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: Results within G. galloti suggest natural selection is not the sole source of phenotypic diversity across environments, but rather that variation in the strength of, or response to, sexual selection may play an important role in generating morphological diversity in environmentally diverse settings.
Abstract: Identifying the factors generating ecomorphological diversity within species can provide a window into the nascent stages of ecological radiation. Sexual dimorphism is an obvious axis of intraspecific morphological diversity that could affect how environmental variation leads to ecological divergence among populations. In this paper we test for sex-specific responses in how environmental variation generates phenotypic diversity within species, using the generalist lizard Gallotia galloti on Tenerife (Canary Islands). We evaluate two hypotheses: the first proposes that different environments have different phenotypic optima, leading to shifts in the positions of populations in morphospace between environments; the second posits that the strength of trait-filtering differs between environments, predicting changes in the volume of morphospace occupied by populations in different environments. We found that intraspecific morphological diversity, provided it is adaptive, arises from both shifts in populations’ position in morphospace and differences in the strength of environmental filtering among environments, especially at high elevations. However, effects were found only in males; morphological diversity of females responded little to environmental variation. These results within G. galloti suggest natural selection is not the sole source of phenotypic diversity across environments, but rather that variation in the strength of, or response to, sexual selection may play an important role in generating morphological diversity in environmentally diverse settings. More generally, disparities in trait–environment relationships among males and females also suggest that ignoring sex differences in studies of trait dispersion and clustering may produce misleading inferences.
5 citations
06 Sep 2018
TL;DR: Comparisons of morphometry and relative frequencies of sexes and both male colour morphs of the Striped Lava Lizard among three distinct populations from the State of Rio Grande do Norte, Brazil suggest that populations are under distinct selection pressures.
Abstract: Sexual dimorphism, including dichromatism, is a strong indicative of past or ongoing processes of sexual selection, which can also promote discrete variants within a sex. These variants can be either in terms of morphology, colouration, physiology, and behaviour, such as colour morphs with alternative mating tactics. However, as sexual selection acts in a populational level, distinct populations might be under different selection pressures conferring distinct levels of dimorphism and distinct number, and frequencies, of morphs in the cases in which it occurs. The Striped Lava Lizard, Tropidurus semitaeniatus , is a small (≤14g) flat lizard inhabitant of rocky outcrops distributed throughout all the semi-arid Caatinga biome in Brazil. Two discrete colour morphs were described within adult males from a single population, but their function, presence, frequencies, and morphological differences are still unexplored, especially among populations. Here, with a sample of 343 individuals, we present comparative data of morphometry and relative frequencies of sexes and both male colour morphs of T. semitaeniatus among three distinct populations from the State of Rio Grande do Norte, Brazil. Relative frequencies of male morphs differed substantially among populations. Male morphs are dimorphic in body size only within the population with equal relative morph frequencies, while the remaining populations have opposite morph-biased frequencies. Our results suggest that populations are under distinct selection pressures, which should be explored in future behavioural studies addressing intra and intersexual interactions between male morphs.
5 citations
Cites background from "The Ecological Significance of Sexu..."
...There are many different hypotheses to explain it, including mechanisms that relate sexual dimorphism to gamete investment or anisogamy (Wells, 2007), resource partitioning or availability (Schoener, 1967), sexual selection (Olsson et al....
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...…hypotheses to explain it, including mechanisms that relate sexual dimorphism to gamete investment or anisogamy (Wells, 2007), resource partitioning or availability (Schoener, 1967), sexual selection (Olsson et al., 2002), species’ life history (Andersson, 1994), and phylogeny (Isaac, 2005)....
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10 Apr 2008
TL;DR: Most differences among the populations were the significant differences in the size of prey consumed, and in the morphological characters associated to feeding.
Abstract: Widely distributed snakes exposed to different conditions of temperature and precipitation throughout their distributions may present geographic variation in the kinds, classes and/or sizes of the preys consumed. Such interpopulacional differences in diet frequently result in modifications of morphological characters associated to feeding. In this study, I investigate whether Bothrops jararaca populations from coastal and adjacent mid-elevation sites of the Serra do Mar and plateau in Sao Paulo state presented differences in diet, feeding frequency between the seasons of the year, and in morphological characters associated to feeding. I analyzed 831 specimens among immature and adults of both sexes deposited in the Colecao Herpetologica do Instituto Butantan (IBSP). Data concerning 42 fed individuals from the studied areas taken from unpublished works were also included. Additional aspects of B. jararaca feeding biology such as the consumption of multiple prey items and ontogenetic shift in diet were also discussed. Juveniles from the mid-elevation sites feed on endothermic preys (mammals) in higher frequency in relation to that from the coastal sites, which might be due to the higher anuran availability throughout the year at the coastal sites, and/or because the juveniles from the mid-elevation sites select and they are capable of ingest endothermic preys despite their small body size. There were no significant differences among sub-adults and adults from the two populations in the kinds (ectothermic and endothermic) and classes (taxonomic groups) of the prey consumed, which is possibly related to the fact that the individuals from both sites consumes endothermic prey as soon as possible throughout the ontogeny and abandon relatively small items. Although the jararacas from the mid-elevation sites probably are less active during the coldest and driest months of the year and feed less frequently during this period in relation to that of the coastal sites, these individuals did not seem to compensate the fewer opportunities of taking prey by feeding in higher frequency in relation to the coespecifics from the 18 coastal sites during the hottest and warmest months of the year. Most differences among the populations were the significant differences in the size of prey consumed, and in the morphological characters associated to feeding. The specimens from mid-elevation populations consume relatively larger prey and they have larger bodies, relative larger heads, and are stouter for most of the size classes established. It is possible that the more seasonal climate of the mid-elevation sites restricts the extension of the activity period and the feeding efficiency of snakes, which could correspond to a selective agent related to the consumption of larger prey. The difference in diet might be one of the factors that are related to differences in body dimensions between populations from the coast and from mid-elevation sites. It is suggested that some morphological differences should be related to the species phenotypic plasticity and other to evolutionary changes. VARIACAO GEOGRAFICA EM CARACTERES MORFOLOGICOS E NA DIETA EM POPULACOES DE BOTHROPS JARARACA (SERPENTES: VIPERIDAE) NO ESTADO
5 citations
Cites background from "The Ecological Significance of Sexu..."
...…e/ou diferencial dos recursos alimentares entre os sexos e a conseqüente maximização no sucesso de forrageamento intrasexual ou a possível redução da competição intraespecífica (e.g. SCHOENER, 1967; SHINE, 1986; 1989; 1991; HOUSTON & SHINE, 1993; SHETTY & SHINE, 2002; VINCENT et al., 2004)....
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01 Jan 2015
TL;DR: There was no sexual dimorphism for morphological characters of H. agrius, except for body width, with females having wider bodies than males, what might be related to fecundity, and the most important consumed prey was orthopterans.
Abstract: Hemidactylus agrius is a rare gecko from semi-arid formations of northeastern Brazil. We provide herein relevant information on the natural history of this Neotropical gecko species, regarding microhabitat use, sexual dimorphism and feeding habits of a population from a typical semi-arid Caatinga area. The majority of H. agrius were found inactive beneath barks of trees during daylight, evidencing that this kind of microhabitat seem suitable retreat sites. There was no sexual dimorphism for morphological characters of H. agrius, except for body width, with females having wider bodies than males, what might be related to fecundity. The most important consumed prey was orthopterans, and the trophic niche overlap between sexes did not differ from expected by chance. The dietary composition of males and females seems explained neither by differences in head shape nor of dissimilar microhabitat use. Our findings expanded the knowledge on the poorly known H. agrius, thereby contributing to understand the natural history of Hemidactylus lizards with small geographical range.
4 citations
TL;DR: Investigation of a population of Acanthodactylus blanfordi Boulenger from Hormozgan Province, southern Iran showed that sexual dimorphism is significant in some metric and pholidosis characters, and can be explained by intrasexual selection as well as by the fecundity advantage hypothesis.
Abstract: Detailed investigations carried out on a population of Acanthodactylus blanfordi Boulenger, 1918, from Hormozgan Province, southern Iran, to clarify the presence of sexual dimorphism and determine clear-cut characters for distinguishing the two sexes showed that sexual dimorphism is significant (P<0.05) in some metric and pholidosis characters. Males have relatively longer snout-vent length and tail length than females. The results can be explained by intrasexual selection as well as by the fecundity advantage hypothesis. Differences in colour pattern and colouration between the two sexes are not obvious.
4 citations
Cites background from "The Ecological Significance of Sexu..."
...…of ecological niches between the two sexes as a strategy to minimize competition, possibly for food resources, has been considered as a factor for the presence of sexual dimorphism in size and body shape in some lizard taxa (SCHOENER 1976) and it should be the likely case in A. blanfordi as well....
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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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