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: Body mass is sexually dimorphic and varies seasonally for all 5 species of prairie dogs (Sciuridae: Cynomys), as shown by data from live individuals over a period of 28 years (1974–2001).
Abstract: Body mass is sexually dimorphic and varies seasonally for all 5 species of prairie dogs (Sciuridae: Cynomys), as shown by data from live individuals over a period of 28 years (1974–2001; n = 16,447 body masses). Sexual dimorphism (i.e., body mass of males as percentage of body mass of females) during the breeding season is 105% for black-tailed prairie dogs, 127% for Utah prairie dogs, 131% for Gunnison's prairie dogs, and 136% for white-tailed prairie dogs. Sexual dimorphism is minimal at the end of the breeding season, when exhausted males are thin and early-breeding females are heavy with pregnancy. Sexual dimorphism is maximal at weaning, when rested, well-fed males are heavy and females are emaciated from lactation. The most likely ultimate causation for sexual dimorphism among prairie dogs is sexual selection.
42 citations
Cites background from "The Ecological Significance of Sexu..."
...Finally, sexual dimorphism might evolve in response to intersexual competition for food during the nonbreeding season (Amadon 1959; Peters and Grubb 1983; Schoener 1967; Temeles 1986)....
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TL;DR: The niche variation hypothesis attempts to explain biotic diversity at both genetic and phenetic levels, postulating a causal relationship between genetic or morphological variation and ecological habits.
Abstract: Evolutionary biology consists, in large measure, of attempts to understand biotic diversity. For this reason, the "niche variation" hypothesis (Van Valen, 1965) of adaptive variation occupies a central position among evolutionary theories. The hypothesis attempts to explain biotic diversity at both genetic and phenetic levels, postulating a causal relationship between genetic or morphological variation and ecological habits. Under the conditions of the hypothesis, populations that occupy broader ecological niches are expected to be more variable, in phenotype and genotype, than more narrow-niched populations (Van Valen, 1965). In the past, both continuous (unimodal) and discontinuous (polymorphic) variation have been considered as facets of a single process leading to adaptive variation. A variety of studies have examined the niche variation hypothesis. Tests of the hypothesis typically consist of estimates of genetic (i.e., electromorphic) or morphological variability in comparison with suitable estimates of ecological amplitude. In general, the results of these studies are ambivalent. While the electromorphic analyses of Shugart and Blaylock (1973) and Steiner (1977) generally support the niche variation model, others by Sabath (1974), Soule and Yang (1973), Powell and Wistrand (1978), Mitter and Futuyma (1979), and Smith (1981) provide conflicting, occasionally contradictory, results. Similarly, morphological analyses by Van Valen (1965), Grant et al. (1976), Davidson (1977, 1978), and Bernstein (1979) provide supporting evidence, while those of Soule and Stewart (1970), Soule (1972),
42 citations
41 citations
TL;DR: It is concluded that either interspecific competition does not affect the sexual size dimorphism of insular lizards and carnivores (i.e. character displacement and species sorting are rare in these taxa), or that the number of species in an assemblage or guild is a poor proxy for the intensity of inter specific competition in insular assemblages.
Abstract: 1. Sexual size dimorphism (SSD) can allow males and females of the same species to specialize
on different sized food items and therefore minimize intraspecific competition.
2. Interspecific competition, however, is thought to limit sexual dimorphism, as larger competitors
in the community will prevent the larger sex from evolving larger size, and smaller
species may prevent the smaller sex from becoming even smaller.
3. We tested this prediction using data on the sexual size dimorphism of lizards, and mammalian
carnivores, on islands world-wide.
4. Because insular communities are depauperate, and guilds are species-poor, it is often
assumed that enhanced sexual size dimorphism is common on islands. The intensity of interspecific
competition, hindering enhanced dimorphism, is thought to increase with competitor
richness.
5. We tested whether intraspecific sexual size dimorphism of mammalian carnivores and lizards
decreases with increasing island species richness. We further computed the average sexual
dimorphism of species on islands and tested whether species-rich islands are inhabited by relatively
monomorphic species. Within families and guilds across carnivores and lizards, and
with both intraspecific and interspecific approaches, we consistently failed to find support for
the notion that species-poor islands harbour more sexually dimorphic individuals or species.
6. We conclude that either interspecific competition does not affect the sexual size dimorphism
of insular lizards and carnivores (i.e. character displacement and species sorting are
rare in these taxa), or that the number of species in an assemblage or guild is a poor proxy
for the intensity of interspecific competition in insular assemblages.
40 citations
Cites background from "The Ecological Significance of Sexu..."
...…Dunstone 1985; Funston et al. 1998; Zielinski et al. 1999; McDonald 2002), but empirical support for its presence in lizards is equivocal (cf. e.g. Schoener 1967; Schoener, Slade & Stinson 1982; Shine 1989; Perry 1996; Herrel, Van Damme & De Vree 1996; Herrel et al. 1999; Kalboussi & Nouira 2004;…...
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TL;DR: The lizard Norops oxylophus used a variety of microhabitats distributed linearly along streams in southeastern Nicaragua, and body temperatures averaged 27.8 °C and lizards typically were in shade.
Abstract: The lizard Norops oxylophus used a variety of microhabitats distributed linearly along streams in southeastern Nicaragua. Body temperatures averaged 27.8 °C and lizards typically were in shade. Liz...
39 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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