mating system of monogamous pair-bonding and male provisioning. A recent field study of woolly spider monkeys shows that these large primates, which lack canine tooth (and body size) dimorphism, are characterized by apolygynous mating system. Male parental care of infants is absent in this species. These data support the view that a lack of canine tooth dimorphism in an anthropoid species does not necessarily imply either a monogamous, pair-bonded mating system or male parental care.
32 citations
32 citations
TL;DR: The intent of this paper is to critically evaluate the roles of the reproductive and phenetic species concepts, and to propose a generalized procedure for delimiting species units, which incorporates ecological as well as reproductive and Phenetic information.
Abstract: Doyen, J. T., and C. N. Slobodchikoff (Division of Entomology and Parasitology, University of California, Berkeley, Cal. 94720 and Department of Biology, Northern Arizona University, Flagstaff, Ariz. 86001) 1974. An operational approach to species classification. Syst. Zool. 23:239-247.-Operational biological classification at the species level is analyzed as a series of sequential steps employing phenetic, reproductive, and ecological parameters. The first step involves segregation of individuals or populations into phenetically similar groups. Numerical techniques for objectively assessing phenetic similarities are well established, and are the method of choice. The next major step involves reproductive grouping, whenever possible. Reproductive isolation may be a sufficient criterion for species status in the case of sympatric populations. In other cases species decisions are usually deferred until the following step, or ecological grouping, which is based on ecological similarities and differences, quantified and analyzed with numerical methods. Species limits may be visualized graphically by considering phenetic, ecological, and reproductive similarities as axes of a three dimensional space. Populations may be plotted within this space and may be tested for conspecific status by existing computer techniques. [Numerical taxonomy; species determination.] Species are groups of populations placed in the same taxonomic category. The commonest criteria used in defining species groupings are reproductive (or biological) and phenetic. While both criteria are vigorously defended by their proponents, neither has been entirely satisfactory in defining taxonomic species. We believe that the species is an idealized concept, and that different groups of biological populations only approximate the ideal. Just as the behavior of gases is idealized in theory, with no actual gas having exactly the requisite properties, so also are groups of populations of organisms idealized as species units, with few such groups, if any, having all the properties of idealized species. The primary value of grouping populations into species is utility. It is convenient to deal with units larger than local populations, even though these units may not accurately reflect the evolutionary changes occurring within populations. Organizing biologically similar populations into larger groups allows generalized statements to be made without the cumbersome necessity of defining each population. At the same time, the human need for a simple answer to the question, "What is that organism?" is satisfied. The intent of this paper is to critically evaluate the roles of the reproductive and phenetic species concepts, and to propose a generalized procedure for delimiting species units. This procedure incorporates ecological as well as reproductive and phenetic information. A simple graphic model is used to illustrate one way in which the method might be applied. A simple statement of the biological species definition is that of Mayr (1969a): "Species are groups of interbreeding natural populations that are reproductively isolated from other such groups." The sole criterion delimiting species in this definition is reproductive isolation (Mayr, 1969b). If two populations interbreed they are the same species; if they cannot interbreed they are different species. Although the idea of defining all species on the basis of a single characteristic is very attractive, the biological species definition suffers several difficulties which have been pointed out frequently in the recent literature. Pheneticists object to the biological spe-
32 citations
TL;DR: The relationship between jaw size in Anolis lizards and properties of the local insect fauna was examined in solitary populations on islands in the Grenadines and within the island of Dominica and showed that average lizard size in adult males is strongly correlated with local insect abundance.
Abstract: The relationship between jaw size in Anolis lizards and properties of the local insect fauna was examined in solitary populations on islands in the Grenadines and within the island of Dominica. It was found that average lizard size in adult males is strongly correlated with local insect abundance. Adult females show a weaker correlation. There was no discernible relation between average lizard size and average insect size in the environment. The spatial scale of geographical variation in lizard size was quantified with the variance spectrum and the variance transfer function. It was found that large gradients in average lizard size occur over less than 100 m, and that the spatial pattern of lizard size strongly tracks patches of insect abundance occupying 60 m in length. The data are relevant to explaining discrepancies in the parallel evolution of a characteristic body size in solitary populations of Anolis. The data show that some, and imply strongly that all but one, of the discrepancies in parallel evolution are explained by the presence of an unusually high local productivity.
32 citations
Cites methods from "The Ecological Significance of Sexu..."
...According to Schoener's (1969) foraging model, larger animals should be more sensitive to productivity changes than smaller ones because larger animals are using prey from the tail of the abundance vs size distribution....
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References
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TL;DR: The eight species of the genus Anolis in Puerto Rico can be divided into four morphological similarities as discussed by the authors : perch height, perch diameter, high-shade preference and low-shading preference.
Abstract: The eight species of lizards of the genus Anolis in Puerto Rico can be divided into four morphological similarities. One, Anolis curvieri, is very different from the rest and has not been discussed here. The other seven species fall into three groups. Each of these groups occupies a different structural habitat which can be defined in terms of perch height and perch diameter. Within each of these three groups the species have very similar but not indential structural habitats but differ very widely in climatic habitat defined in terms of shade. Shade preferences seem to result from the temperature preferences of the species involved. In each group there is one species with high shade preference which is essentially restricted to the mountains. Each group also has a species with a lower shade preference which occurs in the lowlands and extends up into the mountains in exposed or sunny situations. One of the three groups has an additional species which is restricted to the hot and southwest corner of Puerto Rico. When one compares the temperature preferences or eccritic temperatures of the various species, one finds in each group that the highland species has a lower eccritic temperature than does the lowland species. There is little temperature difference between the lowland species and arid southwest species in the group where this additional third species is present. The species within each structural habitat show many morphological similarities which may be the result of their being closely related or may be the result of adaptation to similar environments. The differences in microhabitat between the Puerto Rican anoles separate them spatially though not completely. In species occupying different structural habitats in the same area the overlap may involve part of the home range of most of the individuals in the area. In species occupying the same structural but different climatic habitats the overlap may involve all of the home range of some individuals but of only a small fraction of the individuals in the total population. The spatial separation among Puerto Rican Anolis can be suggested to be of ecological significance because it reduces interspecific competition and because it allows the various species to adapt more precisely to different parts of the available habitat. Thus members of a genus may exploit the habitat more efficiently.
218 citations
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01 Jan 1964
TL;DR: The life of the rainbow lizard , The life of a rainbow lizard, مرکز فناوری اطلاعات £1,000,000 ($2,000; £1,500,000)
Abstract: The life of the rainbow lizard , The life of the rainbow lizard , مرکز فناوری اطلاعات و اطلاع رسانی کشاورزی
119 citations
"The Ecological Significance of Sexu..." refers background in this paper
...On the basis of essentially the same pattern of staining, other investigators have reached the same conclusion (3, 4), or have attributed staining additionally or alternatively to the processes of the bipolar cells (5, 6), the ganglion cells (4, 5), or centrifugal fibers from the optic nerve (7)....
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...A greater proportion of large insects were found in larger adult males than in adult females of Anolis lineatopus and Agama agama (4, 5); similarly, juveniles take smaller food than adults (5-7)....
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