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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Dissertation•
17 Dec 2014
TL;DR: A phylogenetically controlled comparative approach found that majors of seedassociated Pheidole do not have larger heads than do majors of non-seedharvesting species, but there is a positive relationship between seed-Harvesting and minor head length, suggesting head size of major and minor subcastes can evolve for diet specialization, but they do so relative to the morphology of other worker castes.
Abstract: An organism’s morphology is constrained by evolutionary history and the need of the organism to meet a variety of, and potentially competing, functions. The ant genus Pheidole is presently the most species-rich of the 324 described ant genera. Workers of Pheidole are almost always dimorphic, comprising a small minor subcaste and a major or soldier subcaste with a distinctively large head. This separation of workers into two distinct subcastes makes Pheidole an ideal genus to address questions on the evolution of morphology in relation to ecological specialization. Major workers can perform a variety of tasks, but they are usually specialized for defense and the retrieval and processing of food. Pheidole species vary in their diet but many species gather seeds and the majors are known to mill the seeds using the large jaws powered by mandible closer muscles that fill the head cavity. I examined the relationship between seedharvesting and head size, hypothesizing that seed harvesters have majors with larger heads compared to non-seed-harvesting species to accommodate more powerful mandibular muscles. By taking a phylogenetically controlled comparative approach, I found that majors of seedassociated Pheidole do not have larger heads (width and length) than do majors of non-seedharvesting species, but there is a positive relationship between seed-harvesting and minor head length. Additionally, there is a significant relationship of head width and length to seedharvesting when examining the difference in size of minors relative to majors within species. Seed-harvesting Pheidole species have smaller minors and larger majors than their non-seedharvesting congeners. This finding suggests that head size of major and minor subcastes can evolve for diet specialization, but they do so relative to the morphology of other worker castes.
3 citations
Cites background from "The Ecological Significance of Sexu..."
...(Selander, 1966; Schoener, 1967; Shine, 1989), and may be driven by sex specific reproductive or dispersal strategies (Greenwood, 1980; Harrison, 1980; Pusey, 1987)....
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...…selection and the elaboration of secondary sexual characteristics (Darwin, 1874), can reduce intra-specific competition for resources (Selander, 1966; Schoener, 1967; Shine, 1989), and may be driven by sex specific reproductive or dispersal strategies (Greenwood, 1980; Harrison, 1980; Pusey, 1987)....
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TL;DR: This work aims at elucidating the proximate mechanisms of sexual dimorphism in head and limb shape, performance and dewlap size in Anolis baracoae, a crown-giant anole, and hypothesizes that, whereas selection favors a similar head and limbs shape in males and females, selection pressures on dew Lap size and bite performance likely differ between the sexes.
Abstract: Sexual dimorphism may be indicative of differential natural and/or sexual selection pressures acting on males and females. Although similar degrees of adult sexual dimorphism may be observed among populations and species, underlying physiological, developmental and ecological processes driving growth during the juvenile stages may vary. Unraveling how and when differences arise during ontogeny is important to our understanding of the evolutionary patterns observed among adults. In addition, growth patterns may differ among traits within a single individual. Anolis lizards vary greatly in the degree of adult sexual size and shape dimorphism. Ultimate hypotheses (e.g. sexual selection, habitat partitioning) have been put forward to explain this variation, but proximate mechanisms operating during the juvenile stages remain largely unknown. Herein, we aim at elucidating the proximate mechanisms of sexual dimorphism in head and limb shape, performance and dewlap size in Anolis baracoae, a crown-giant anole. We used a longitudinal approach and raised 23 captive-bred juvenile A. baracoae lizards through adulthood. By quantifying body size, head and limb dimensions, dewlap size and bite performance, we obtained growth trajectories that were compared between the sexes and among traits. Our results show that the growth of head and limb shape is similar in males and females, whereas dewlap size and bite performance diverge at a specific age. Based on these results, we hypothesize that, whereas selection favors a similar head and limb shape in males and females, selection pressures on dewlap size and bite performance likely differ between the sexes. In addition, dewlap size starts diverging around the time the animals reach sexual maturity, whereas bite performance diverges much earlier in (sexually) immature males.
3 citations
Cites background from "The Ecological Significance of Sexu..."
...…before reaching sexual maturity) may be related to a sexual difference in ecological factors, such as diet, to avoid intersexual competition over limited resources between subadult males and females (Schoener, 1967; Herrel et al., 2006; Vanhooydonck et al., 2010; Lopez-Darias et al., in press)....
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TL;DR: The diet of Ameiva edracantha Bocourt 1874, a terrestrial diurnal teiid lizard distributed in northwestern Peru and southwestern Ecuador is described for the first time and parameters such as profitability and prey target selection could be involved in prey selection by A. edracanth.
Abstract: The diet of Ameiva edracantha Bocourt 1874, a terrestrial diurnal teiid lizard distributed in northwestern Peru and southwestern Ecuador is described for the first time. Stomach contents of fifteen individuals collected from quebrada La Angostura were analyzed. Lepidopteran larvae, coleopterans, orthopterans and spiders were the dominant preys in the lizard’s diet. Snout-vent length and head length, width and height were not correlated to prey length, width and volume. Other parameters such as profitability and prey target selection could be involved in prey selection by A. edracantha.
3 citations
01 Jan 2012
TL;DR: Investigation of occurrence of sexual size dimorphism (SSD) in a popula- tion of Rana (Pelophylax) ridibunda ridIBunda Pallas, 1771 from Darre-Shahr Township, Ilam Prov- ince, western Iran showed considerable differences between sexes.
Abstract: In this survey we investigated occurrence of sexual size dimorphism (SSD), in a popula- tion of Rana (Pelophylax) ridibunda ridibunda Pallas, 1771 from Darre-Shahr Township, Ilam Prov- ince, western Iran. Ninety-six specimens (52 females and 44 males) were captured, measured and released into their natural habitat. Twelve metric characters were measured by digital calipers to the nearest 0.01 mm. Statistical analyses showed considerable differences between sexes for mea- sured characters. The largest female and male were 89.55 and 73.16 mm SVL, respectively, while the smallest female and male were 68.52 and 61.65 mm SVL, respectively. SPSS version 16 was used for running the analysis. The Independent-Sample t-test (2-tailed) showed that each character has sig- nificant differences between the sexes ( p ≤ 0.01), and for each variable the female value was larger than for males on average.
3 citations
Cites background from "The Ecological Significance of Sexu..."
...Different factors can influence sexual dimorphism including female reproductive strategy (Tinkle et al. 1970; Verrastro 2004), sexual selection (Carothers 1984; Verrastro 2004), and competition for food resources (Schoener 1967; Verrastro 2004)....
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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
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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