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: The existence of habitat-specific sexual dimorphism suggests that adaptation of Anolis species to their environment is more complex than previously appreciated.
Abstract: Sexual size dimorphism (SSD) is the evolutionary result of selection operating differently on the body sizes of males and females. Anolis lizard species of the Greater Antilles have been classified into ecomorph classes, largely on the basis of their structural habitat (perch height and diameter). We show that the major ecomorph classes differ in degree of SSD. At least two SSD classes are supported: high SSD (trunk-crown, trunk-ground) and low SSD (trunk, crown-giant, grass-bush, twig). Differences cannot be attributed to an allometric increase of SSD with body size or to a phylogenetic effect. A third explanation, that selective pressures on male and/or female body size vary among habitat types, is examined by evaluating expectations from the major relevant kinds of selective pressures. Although no one kind of selective pressure produces expectations consistent with all of the information, competition with respect to structural habitat and sexual selection pressures are more likely possibilities than competition with respect to prey size or optimal feeding pressures. The existence of habitat-specific sexual dimorphism suggests that adaptation of Anolis species to their environment is more complex than previously appreciated.
226 citations
Cites background from "The Ecological Significance of Sexu..."
...Of those axes, perch diameter is the one most obviously related to body size and thus SSD; a within-species tendency for larger anoles to use thicker perches is well documented (Rand 1967b; Schoener 1967, 1968, 1970b; Schoener and Gorman 1968; Andrews 1971; Schoener and Schoener 1971a,b)....
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...Sexual differences in body size have wide ranging correlates in anoles, including differences in prey size (Schoener 1967, 1968; Schoener and Gorman 1968) and microhabitat use (Schoener 1967; Schoener and Schoener 1971a,b; Scott et al. 1976)....
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TL;DR: The hypothesis that interspecific competition has been the driving force behind the evolutionary radiation of Anolis lizards in the Caribbean is examined by examining the four lines of evidence supported by this hypothesis.
Abstract: Two approaches characterize the study of evolutionary ecology. Prospective studies investigate how present-day ecological processes may lead to evolutionary change; retrospective studies ask how present-day ecological conditions can be understood as the outcome of historical events. I argue that the most appropriate test of an evolutionary ecological hypothesis requires an integration of these approaches. I illustrate this approach by examining the hypothesis that interspecific competition has been the driving force behind the evolutionary radiation of Anolis lizards in the Caribbean. This hypothesis is supported by four lines of evidence: 1. Anole communities are structured by competition; 2. Populations alter resource use in the presence of congeners; 3. Microevolutionary adaptation occurs in response to resource shifts; and 4. Macroevolutionary patterns are consistent with interspecific competition as the driving force behind anole adaptive radiation.
210 citations
TL;DR: The patterns of body shape dimorphism in 15 species of Greater Antillean Anolis lizards are investigated and it is concluded that adaptive patterns differ for the sexes and that interspecific ecological variation is related more strongly to shape than to size for each sex.
Abstract: Sexual variation in body form is a common phenomenon in the natural world. Although most research has focused on dimorphism in size, examination of differences in shape can provide insight into ecological factors that may differ in importance to the sexes. In this study, we investigated the patterns of body shape dimorphism in 15 species of Greater Antillean Anolis lizards and investigated whether these patterns can be explained by allometry, phylogenetic effect, or sexual differences in habitat use. We found extensive shape and ecological variation between males and females. Previous studies have been conducted on males only; we found that females have also evolved morphologies to match their habitats. However, we concluded that adaptive patterns differ for the sexes and that interspecific ecological variation is related more strongly to shape than to size for each sex. Previous studies on males have revealed repeated convergent evolution of morphology to habitat types (termed ''ecomorphs''). Here, we found that ecomorphs also differ in the magnitude and direction of shape dimorphism. These results cannot be accounted for by allometric scaling or by phylogenetic similarity (regardless of assumptions regarding evo- lutionary process); they support previous studies that have found important life-history differences for species of different habitat types. We found some evidence for independent adaptation of the sexes, but with more complex ecological patterning occurring between sexes than can be explained by sexual selection alone. Consequently, some combination of functional differences and sexual selection is required.
210 citations
Cites background from "The Ecological Significance of Sexu..."
...Sex differences in ecology (food and/or habitat) associated with shape dimorphism are known from many reptiles (e.g., Schoener 1967, 1968, Schoener and Gorman 1968, Lister 1970, Schoener et al. 1982, Hebrard and Madsen 1984, Powell and Russell 1984, Shine 1991, Vitt et al. 1996), birds (e.g.,…...
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01 Jan 1986
TL;DR: The shorebirds (Charadriiformes: suborders Charadrii and Scolopaci) seem an ideal group for evaluating the role of natural and sexual selection in the evolution of sexual size dimorphism.
Abstract: The shorebirds (Charadriiformes: suborders Charadrii and Scolopaci) seem an ideal group for evaluating the role of natural and sexual selection in the evolution of sexual size dimorphism. Shorebirds exhibit a diverse range of size and plumage dimorphism that not only exceeds that found in other families of birds but virtually encompasses the range of variation found in the Class Aves. They include species in which males are the larger sex ( “normal dimorphism”), others in which sexual size differences are negligible, and still others in which the females are the larger sex (“reverse dimorphism”). Mating relationships include the entire range of possibilities: monogamy, polygyny, polyandry, and polygyny-polyandry. Some species are territorial, others nonterritorial; some are gregarious, others solitary; some have aerial displays, others do not; a few are even lekkers. Shorebirds forage for prey along rocky shores, fresh water or tidal mud and sand flats, pastures, grasslands, swamps, and forests, and in the air. Such diversity allows the sorting out of theories intended to explain the evolution of sexual size dimorphism.
203 citations
TL;DR: It is shown that sexual differences contribute substantially to the ecomorphological diversity produced by the adaptive radiations of West Indian Anolis lizards: within anole species, males and females occupy mostly non-overlapping parts of morphological space; the overall extent of sexual variation is large relative to interspecific variation; and the degree of variation depends on ecological type.
Abstract: A major task in biology is explaining patterns of biodiversity. Sexual differences in form are pervasive, yet factors promoting sexual dimorphism are rarely considered in studies of species diversity. Similarly, ecological and evolutionary factors governing community-level diversity are rarely invoked to explain the degree to which the sexes can differ. A study of the Anolis lizard, a classic example of adaptive radiation, with colonies on the islands of Cuba, Hispaniola, Jamaica and Puerto Rico, now shows that sexual differences are major contributors to morphological diversification in adaptive radiation. This suggests a model of how sexual dimorphism and adaptive radiation interact, a model that can be put to the test by observations of the native and introduced anoles in Florida. Sexual dimorphism has not been integrated into studies of adaptive radiation, despite the potential for the two sexes to occupy different niches. This paper reports that sexual differences contribute substantially to the ecomorphological diversity produced by the adaptive radiations of West Indian anolis lizards. Sexual dimorphism is widespread and substantial throughout the animal world1,2. It is surprising, then, that such a pervasive source of biological diversity has not been integrated into studies of adaptive radiation, despite extensive and growing attention to both phenomena1,3,4,5,6,7. Rather, most studies of adaptive radiation either group individuals without regard to sex or focus solely on one sex. Here we show that sexual differences contribute substantially to the ecomorphological diversity produced by the adaptive radiations of West Indian Anolis lizards: within anole species, males and females occupy mostly non-overlapping parts of morphological space; the overall extent of sexual variation is large relative to interspecific variation; and the degree of variation depends on ecological type. Thus, when sexual dimorphism in ecologically relevant traits is substantial, ignoring its contribution may significantly underestimate the adaptive component of evolutionary radiation. Conversely, if sexual dimorphism and interspecific divergence are alternative means of ecological diversification, then the degree of sexual dimorphism may be negatively related to the extent of adaptive radiation.
196 citations
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
129 citations
Book•
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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