scholarly journals Size- and sex-specific predation on dung flies by amphibian and arthropod predators – size match matters

2019 ◽  
Author(s):  
Wolf U. Blanckenhorn ◽  
Gabriele Cozzi ◽  
Gregory Jäggli ◽  
Juan Pablo Busso
Keyword(s):  
Body Size ◽  
Sexual Size Dimorphism ◽  
Rana Temporaria ◽  
Large Body ◽  
Mechanistic Study ◽  
Mating Activity ◽  
Size Dimorphism ◽  
Arthropod Predators ◽  
Body Sizes ◽  
Predation Rates

Because predator-prey interactions in nature are multifarious, linking phenomenological predation rates to the underlying behavioural or ecological mechanisms is challenging. Size- and sex-specific predation has been implicated as a major selective force keeping animals small, affecting the evolution of body size and sexual size dimorphism. We experimentally assessed predation by various amphibian (frogs and toads) and arthropod predators (bugs, flies, spiders) on three species of dung flies with similar ecology but contrasting body sizes, sexual size dimorphism and coloration. Predators were offered a size range of flies in single- or mixed-sex groups. As expected based on optimal foraging theory, some anurans (e.g. Bufo bufo) selected larger prey, thus selecting against large body size of the flies, while others (Bombina variagata and Rana esculenta) showed no such pattern. Small juvenile Rana temporaria metamorphs, in contrast, preferred small flies, as did all arthropod predators, a pattern that can be explained by larger prey being better at escaping. The more mobile males were not eaten more frequently or faster than the cryptic females, even when conspicuously colored. Predation rates on flies in mixed groups permitting mating activity were not higher, contrary to expectation, nor was predation generally sex-specific. We conclude that the size-selectivity of predators, and hence the viability selection pattern exerted on their prey, depends foremost on the relative body sizes of the two in a continuous fashion. Sex-specific predation by single predators appears to contribute little to sexual dimorphism. Therefore, the mechanistic study of predation requires integration of both the predator’s and the prey’s perspectives, and phenomenological field studies of predation remain indispensable.

scholarly journals Experimental size- and sex-specific predation on dung flies by amphibian and arthropod predators

2021 ◽  
pp. 1-10
Author(s):  
Wolf U. Blanckenhorn ◽  
Gabriele Cozzi ◽  
Gregory Jäggli ◽  
Juan Pablo Busso
Keyword(s):  
Sexual Size Dimorphism ◽  
Rana Temporaria ◽  
Optimal Foraging Theory ◽  
Bufo Bufo ◽  
Mechanistic Study ◽  
Mating Activity ◽  
Size Dimorphism ◽  
Arthropod Predators ◽  
Body Sizes ◽  
Predation Rates

Abstract Because predator-prey interactions in nature are multifarious, linking phenomenological predation rates to underlying behavioral or ecological mechanisms is challenging. Size- and sex-specific predation has been implicated as a major selective force keeping animals small, directing the evolution of body size and sexual size dimorphism. We experimentally assessed predation by 4 amphibian and 3 arthropod species (bug, fly, spider) on 3 species of dung flies with similar ecology but contrasting body sizes, sexual size dimorphism, and coloration. Predators were offered a size range of male and/or female individuals of one prey species. As expected based on optimal foraging theory, some anurans (Bufo bufo) preferred larger prey individuals, others (Bombina variagata, Rana esculenta) showed no preference. Small juvenile Rana temporaria metamorphs preferred small prey, as did all arthropod predators, a pattern that may be explained by gape limitation or larger prey escaping better. Presumably more mobile males were not preyed upon more frequently or faster than cryptic females, even when conspicuously colored. Contrary to expectation, predation rates on flies in mixed groups facilitating mating activity were not higher, nor was predation generally sex-specific, hence contributing little to sexual dimorphism. We conclude that the size-selectivity of predators, and hence the viability selection pattern exerted on their prey, depends foremost on the relative body sizes of the two in a continuous fashion, in addition to any specific prey defense mechanisms. Therefore, the mechanistic study of predation requires integration of both the predator and prey perspectives, and phenomenological field studies of predation remain indispensable.

Growth, maturity, and sexual dimorphism in the wood turtle, Clemmys insculpta

1990 ◽  
Vol 68 (4) ◽  
pp. 672-677 ◽  
Author(s):  
Jeffrey E. Lovich ◽  
Carl H. Ernst ◽  
John F. McBreen
Keyword(s):  
Body Size ◽  
Sexual Dimorphism ◽  
Carapace Length ◽  
Sexual Size Dimorphism ◽  
Von Bertalanffy ◽  
Size Dimorphism ◽  
Adult Females ◽  
Body Sizes ◽  
Von Bertalanffy Growth Model ◽  
Wood Turtle

Growth in the wood turtle (Clemmys insculpta) is described using the von Bertalanffy growth model and nonlinear regression. Growth in both sexes is similar until about 160 mm plastron length. Males grew at a faster rate after this size. Males appear to mature at a larger size and later age than females, although age-specific body size is highly variable. Sexual size dimorphism, in carapace length, is pronounced, with males attaining mean body sizes significantly larger (1.07–1.10 times) than those of adult females. Plastron length is an inappropriate measure of sexual size dimorphism because of the development of plastral concavity in males. Females tend to predominate in samples, possibly owing to differential maturity of the sexes. The direction of sexual size dimorphism may be maintained by intrasexual competition among males for access to females. Data for several adults captured at intervals of from 9 to 20 years support the concept of indeterminate growth.

Pythons in the pergola: the ecology of 'nuisance' carpet pythons (Morelia spilota) from suburban habitats in south-eastern Queensland

2001 ◽  
Vol 28 (6) ◽  
pp. 573 ◽  
Author(s):  
S. Fearn ◽  
B. Robinson ◽  
J. Sambono ◽  
R. Shine
Keyword(s):  
Body Size ◽  
Food Habits ◽  
Sexual Size Dimorphism ◽  
Activity Patterns ◽  
Dietary Composition ◽  
Seasonal Activity ◽  
Size Dimorphism ◽  
South Eastern ◽  
Two Cities ◽  
Body Sizes

Carpet pythons (Morelia spilota) are large (to >4 m, 11 kg) non-venomous snakes that are widely distributed across mainland Australia. In many parts of their range, viable populations persist even in highly disturbed urban and suburban habitats. Over a six-year period, we collected 258 ‘nuisance’ pythons from two cities (Brisbane and Ipswich) in south-eastern Queensland. Most of these snakes were reported by members of the general public, often after the snakes had consumed domestic pets or cage-birds. We provide data on seasonal activity patterns, body sizes, sexual size dimorphism, reproduction and food habits of these snakes. Snakes were active and fed year-round, primarily on domestic and commensal birds and mammals. Dietary composition shifted with body size: one small snake consumed a lizard, intermediate-sized snakes took mostly mice, rats and parrots, and large snakes fed on larger items such as cats, brushtail possums and poultry. Adult male pythons engaged in combat bouts during the breeding season, and (perhaps as an adaptation to enhance success in such bouts) grew larger and were more heavy-bodied than conspecific females.

Pattern of sexual size dimorphism supports the inverse of Rensch’s rule in two frog species

2014 ◽  
Vol 64 (1) ◽  
pp. 87-95 ◽  
Author(s):  
Di Lu ◽  
Cai Quan Zhou ◽  
Lian Jun Zhao ◽  
Wen Bo Liao
Keyword(s):  
Body Size ◽  
Sexual Size Dimorphism ◽  
Rana Temporaria ◽  
Rensch’S Rule ◽  
Size Dimorphism ◽  
Rensch's Rule ◽  
Frog Species ◽  
Mean Size ◽  
The Common ◽  
Males And Females

Rensch’s rule describes that sexual size dimorphism (SSD) increases with body size (hyperallometry) when males are larger, and decreases with body size (hypoallometry) when males are smaller. In this paper, on the basis of mean adult body size resulting from 18 populations of the common frogRana temporariaand 24 populations of the Tibetan frogNanorana parkeri, we tested the consistency of allometric relationships between males and females with Rensch’s rule. Our results show that the variation in degree of female-biased SSD increased with increasing mean size at intraspecific levels in two species, which is consistent with the inverse of Rensch’s rule. Furthermore, we tested the hypothesis that the degree of SSD decreased with increasing altitudes. Inconsistent with the predications of our hypothesis, we found no relationships between the degree of SSD and altitude for the two species investigated. These findings suggest that females living in adverse climates in high altitudes cannot adjust their body size as plastically as males.

Potential mechanisms of phenotypic divergence in body size between Newfoundland and mainland black bear populations

2001 ◽  
Vol 79 (9) ◽  
pp. 1650-1660 ◽  
Author(s):  
Shane P Mahoney ◽  
John A Virgl ◽  
Kim Mawhinney
Keyword(s):  
Sexual Selection ◽  
Body Size ◽  
Body Mass ◽  
Sexual Size Dimorphism ◽  
Large Body ◽  
Black Bear ◽  
Relative Difference ◽  
Black Bears ◽  
Male Body ◽  
Size Dimorphism

Phenotypic variation in body size and degree of sexual size dimorphism of North American black bears (Ursus americanus) was quantified for populations from New Brunswick, Quebec, Ontario, Maine, Alaska, and the island of Newfoundland. Based on a model of island biogeography developed by Case, we predicted that body size should be larger in Newfoundland bears than in mainland populations. The presence of few large predators and minimal competition between herbivore prey on Newfoundland allow an appropriate test of the model (i.e., food availability for bears may differ between populations on the mainland and in Newfoundland). In addition, sexual-selection theory predicts that the coevolution of polygyny and large size will be coupled with an increase in sexual size dimorphism. Therefore, we also predicted that among the six populations, male body mass should scale hyperallometrically with female body mass (i.e., slope > 1). Analysis of deterministic growth curves indicated that bears from Newfoundland attained greater asymptotic body size than populations on the mainland, which supports our first prediction. On average, the relative difference in asymptotic body mass between females from the island and mainland populations was 55%, while the relative difference between males was 37%. However, we found that sexual size dimorphism did not increase disproportionately with body mass among the six populations, which refuted our second prediction. We discuss a range of abiotic and biotic selection pressures possibly responsible for larger body size in Newfoundland bears. We suggest that the ability to exploit seasonally abundant and spatially dispersed dietary protein by female and male black bears on the island has been and is still a primary environmental factor selecting for large body size in Newfoundland bears. Although the relationship between sexual size dimorphism and body size is tenuous (slope [Formula: see text] 1), it does suggest that (an)other adaptive mechanism(s), opposing sexual selection for extreme male size, explain(s) a large amount of the variation in sexual size dimorphism among black bear populations.

scholarly journals A uni- and multivariate analysis approach to reveal sexual size dimorphism in Iranian populations of Hypera postica (Coleoptera: Curculionidae)

Biologia ◽  
2015 ◽  
Vol 70 (9) ◽  
pp. 1228-1233 ◽  
Author(s):  
Ehsan Sanaei ◽  
Marjan Seiedy ◽  
Farzaneh Momtazi
Keyword(s):  
Body Size ◽  
Sexual Size Dimorphism ◽  
Egg Laying ◽  
Morphological Divergence ◽  
High Fecundity ◽  
Hypera Postica ◽  
Size Dimorphism ◽  
Female Body Size ◽  
Divergence Pattern ◽  
Iranian Populations

Abstract Body size dimorphism between genders is a commonly observed phenomenon in insects, usually manifested in larger female body size. Sexual Size Dimorphism (SSD) varies from species to species, the degree and direction influenced by certain evolutionary pressures. Intraspecific variation in SSD may also occur between populations. The Hypera postica (Gyllenhal, 1813) is a well-known alfalfa plant pest that shows a degree of morphological divergence in its populations. The female alfalfa weevils are very fecund and have a larger body size compared to males. To improve our knowledge on magnitude and direction of SSD in alfalfa weevil, we studied 200 specimens of H. postica from four Iranian populations (Karaj1, Karaj2, Tuyserkan and Jovein). 10 morphological variables from three external anatomic parts (pronotum, elytra and rostrum) and 45 ratio characters were statistically analyzed in order to determine the amount of SSD in Iranian populations. In addition we investigated for morphological divergence pattern in mentioned populations. The results of this study show that a low degree of morphological divergence occurs in Iranian populations. Measured variables indicate that the SSD pattern of H. postica is compatible with the Rensch’s rule, and is related to high fecundity of females and a lack of strong sexual selection. Also it is mentioned that the larger rostrum in females may correspond to its unique role in egg laying.

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