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 intrinsic importance of islands has not inspired the intense research in island biogeography which justifies this review of recent advances, and the realization that oceanic islands are paradigms for geo-graphic entities ranging in size from tiny habitat patches to continents or even the entire earth is realized.
Abstract: Department of Biological Science, Florida State University, Tallahassee, Florida 32306THE BIOLOGICAL IMPORTANCE OF ISLANDSOceanic islands and archipelagoes are intrinsically important to biologists; 5% ofthe land surface of the earth is insular, and if South America, which has been anisland throughout most of its existence, is included the figure rises to 19%. Signifi-cant portions of the evolutionary histories of many economically and biologicallyimportant species occurred on oceanic islands, and if the earth were not liberallysprinkled with isolated bits of land in addition to the "world continent," its biotawould be much poorer.But the intrinsic importance of islands, scientific or economic, has not inspiredthe intense research in island biogeography which justifies this review of recentadvances. Rather it is the realization that oceanic islands are paradigms for geo-graphic entities ranging in size from tiny habitat patches (52, 53) to continents (86,92, 112) or even the entire earth (74). It is almost a platitude that Darwin’s observa-tions in the Galapagos Archipelago and Wallace’s in the Malay Archipelago crystal-lized the then nascent concept of organic evolution by natural selection (13, 110),and many other classical evolutionary advances rest originally on insular observa-tions. Because islands are so clearly isolated from other land masses, island popula-tion data contributed heavily to the realization that most speciation is allopatric(54). Wallace’s Malaysian observations allowed strong inferences about changingsea levels, past land connections, and the position of a line separating two greatbiogeographic provinces (110). Insular isolation is important ecologically becauseit allows us to be virtually certain that an organism encountered on an island is atrue nesiote. Consequently, problems in Community structure and function, such asthe distribution of individuals into species or the trophic relationships among popu-lations, are more readily attacked in an island setting; any organism found there isassuredly a member of the biotic community.161
418 citations
TL;DR: Models are presented which predict an optimal size, defined as that size which takes the least amount of time to satisfy its energy requirements, for several types of predators: I-predators which expend no time or energy in food search alone and which pursue their prey over varying distances; II-predation which expend time and energy while searching for items but none in pursuit; IIa and IIb-predator which expendTime and energy both in search and pursuit.
Abstract: Models are presented which predict an optimal size, defined as that size which takes the least amount of time to satisfy its energy requirements, for several types of predators: I-predators which expend no time or energy in food search alone and which pursue their prey over varying distances; II-predators which expend time and energy while searching for items but none in pursuit; IIa and IIb-predators which expend time and energy both in search and pursuit. All predators are assumed to expend time and energy in handling and swallowing prey. In the simplest models considered, equations are constructed which combine to produce three major properties: (a) larger predators expend more energy in pursuing an item over a given distance than do smaller ones; (b) for most prey items, larger animals expend less time and for somewhat fewer items less energy in handling and swallowing than do smaller predators; (c) time and to a lesser extent energy lost while searching between two items are often not very different ...
403 citations
01 Jan 1972
TL;DR: The history of faunas, whether studied by paleontologists and zoogeographers or by systematists, has customarily been described in terms of phylogeny or colonization—in terms of origin or arrival of species.
Abstract: The history of faunas, whether studied by paleontologists and zoogeographers or by systematists, has customarily been described in terms of phylogeny or colonization—in terms, therefore, of the origin or arrival of species. However, a major element permitting the build-up of faunas has been the coadaptation of their species-the fact that they are ecologically fitted together. Study of this coadaptation among living species is, in fact, a major part of modern ecology. Yet ecologista have, on their part, avoided history; they have avoided any attempt to look closely, theoretically or empirically, at the historical sequence of events in the build-up of a complex coadapted fauna.
398 citations
TL;DR: The crushing phase of biting was modelled and the results show different strategies in allocation of muscle tissue between both sexes, which clearly illustrates that animals of both sexes can bite much harder than required for most insect food items, which does not support the niche divergence hypothesis.
Abstract: 1. Two often cited hypotheses explaining sexual head size dimorphism in lizards are: sexual selection acting on structures important in intrasexual competition, and reduction of intersexual competition through food niche separation.
2. In this study some implicit assumptions of the latter hypothesis were tested, namely that an increase in gape distance and bite force should accompany the observed increase in head size. These assumptions are tested by recording bite forces, in vivo, for lizards of the species Gallotia galloti. In this species, male lizards have significantly larger heads than female conspecifics of similar snout–vent length.
3. Additionally, the average force needed to crush several potential prey species was determined experimentally and compared with the bite force data. This comparison clearly illustrates that animals of both sexes can bite much harder than required for most insect food items, which does not support the niche divergence hypothesis. The apparent ‘excess’ bite force in both sexes might be related to the partially herbivorous diet of the animals.
4. To unravel the origin of differences between sexes in bite capacity, the crushing phase of biting was modelled. The results of this model show different strategies in allocation of muscle tissue between both sexes. The origin of this difference is discussed and a possible evolutionary pathway of the development of the sexual dimorphism in the species is provided.
393 citations
TL;DR: Under conditions of reduced interspecific competition, there is selective pressure for age groups to diverge in resource use, and the evolution and significance of the "age structure component" of niche width is discussed.
Abstract: Many species pass through several distinct age classes (instars or year classes) as they grow. The variety of resources used by age classes effectively expands niche width. This "age-specific component" of niche width is analyzed for a desert scorpion, Paruroctonus mesaensis, whose populations exhibit both instars and discrete year classes. Another purpose of this paper is to evaluate if instars or year classes function as "ecological species" by showing the same differences in morphology and resource use as exists between biological species. The similarity of the growth ratio (Dyar's constant) to Hutchinson's Santa Rosalia ratio has promoted the speculation that the size divergence between age groups has the same ecological basis as that between competing species. Empirical differences between species for a variety of resource-related parameters were determined from a survey of the literature. These interspecific differences are compared to differences between age classes of the same population. Intraspe...
376 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.
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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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