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Journal ArticleDOI

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
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Journal ArticleDOI
TL;DR: The morphological differences observed are probably not caused by exploitative competition between the species, but rather appear attributable to the modification of the relative influence of sexual and natural selection on both sexes.
Abstract: Podarcis bocagei and P. carbonelli are two closely related lacertid species, very similar morphologi- cally and ecologically. We investigated sexual dimor- phism patterns presented by both species in allopatry and in sympatry. Sexual size and shape dimorphism pat- terns were analyzed using both multivariate and geo- metric morphometric techniques. Multivariate morpho- metrics revealed a marked sexual dimorphism in both species—males being larger with more robust habitus and females presenting a longer trunk. General patterns of sexual size dimorphism are not modified in sympatry, although there is evidence for some morphological change in male head size. The application of geometric morphometrics offered a more detailed image of head shape and revealed that males present a more developed tympanic area than do females, while females have a more rounded head. Differences in the degree of sexual shape dimorphism were detected in sympatry, but no consistent patterns were observed. From the results of the study, and based on previous knowledge on the pop- ulations studied, we conclude that the morphological dif- ferences observed are probably not caused by exploita- tive competition between the species, but rather appear attributable to the modification of the relative influence of sexual and natural selection on both sexes. J. Mor- phol. 268:152-165, 2007 2007 Wiley-Liss, Inc.

135 citations


Cites background from "The Ecological Significance of Sexu..."

  • ...This, combined with the minute differences in diet between sympatric and allopatric populations, excludes the hypothesis of character displacement and, hence, exploitative competition as a cause for the shifts observed in SD patterns in both species (Schoener, 1967, 1977; Watkins, 1996)....

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Journal ArticleDOI
TL;DR: Whereas evolutionary changes in display duration appear to be linked to sexual size dimorphism, measures of display complexity were more tightly associated with the need to facilitate species recognition and the type of light environment in which the display is typically performed.

132 citations


Cites background from "The Ecological Significance of Sexu..."

  • ...However, in at least some anoles, the origin of SSD may also reflect natural selection driving the sexes into different ecological niches to minimize intersexual competition for resources (e.g. Schoener 1967, 1968)....

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Journal ArticleDOI
TL;DR: In a population of adders (Vipera berus) in Southwest Sweden, melanistic males were heavier than normal coloured males of the same length and Victory in male-male sexual combats was positively related to size.
Abstract: In a population of adders (Vipera berus) in Southwest Sweden, melanistic males were heavier than normal coloured males of the same length. Victory in male-male sexual combats was positively related to size. Higher risk of predation in the black morph was inferred from experiments showing a high predator attack rate on models of the black morph. Even the bright colour in newly moulted basking males of the normal morph gives cryptic protection. In females, melanism probably also affects body size and risk of predation by visually searching predators. The thermoregulatory influence of black colour, the reproductive success and the maintenance of two colour morphs in the population are discussed.

130 citations

Journal ArticleDOI
TL;DR: Digestive tracts of wild guppies, Poecilia reticulata (Pisces: Poeciliidae), contained mainly benthic algae and aquatic insect larvae, but growth rates were slower than those of fish raised on Daphnia or commercial dried food.
Abstract: Digestive tracts of wild guppies, Poecilia reticulata (Pisces: Poeciliidae), contained mainly benthic algae and aquatic insect larvae. In the laboratory, guppies matured on diets consisting solely ...

128 citations

Journal ArticleDOI
TL;DR: In this paper, the authors present a set of sozialen Variationen with dem einzigartigen Lebensraum and den geographischen Besonderheiten der Insel in Zusammenhang zu stehen, in which the bestehen are the Schwierigkeiten der Verteidigung reduziert and die Ernahrung sowie die Moglichkeit der mannlichen Partnerbewachachung besser.
Abstract: Resume Dans la population equine de l‘ile de Shacklesford Banks au large de la cote est est USA, des changements majeurs de l'organisation sociale sont apparus. Au lieu de vivre classiquement en harems occupant des territoires se “chevauchant”, on s'est rendu compte que certains harems defendaient leur territoire et meme que certains chevaux n'appartenaient meme pas a des groupes fixes. L'existence de ces variations sociales semble etre due a l'habitat et aux caracteristiques geographiques uniques de l’ile. Les territoires, dont les limites couraient le long de l‘ile, n'existaient que la ou celle-ci est etroite, la visibilite non obstruee et ou les principales zones de vegetation courent le long de l'axe principal de l’ile. Ce n'est qu‘a ces endroits que les difficultes de defense etaient reduites et les posibilites de se nourrir et d'assurer la garde pour les mâles etaient superieures. Dans les zones de hautes dunes de sable et de foret epaisse, des assemblages provisoires ont ete observes et des harems sans territoire fixe occupaient les zones semi-ouvertes accidentees avec des mâles celibataires. Une fois les territoires defendus, de nombreux aspects des relations sociales individuelles changent. Les etalons a territoire ont moins tendance a influencer les activites quotidiennes de leurs groupes et plus a s'occuper de leurs femelles dominantes et a regrouper leurs femelles subordonnees que les etalons sans territoire. De plus, les distances individuelles sont generalement plus grandes entre animaux vivant dans des harems territoriaux par opposition a des harems non territoriaux. Zusammenfassung Bei einer Pferdepopulation auf Shacklesford Banks, einer Insel vor der amerikanischen Ostkuste, haben sich grosere soziale Organisationsveranderungen ereignet. Anstatt in den typischen Harems in sich uberschneidenden Heimatgebieten zu leben, wurde festgestellt, das einige Harems ihre Territorien verteidigten und einige Pferde noch nicht einmal in festen Gruppen lebten. Das Bestehen dieser sozialen Variationen schien mit dem einzigartigen Lebensraum und den geographischen Besonderheiten der Insel in Zusammenhang zu stehen. Territorien, deren Grenzen uber die ganze Breite der Insel verliefen, gab es nur an den Stellen, wo die Insel schmal und die Sicht unbegrenzt war und wo die Vegetationszonen entlang der Langsachse der Insel verliefen. Nur hier waren die Schwierigkeiten der Verteidigung reduziert und die Ernahrung sowie die Moglichkeit der mannlichen Partnerbewachung besser. Wo die Sanddunen hoch und die Walder dicht waren, fanden zeitweise Zusammenschlusse statt, und nichtterritoriale Harems bewohnten zusammen mit den weibchenlosen Mannchen die uneinheitliche, halboffene Landschaft. Mit dem Beginn der Territoriumsverteidigung veranderten sich auch zahlreiche Aspekte der individuellen sozialen Verhaltnisse. Territoriale Hengste neigten weniger dazu, das tagliche Aktivitatsmuster ihrer Gruppe zu beeinflussen, und tendierten eher dazu, ihre dominanten Weibchen zu versorgen und zu pflegen und ihre untergeordneten Weibchen zusammenzutreiben als ihre nicht-territorialen Gegenstucke. Bei territorialen Harems wurden auch grosere Abstande zwischen den einzelnen Tieren beobachtet als bei nichtterritorialen. Summary In a horse population on Shackleford Banks, an island off the American east coast, major changes in social organisation have occurred. Instead of typically living in harems occupying overlapping home ranges, it was found that some harems defended territories and some horses did not even live in fixed membership groups. The existence of these social variations appeared to be correlated with the unique habitat and geographical features of the island. Territories, whose boundaries ran the width of the island, only occurred where the island was narrow, the visibility unrestricted and the essential vegetation zones ran along the island's long axis. Only here were the difficulties in defending reduced and feeding and male mate-guarding opportunities increased. Where the sand dunes were high and forest dense temporary assemblages occurred and non-territorial harems occupied the patchy semi-open area with the batchelor males. Once territories were defended many aspects of individual social relationships became altered. Territorial stallions were less likely to influence the daily activity patterns of their groups and more likely to groom their dominant females and round-up their subordinate females than were their non-territorial counterparts. In addition, interpersonal distances were likely to be greater among horses living in territorial, as opposed to nonterritorial, harems.

128 citations

References
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Journal ArticleDOI

292 citations

Journal ArticleDOI
01 Oct 1964-Ecology
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

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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