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: In this paper, the authors investigate why and when sexual dimorphism might fail to evolve even if genetic covariation between the sexes posed no constraint, and explore broader conditions, including multiple resources with habitat heterogeneity, genetic correlations, and non-Gaussian resource use efficiency functions.
Abstract: 1. Sexes often differ more obviously in secondary sexual characteristics than in traits that appear naturally selected, despite conceivable benefits to intersexual niche partitioning. Genetic constraints may play a role in limiting sex‐specific niche evolution, however it is not clear why this limit should apply to naturally selected traits more than those under sexual selection; the latter routinely produces dimorphism. We ask whether ecological factors and/or features of the mating system limit dimorphism in resource use, or conversely, what conditions are the most permissible ones for sexual niche differences.
2. The scale of mating competition and spatial variation in resource availability can help predict sexually dimorphic niches or the lack thereof. We investigate why and when dimorphism might fail to evolve even if genetic covariation between the sexes posed no constraint.
3. Our analytical model incorporates the first aspect of spatial interactions (scale of mating competition). It is followed by simulations that explore broader conditions, including multiple resources with habitat heterogeneity, genetic correlations, and non‐Gaussian resource use efficiency functions.
4. We recover earlier known conditions for favourable conditions for the evolution of niche partitioning between sexes, such as narrow individual niche and low degrees of genetic constraint. We also show spatial considerations to alter this picture. Sexual niche divergence occurs more readily when local mating groups are small and different resources occur reliably across habitats. Polygyny (medium‐sized or large mating groups) can diminish the prospects for dimorphism even if no genetic constraints are present. Habitat heterogeneity typically also disfavours niche dimorphism, but can also lead to polymorphism within a sex, if it is beneficial to specialise to be very competitive in one habitat, even at a cost to performance in the other.
5. Sexual conflict is usually used to explain dimorphic traits or behaviours. Our models highlight that introducing conflict (achieved by switching from monogamy to polygamy) can also be responsible for sexual monomorphism. Under monogamy, males benefit from specialising to consume other resources than what feeds the female best. Polygyny makes males disregard this female benefit, and both sexes compete for the most profitable resource, leading to overlapping niches.
12 citations
TL;DR: Sexual conflict can explain why adaptive TGP evolves in some species but not others, why sons and daughters respond to parental signals in different ways, and why complex patterns of sex-specific TGP may often be non-adaptive.
Abstract: Transgenerational plasticity (TGP) occurs when the environment experienced by parents induces changes in offspring traits. Such effects can be adaptive or non-adaptive and are increasingly recognised as key determinants of health, cognition, development and performance across a wide range of taxa, including humans. While the conditions that favour maternal TGP are well understood, rapidly accumulating evidence indicates that TGP can be maternal or paternal, and offspring responses can be sex-specific. However, the evolutionary mechanisms that drive this diversity are unknown. Here we use individual-based models to show that diverse patterns of TGP can evolve when the sexes experience different environments. We find that non-adaptive patterns of TGP result when alleles at loci that determine offspring responses to environmental information originating from the mother and father are subject to sexually antagonistic selection. By contrast, a variety of sex-specific responses evolve via duplication and sex-limitation of loci responsive to parental information, including non-adaptive TGP when sexual selection is strong. Sexual conflict can therefore explain why adaptive TGP evolves in some species but not others, why sons and daughters respond to parental signals in different ways, and why complex patterns of sex-specific TGP may often be non-adaptive.
12 citations
Journal Article•
TL;DR: Results indicate that body size and population structure vary across a geographic gradient; turtles from the Pascagoula River site were generally larger relative to two upstream sites on two tributaries, the Leaf and Chickasawhay rivers.
Abstract: Graptemys flavimaculata (Yellow-blotched Sawback) is a small, highly aquatic turtle that is endemic to rivers and large creeks of the Pascagoula River system of southeastern Mississippi, USA. Little is known about geographic variation in population structure, shape morphology, and sexual size dimorphism (SSD) throughout the drainage. I captured and measured G. flavimaculata from three sites in 2005 and 2006. I analyzed female head width at two of these sites in 2008. Results indicate that body size and population structure vary across a geographic gradient; turtles from the Pascagoula River site were generally larger (both body mass and plastron length) relative to two upstream sites on two tributaries, the Leaf and Chickasawhay rivers. Additionally, body shape in females varied among populations, with Pascagoula River females having a more domed shape than upstream sites where turtles have a more streamlined shape. There was little difference in male shapes among sites. Female-biased SSD typified all three populations with SSD being less pronounced in the two upstream sites. Female head width was significantly different across sites (Pascagoula > Leaf), while there was no difference among sites for male claw length. Presumably, synergistic factors influence population structure, shape morphology, and sexual size dimorphism in Graptemys flavimaculata including: 1) food availability; 2) presence of competitors; 3) thermal environment; 4) presence of alligators; and 5) fluvial conditions.
12 citations
Cites background from "The Ecological Significance of Sexu..."
...Geographic variation of SSD is likely the result of selection for larger female body size for larger clutch size (Ralls 1976; Schoener et al. 1982), competitors (Schoener 1977), or niche partitioning (Schoener 1967, 1968)....
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TL;DR: The ecological overlap of three species of Hawaiian Drosophila: D. mimica D. kambysellisi, and D. imparisetae, has been investigated by analysis of the community matrix, finding considerable ecological diversification among these species and between sexes of the same species.
Abstract: TheDrosophila community of Kipuka Puaulu, Hawaii Volcanoes National Park, was studied by field measurements and laboratory experiments. Phototactic responses were related to oviposition substrates forD. mimica andD. imparisetae, and were shown to reinforce substrate attractiveness. Both species were associated with rottingSapindus fruit, butD. imparisetae, less light tolerant thanD. mimica, was found in deeper shade. Individuals of a third species,D. kambysellisi, were strongly attracted to substratePisonia leaves. The attraction was strong enough to override strong positive phototaxis. The significance of this behavior was related to the adaptive strategy of the species. The sibling species,D. mimica andD. kambysellisi, utilized different substrates and were strongly separated spatially. Differences in substrates and mobility were related to the “grain size” of their environment. Males ofD. kambysellisi andD. imparisetae are located in leking sites above their respective females during the day. This behavior parallels the relatively greater light tolerance of males than of females. The same light response dimorphism inD. mimica is not accompanied by leking behavior, since they mate at night or in greatly subdued light.
11 citations
01 Jan 1978
TL;DR: In this paper, the authors focus on how the peculiar nature of the island environment can affect social behavior and how the environment can mold social systems, producing parallel evolution and thus attesting to the pervasiveness and intensity of the environmental influence.
Abstract: Islands have been called natural biological laboratories—places where one can find numerous experiments in progress at any time. These experiments have rarely been of human design but that is of no matter. We are free to make certain assumptions about the nature of the experiment and then to monitor the results. The results have, in sum, provided us with a fortunate view of the mechanisms of natural selection. It should be noted that we really don’t know much about islands and how they vary from the mainlands and from each other, but we do have a certain working knowledge of certain aspects of their ecology. This information is now beginning to furnish us with a certain insight regarding the influence of environmental factors on behavior, but perhaps the most neglected of these considerations is how the peculiar nature of the island environment can affect social behavior. It is part of the larger question of how the environment can mold social systems, producing parallel evolution and thus attesting to the pervasiveness and intensity of the environmental influence. The goal of this paper is to focus attention on this neglect and to illustrate a few of the ways that the study can begin to proceed. It is first necessary to establish the nature of the island niche.
11 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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