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 hypothesis of convergence in community structure was investigated using taxonomically unrelated lizard communities in Mediterranean climatic areas in central Chile and southern California, and range of resources used as well as utilization functions of individual species were more similar in equivalent sites in the two continents than in nearby Sites in the same continent.
Abstract: Convergence in community structure, under similar long—term climatic conditions, were investigated using taxonomically unrelated lizard communities in Mediterranean climatic areas in central Chile and southern California. The hypothesis of convergence, i.e., physiognomically similar sites in the two continents should have lizard community structures that are more similar to each other than to the structure of lizard communities in nearby areas in the same transect, was tested by comparing the structure of lizard communities in an altitudinal–vegetational transect in each continent. Each transect consisted of a coastal sage, chaparral, and forested montane site. Structure of the lizard communities was characterized by the patterns of habitat, food, and time of activity of the lizard species. For each of these dimensions the total range of resources used by the community as a whole was determined, as well as the utilization pattern of individual species. Utilization patterns of individual species were expressed in a multidimensional vector in which the angle between vectors representing these patterns was used as a measure of ecological similarity between species. The vector method allowed determination of species pairs exhibiting the most similar patterns of resource utilization. The comparison strongly supports the convergence hypothesis. For habitat and time of activity, range of resources used as well as utilization functions of individual species were more similar in equivalent sites in the two continents than in nearby sites in the same continent. Thus, on the average the most similar species (species analogue) is on the equivalent site in the other transect and not in the same continent. Also, in general, the proportions of lizards found, irrespective of species, are the same on analogous resources in the two continents. Habitat species analogues found by comparing sites also similarly partitioned food resources. However, there are some differences in food categories used, since two of the Chilean species eat some vegetation (fruits), but their Californian size—habitat counterparts do not. In addition, the two chaparral sites show very similar mechanisms of generation replacement such that adults go into aestivation by the time hatchings appear. Evidence supporting the hypothesis of a seasonally shrinking food supply as the cause for this pattern is also given.
108 citations
TL;DR: Comparative analyses indicate that population differentiation in male body size is achieved by changes in male size at maturity, without changes in the variance or skewness of male and female size distributions.
Abstract: Female-biased sexual size dimorphism is uncommon among vertebrates and traditionally has been attributed to asymmetric selective pressures favoring large fecund females (the fecundity-advantage hypothesis) and/or small mobile males (the small-male advantage hypothesis). I use a phylogenetically based comparative method to address these hypotheses for the evolution and maintenance of sexual size dimorphism among populations of three closely related lizard species (Phrynosoma douglasi, P. ditmarsi, and P. hernandezi). With independent contrasts I estimate evolutionary correlations among female body size, male body size, and sexual size dimorphism (SSD) to determine whether males have become small, females have become large, or both sexes have diverged concurrently in body size during the evolutionary Xhistory of this group. Population differences in degree of SSD are inversely correlated with average male body size, but are not correlated with average female body size. Thus, variation in SSD among populations has occurred predominantly through changes in male size, suggesting that selective pressures on small males may affect degree of SSD in this group. I explore three possible evolutionary mechanisms by which the mean male body size in a population could evolve: changes in size at maturity, changes in the variance of male body sizes, and changes in skewness of male body size distributions. Comparative analyses indicate that population differentiation in male body size is achieved by changes in male size at maturity, without changes in the variance or skewness of male and female size distributions. This study demonstrates the potential of comparative methods at lower taxonomic levels (among populations and closely related species) for studying microevolutionary processes that underlie population differentiation.
107 citations
Journal Article•
TL;DR: A population of the lizard Anolis carolinensis was studied to determine the variance in breeding success among males as measured by sightings of matings and ability to control areas that overlap females during a prolonged breeding season.
Abstract: Current models of polygynous mating systems predict greater variance in repro- ductive success among males than among females. The sources of variation of breeding success remain poorly known. A population of the lizard Anolis carolinensis was studied to determine the variance in breeding success among males as measured by sightings of matings and ability to control areas that overlap females during a prolonged breeding season. Males seen mating were larger, heavier, and observed more often than males not seen mating. Estimates of the number of females overlapped by individual males also supported the hypothesis that larger males have greater mating success than smaller males. Effects of patterns of receptivity and female choice upon the mating system of A. carolinensis are discussud.
105 citations
Journal Article•
TL;DR: Divergent foraging strategies for terrapins of different head widths may result in habitat partitioning, and food accessibility rather than food abundance may be a limiting factor for Terrapins in areas of high tidal variability.
Abstract: We investigated the foraging ecology of the diamondback terrapin (Malaclemys terrapin) in South Carolina by examining fecal samples for evidence of resource partitioning. From 76-79% of the dietary volume was the salt marsh periwinkle (Littorina irrorata); crabs (Uca pugnax, Sesarma reticulatum, and Callinectes sapidus), barnacles (Balanus), and clams (Polynesoda car- oliniana) constituted the remainder. Dietary partitioning is related to the ontogenetic niche of terrapins. Sexual dimorphism occurs in terrapins with females having larger heads and bodies than males. Terrapins with large head widths ingest significantly larger periwinkles and a wider diversity of prey than terrapins with small head widths. Dietary overlap between males and females is greatest when females are small and decreases as females develop larger enlarged heads. Sexual dimorphism in terrapin trophic structures appears to be partially driven by ecological divergence through resource partitioning. High tides permit terrapins to forage aquatically in upper reaches of the salt marsh. Prey size and distribution are variable and changing tidal heights affect the spatiotemporal availability of prey to foraging terrapins. Divergent foraging strategies for terrapins of different head widths may result in habitat partitioning. Food accessibility rather than food abundance may be a limiting factor for terrapins in areas of high tidal variability. Terrapins are clearly prominent but unrec- ognized macroconsumers in salt marsh ecosystems.
103 citations
TL;DR: The sexes of the Red—eyed Vireo, an abundant insectivorous bird in eastern deciduous woodlands, differed in their foraging heights, with an overlap of only about 35%.
Abstract: The sexes of the Red—eyed Vireo, an abundant insectivorous bird in eastern deciduous woodlands, differed in their foraging heights, with an overlap of only about 35%. The males foraged higher than the females, and non—random sequences of movements were employed to maintain this separation. The foraging level and the nest height of female Red—eyes was similar, whereas the males foraged closer to their singing perches. Thus the foraging efficiency of both sexes was likely greater in accordance with their differing behavior roles. The "small" territory (1.3—1.7 acres) of this species actually consists of a cylinder extending from the forest canopy to the low understory. The associated White—eyed Vireo (Vireo griseus) was generally separated from Red— eyed Vireo by habitat, and the Yellow—throated Vireo (Vireo flavifrons) overlaps in habitat but possesses structural and behavioral differences which indicate different prey preferences. Foraging behavior of migrating Red—eyed Vireos differs markedly from that of breeding birds. Differences were also noted between summer and winter foraging behavior patterns in the White—eyed Vireo. All three vireo species exhibit species—specific patterns of foraging movements. Two other foliage—gleaning insectivorous birds occupying the same forests, the American Redstart (Setophaga ruticilla) and the Acadian Flycatcher (Empidonax virescens), also possess species—specific foraging behaviors (niche—exploitation patterns).
99 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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