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Journal ArticleDOI

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.
Citations
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Journal ArticleDOI
TL;DR: Using geometric morphometric analysis of head shape for 50 Anolis species, it is shown that two clades have converged on extreme levels of sexual dimorphism through similar, male‐specific changes in facial morphology.
Abstract: Studies integrating evolutionary and developmental analyses of morphological variation are of growing interest to biologists as they promise to shed fresh light on the mechanisms of morphological diversification. Sexually dimorphic traits tend to be incredibly divergent across taxa. Such diversification must arise through evolutionary modifications to sex differences during development. Nevertheless, few studies of dimorphism have attempted to synthesize evolutionary and developmental perspectives. Using geometric morphometric analysis of head shape for 50 Anolis species, we show that two clades have converged on extreme levels of sexual dimorphism through similar, male-specific changes in facial morphology. In both clades, males have evolved highly elongate faces whereas females retain faces of more moderate proportion. This convergence is accomplished using distinct developmental mechanisms; one clade evolved extreme dimorphism through the exaggeration of a widely shared, potentially ancestral, developmental strategy whereas the other clade evolved a novel developmental strategy not observed elsewhere in the genus. Together, our analyses indicate that both shared and derived features of development contribute to macroevolutionary patterns of morphological diversity among Anolis lizards.

73 citations


Cites methods from "The Ecological Significance of Sexu..."

  • ...DIMORPHISM IN SKULL SHAPE USING...

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  • ...Lizards are commonly used as models for studies of sexual dimorphism (e.g., Schoener 1967; Shine 1989; Zamudio 1998; Cox and John-Alder 2005, 2007; Cox and Calsbeek 2010)....

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Journal ArticleDOI
TL;DR: It is suggested that mate choice studies should account for multivariate effects of male traits, and also allow mate attraction to occur over variable spatial and temporal scales, paralleling mate choice under natural conditions.

73 citations

Journal ArticleDOI
01 Mar 1971-Ecology
TL;DR: It is hypothesized that the stereotypy of the Black-throated Green Warbler represents an adaptation to the extremely high density it experiences in large populations, which make up the major part of the gene pool.
Abstract: In this paper I attempt to answer the question, What (if any) differences occur in the foraging of isolated wood warblers (Parulidae) and ones in large multispecies populations? Parula (Parula americana), Myrtle (Dendroica coronata), and Black-throated Green (D. virens) Warblers were studied on seven small spruce-clad islands off the coast of Maine, each island supporting one pair of one to three of these species. Data obtained were compared with earlier studies of these species in large adjacent populations. Though seasonally isolated, all individuals belonged to the large gene pools of the appropriate species on the adjoining mainland. While the insular forests resemble those of the mainland, they are in general shorter and more open. When only one species was present, it was always the Parula Warbler; when two species were present, they were always the Parula and Myrtle. Black-throated Green Warblers only occurred in the presence of the latter two species. diversity increased as the size of forest and proportion of foliage in tree crowns grew. Parula and Myrtle Warblers experienced greater nesting success than Black-throated Green Warblers. Black-throated Green Warblers foraged much as they did in large populations; however, Myrtle and Parula Warblers demonstrated considerably more plasticity in foraging. When Black-throated Green Warblers were absent, the two other species tended to modify their foraging. On the one island studied in detail where only Parula Warblers occurred, they appeared to expand their foraging range farther than where Myrtle Warblers were present. Overlap in foraging usually decreased as species compositions became more depauperate. Though variability occurred among individuals of each species, variability of an individual in two different years appeared as great. Black-throated Green Warblers dominate the other two species socially, and the implications of this situation upon distributions in larger populations and on small islands are discussed. I hypothesize that the stereotypy of the Black-throated Green Warbler represents an adaptation to the extremely high density it experiences in large populations, which make up the major part of the gene pool. The higher degree of plasticity seen in Parula and Myrtle Warblers may be appropriate to their subordinate roles.

73 citations

Journal ArticleDOI
TL;DR: Dietary overlap approximated to 40% in all seasons except summer, when female predation upon lagomorphs reached a peak, and this reduction in intraspecific feeding competition was felt to be a valuable side-effect of body-size dimorphism.
Abstract: The diets of free-ranging male and female mink were sampled by analysing faeces collected from radio-tagged individuals. Significant sex differences were apparent in the predation upon three of the five principal prey groups. The larger males preyed much more heavily upon lagomorphs, the largest prey taken, while females preyed more upon fish and crustaceans than did males. These differences were consistent in each season except the autumn (September to November), when males preyed more heavily upon fish and crustacea than did females. Due to their large size, adult lagomorphs are felt to be relatively unavailable to female mink. Male mink are apparently large enough to specialize on lagomorphs, and male mink niche breadth was consistently lower than that of females. Dietary overlap approximated to 40% in all seasons except summer (68%), when female predation upon lagomorphs reached a peak. This reduction in intraspecific feeding competition was felt to be a valuable side-effect of body-size dimorphism.

73 citations

Journal ArticleDOI
TL;DR: It is argued that stabilimenta in the smallest spiders, in which typically two segments are opposed, so that they more or less “line up”, serve as camouflage, which supports an apparently-larger-size hypothesis, whereby intermediate-sized spiders in particular appear much larger than they actually are.
Abstract: A variety of orb-weaving spider species construct stabilimenta, patterned areas of dense silk, typically near the hub of the orb. The adaptive significance of this construction, along with associated behaviors such as shuttling and vibrating, is much debated. Arigiope argentata on small islands of the Bahamas frequently possess stabilimenta; we studied 397 individuals of this species to investigate possible functions of their stabilimenta, paying particular attention to predator-defense hypotheses. Cruciform stabilimenta were commoner in all size classes of spiders than discoid stabilimenta or no stabilimentum at all; discoid stabilimenta occurred mostly among intermediate size classes. Within the cruciform type, two-segmented stabilimenta were especially common among the very smallest spiders. Size of cruciform stabilimenta showed a curvilinear relation to spider body length; the fitted curve for “total segment length” had a maximum at an intermediate spider length. We argue that this relationship (among other phenomena) supports an apparently-larger-size hypothesis, whereby intermediate-sized spiders in particular appear much larger than they actually are. This could discourage predators, including those that are gape-limited such as lizards. We argue that stabilimenta in the smallest spiders, in which typically two segments are opposed, so that they more or less “line up”, serve as camouflage. When disturbed experimentally, spiders with discoid stabilimenta shuttle to the opposite side of the centrally located stabilimentum. This seems an obvious defensive behavior and occurs less frequently among spiders with cruciform stabilimenta. Large spiders vibrate more frequently than small ones, but no relation exists between vibration frequency and stabilimentum type. We argue (see also Tolbert 1975) that vibrating behavior, in which the spider can become a blur, renders its location more difficult to discern and the spider more difficult to grasp, rather than increasing apparent size.

73 citations

References
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292 citations

Journal ArticleDOI
01 Oct 1964-Ecology
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

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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