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
More filters
TL;DR: The reproductive and fat body cycles and some life-history traits of the viviparous skink Mabuya frenata were studied in a seasonal habitat in the state of Sao Paulo, southeastern Brazil.
Abstract: The reproductive and fat body cycles and some life-history traits of the viviparous skink Mabuya frenata were studied in a seasonal habitat in the state of Sao Paulo, southeastern Brazil. Reproductive activity is markedly cyclical in both sexes. Females reach sexual maturity at juvenile body sizes, have an extended gestation period lasting 9-12 months, and give birth to 2-8 young (mean 4.9 ? 1.1), mainly during August through October. Fat stored in fat bodies during the wet season is used up during gestation in females and during increased spermatogenic activity in males. Females reach a larger adult body size than males, but males have relatively larger heads. The reproductive and life-history traits observed for M. frenata are similar to those of other South American Mabuya.
55 citations
TL;DR: The data are suggestive of microevolutionary adjustment of morphology in the Florida populations over the last 50 years, but a competing hypothesis that invokes multiple undetected introductions is not excluded.
Abstract: from 25 Florida localities reveals that 10 of the 12 scale characters analyzed are geographically variable. Although Florida lizards are known to be descended from Cuban and Bahamian stocks, a simple Cuba-Bahama dichotomy is not apparent in the Florida material. Discrete phena cannot be recognized on morphological grounds, perhaps due to random genetic processes operating in small founding populations. Secondary sexual dimorphism is characteristic of Florida lizards and is itself geographically variable. Sexual dimorphism is most strongly and consistently expressed in numbers of dorsals, ventrals, gulars and subdigital lamellae, for all of which males characteristically exceed females. Comparisons of samples collected early in the colonization of Florida at or near points of initial establishment, with samples collected at the same localities in 1981 reveal significant differences in numbers of subdigital lamellae and dorsal scales for certain samples. Intralocality variation in scale characters has not changed measurably over what it was 20 to 50 years ago. Recent samples are slightly less morphologically distinct from one another than are early samples, and covariation among scale characters appears to have increased slightly over time. The data are suggestive of microevolutionary adjustment of morphology in the Florida populations over the last 50 years, but a competing hypothesis that invokes multiple undetected introductions is not excluded.
54 citations
TL;DR: It is concluded that isopterans are the main item in the diet of C. littoralis in Restinga da Barra de Maricá, both for juveniles and adults, and the lack of seasonal, sexual, or ontogenetic variation in its diet results from the massive consumption of these insects.
Abstract: We investigated the feeding habits of the teiid lizard Cnemidophorus littoralis in the markedly seasonal habitat of Restinga da Barra de Marica (22o57'S, 43o50'W), Rio de Janeiro State, Brazil, to evaluate to what extent its diet is ontogenetically, sexually, and/or seasonally conservative. Lizard stomach contents were analyzed, identified, counted, estimated for volume (in mm3), and grouped in four classes (active, sedentary, and clumped preys, and plant material). The relative contribution of each food class to the total prey volume consumed by adult males and females and juveniles was compared in three ways: between juveniles and adults, sexes, and seasons (wet and dry). Sexual dimorphism in head size was tested by comparing head width and jaw length using analysis of covariance (ANCOVA). Isopterans were the most important prey item, occurring in 93% of the lizard stomachs examined and corresponding to 96.4% of total prey content and 69.7% of total prey volume. They occurred in high frequencies in the stomachs of C. littoralis throughout all study months. We found no sexual, ontogenetic, or seasonal differences in C. littoralis diet although the sexes differed significantly in head width. We concluded that isopterans are the main item in the diet of C. littoralis in Restinga da Barra de Marica, both for juveniles and adults. The lack of seasonal, sexual, or ontogenetic variation in its diet results from the massive consumption of these insects. Isopterans are small, occur in clumps, and are available year-round, and thus are an advantageous food item for the active forager C. littoralis. We also found sexual dimorphism in the head size of C. littoralis: males have wider heads than females. This dimorphism, however, does not seem to be related with the diet of the species, and is probably a result of sexual selection.
53 citations
Cites background or methods from "The Ecological Significance of Sexu..."
...Although several studies have related sexual dimorphism in head size with sexual differences in diet composition (e.g., Schoener, 1967, 1968; Schoener & Gorman, 1968; Preest, 1994), the larger heads of male C. littoralis at Barra de Maricá are probably more related to sexual selection since males…...
[...]
...Many lizard species show a relationship between the size and/or volume of prey items and mouth part sizes (e.g., Schoener, 1967, 1968; Schoener & Gorman, 1968; Vitt, 1983; Preest, 1994)....
[...]
...The volume in mm3 of each individual prey was estimated by multiplying its three dimensions (Schoener, 1967)....
[...]
...Also, because in many lizard species the sexes differ in size, sexual differences in mouth part sizes may result in sexual differences in diet (e.g., Schoener, 1967)....
[...]
TL;DR: Aggressive encounters were staged between two species of Puerto Rican lizards which share the same microhabitat (syntopic) and it seems that A. cooki and A. cristatellus recognize each other as competitors; it is improbable that this interspecific aggression was caused by the two species misidentifying each otherAs conspecifics.
Abstract: Aggressive encounters were staged between two species of Puerto Rican lizards (Anolis cooki and Anolis cristatellus) which share the same microhabitat (syntopic). The intensity of these interspecific matches was as great as their respective conspecific matches. When the two species interacted with either “look alike” congeners (A. cooki with A. monensis and A. cristatellus with A. gundlachi) or with the quite different appearing A. evermanni, aggressive intensity was only 1/6 that of the cooki-cristatellus encounters. It seems that A. cooki and A. cristatellus recognize each other as competitors; it was improbable that this interspecific aggression was caused by the two species misidentifying each other as conspecifics. Because A. cristatellus eventually dominated A. cooki during staged encounters, it is predicted A. cristatellus should ecologically displace A. cooki in their syntopic zones of contact.
52 citations
28 Apr 1968
52 citations
References
More filters
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)....
[...]
...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)....
[...]