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: Three arboreal desert lizards (Urosaurus graciosus, U. ornatus, and Sceloporus ma- gister: Iguanidae) occur in close association in riparian habitats of central Arizona and data suggest that all species exploit the temporally abundant insects.
Abstract: Three arboreal desert lizards (Urosaurus graciosus, U. ornatus, and Sceloporus ma- gister: Iguanidae) occur in close association in riparian habitats of central Arizona. The lizards were studied over 2 yr, to determine patterns of resource utilization. Urosaurus graciosus and U. ornatus are similar in body size, but Sceloporus magister is much larger. Juvenile S. magister are, however, similar in body size to adults of both Urosaurus. Ratios of head and body size (larger species:smaller species) reveal similarities between the Urosaurus species and between both species of Urosaurus and juvenile S. magister, but large differences be- tween Urosaurus species and adult S. magister. Active body temperatures of all three species were similar, and the only significant difference in time of activity was between S. magister and U. ornatus. The habitat of U. graciosus reached higher air and substrate temperatures than that of U. ornatus and received greater incident radiation (S. magister occurred in both habitats). Urosaurus ornatus and S. magister avoid extremes of temperatures by entering crevices in trees, retreating under loose bark, or entering mammal burrows or nests, whereas U. graciosus retreat to shaded portions of tree trunks and are thus less able to avoid extremes. Urosaurus graciosus occur in relatively small trees and forage in the canopy; U. ornatus inhabit large trees and forage on trunks and large limbs; S. magister occupy trees of all sizes but forage primarily on trunks and large limbs, and on the ground. Prey sizes were significantly different among species and with one exception (S. magister), signifi- cantly different within species among years. Diets of all three change seasonally and yearly, presum- ably in association with resource availability. Diet overlaps are often high but fluctuate seasonally and yearly. Data on resource availability suggest that all species exploit the temporally abundant insects. Data presented on habitat utilization, activity times, body temperatures, and food eaten reveal partitioning of the arboreal habitat in three dimensions between U. graciosus and U. ornatus and partitioning of prey size between the two Urosaurus as a group, and S. magister.
68 citations
TL;DR: The results suggest that whereas in males, sexual selection seems to be operating on bite performance, in the case of females, natural selection seem to be the most likely and most important selective pressure driving the variation in head size.
Abstract: 461..475 Although differential selective pressures on males and females of the same species may result in sex-specific evolutionary trajectories, comparative studies of adaptive radiations have largely neglected within-species varia- tion. In this study, we explore the potential effects of natural selection, sexual selection, or a combination of both, on bite performance in males and females of 19 species of Liolaemus lizards. More specifically, we study the evolution of bite performance, and compare evolutionary relationships between the variation in head morphology, bite performance, ecological variation and sexual dimorphism between males and females. Our results suggest that in male Liolaemus, the variation in bite force is at least partly explained by the variation in the degree of sexual dimorphism in head width (i.e. our estimate of the intensity of sexual selection), and neither bite force nor the morphological variables were correlated with diet (i.e. our proxy for natural selection). On the contrary, in females, the variation in bite force and head size can, to a certain extent, be explained by variation in diet. These results suggest that whereas in males, sexual selection seems to be operating on bite performance, in the case of females, natural selection seems to be the most likely and most important selective pressure driving the variation in head size. © 2010 The Linnean Society of London, Biological Journal of the Linnean Society, 2010, 101, 461-475. ADDITIONAL KEYWORDS: diet - ecomorphology - interspecific variation - natural selection - sexual differences - sexual selection.
67 citations
Cites background from "The Ecological Significance of Sexu..."
...However, competition for scarce resources (e.g. food) may also lead to niche divergence between the sexes, and associated phenotypic divergence through the process of natural selection (cf. Selander, 1966; Schoener, 1967)....
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TL;DR: A population of the northern fence lizard was studied for four years along a riverine pine bluff in northern Mississippi for comparison with previous studies and to identify factors influencing mortality rates and annual variations in reproduction, growth, survival, and population densities.
Abstract: A population of the northern fence lizard Sceloporus undulatus was studied for four years along a riverine pine bluff in northern Mississippi for comparison with previous studies and to identify factors influencing mortality rates and annual variations in reproduction, growth, survival, and population densities. Reproductive parameters were similar to those of other eastern woodland populations, with clutch size averaging 9.4. Most males and females were reproductive by age one year. Age ratios were 1:1 between yearlings and older adults; sex ratios favored females more in older age groups and resulted from higher mortality rates in males. Annual survivorship averaged 30% for yearlings and adults and showed a loose inverse correlation with injury rates (broken tails) on different vegetational zones of the study area. Spring population densities were among the highest reported for this species, at up to 72 (717 g)/ha. Tree trunks (mostly pines) were perch sites >70% of the time. Females used larger diameter oak trees more than did males, possibly reducing injury rates and enhancing survivorship. Growth, volume of food in stomachs, reproduction, and survival seemed little affected by variations in precipitation between two years; rather, population fluctuations seemed most critically tied to survival from egg to hatchling. Two life tables were most similar to one for an Ohio population in survival to first breeding (5-12%), cohort generation time (1.8 yr), and age two contributing most to the net reproductive rate.
66 citations
TL;DR: It is suggested that large female size is likely a plesiomorphic character of gekkonids and that large head size in males results from sexual selection theory.
Abstract: We describe the ecology of the gecko Gymnodactylus geckoides amarali in the Cerrado of central Brazil and using published data, compare it with the conspecific Gymnodactylus geckoides geckoides from the Caatinga of northeastern Brazil. Gymnodactylus geckoides amarali is rupicolous, living primarily in rock crevices in “campos rupestres” (rocky fields), which are highly patchy in Cerrado. Field body temperatures were low and associated with environmental temperatures, suggesting thermoconformity. Termites were the most important food item, and consumption was greatest during the dry season. We suggest that access to termites is facilitated by the shallow soils used by G. g. amarali and by its well-developed chemosensory apparatus. Reproduction was concentrated in the dry season, a pattern known for very few Cerrado squamates, possibly because of the higher availability of termites during that period. Clutch size was significantly correlated with female size, a pattern unknown in any other gecko, a...
66 citations
TL;DR: Le dimorphisme sexuel dans la taille de la tete est due a une inhibition precoce de la croissance de the tete par les androgenes testiculaires.
Abstract: Le dimorphisme sexuel dans la taille de la tete est due a une inhibition precoce de la croissance de la tete par les androgenes testiculaires.
65 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
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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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