Sexual size dimorphism in a natural population of Callicorixa vulnerata (Hemiptera: Corixidae)

2001 ◽  
Vol 133 (3) ◽  
pp. 311-313 ◽  
Author(s):  
P. Nosil
Keyword(s):  
Natural Population ◽  
Body Length ◽  
Sexual Size Dimorphism ◽  
Large Body ◽  
Size Dimorphism ◽  
Fecundity Selection ◽  
Adaptive Processes ◽  
Males And Females ◽  
Spine Number ◽  
Water Boatmen

Sexual size dimorphism occurs in many species. Differences between males and females, in size or other characteristics, may result from sexual selection, fecundity selection, natural selection, non-adaptive processes, or a combination of these pressures (Darwin 1874; Selander 1966; Trivers 1976; Slatkin 1984; Shine 1989). In insects, females with large body size often produce more eggs than smaller females, and femalebiased sexual size dimorphism is commonly attributed to such fecundity selection (e.g., Preziosi and Fairbairn 1997; but see Leather 1988). Water boatmen are detrivorous or zoophagous aquatic insects often inhabiting small ponds of the Northern Hemisphere (Hungerford 1948; Nosil and Reimchen 2001). Female water boatmen are generally larger than males. In this note, I quantify the nature and magnitude of a previously undescribed sexual size dimorphism in a natural population of the water boatman Callicorixa vulnerata Uhler (Hemiptera: Corixidae). I tested for differences between males and females in mean trait size (body length, body weight, mid-leg tarsal length, mid-leg tarsal spine number), and also tested for sexual dimorphism in allometric relationships between tarsal traits and body length.

Proximate mechanisms that contribute to female-biased sexual size dimorphism in an anguid lizard

2004 ◽  
Vol 82 (5) ◽  
pp. 817-822 ◽  
Author(s):  
Pamela L Rutherford
Keyword(s):  
Sexual Size Dimorphism ◽  
Growth Parameters ◽  
Large Body ◽  
Growth Curves ◽  
Differential Mortality ◽  
Differential Growth ◽  
Size Dimorphism ◽  
Proximate Mechanisms ◽  
Males And Females ◽  
Standard Life

Various proximate mechanisms have been proposed to explain sexual size dimorphism (SSD) in vertebrates. Identifying the proximate causation of SSD allows insight into the ultimate reasons why SSD exists. I explored whether differential growth rates and (or) mortality explain SSD in the lizard Elgaria coerulea (Baird and Girard, 1852). I estimated growth parameters for males and females using the logistic-by-weight growth curves and determined survivorship using two complimentary methods: standard life-table calculations and capture–recapture methods. The former calculated age-specific survivorship, whereas the latter tested for differences in survivorship between males and females while considering differences in their recapture rates. I considered age-specific SSD as further evidence of SSD independent of differential mortality. Differences in growth asymptote, not intrinsic growth rate, contribute to SSD in this population. SSD is not due to differential mortality, as there is no difference in survivorship of males and females over 3 years of age. In addition, there is age-specific SSD with females larger than males for individuals 4 years of age and greater. The female-biased SSD may be a result of selection for large body size, although further studies are necessary to identify the ultimate cause of SSD in this species.

scholarly journals Bigger Males, Bigger Females? Pigeons’ Sexual Size Dimorphism

2020 ◽  
pp. 20-24
Author(s):  
P. M. Parés- Casanova ◽  
A. Kabir
Keyword(s):  
Body Weight ◽  
Body Size ◽  
Sexual Size Dimorphism ◽  
Wing Length ◽  
Rensch’S Rule ◽  
Size Dimorphism ◽  
Rensch's Rule ◽  
Neck Thickness ◽  
Males And Females ◽  
Domestic Pigeons

Sexual dimorphism, defined as phenotypic differences between males and females, is a common phenomenon in animals. In this line, Rensch’s rule states that sexual size dimorphism increases with increasing body size when the male is the larger sex and decreases with increasing average body size when the female is the larger sex. Domesticated animals offer excellent opportunities for testing predictions of functional explanations of Rensch’s theory. Pigeon breeds encounters many different functional purposes and selective constraints, which could influence strongly their morphology. The aim of this paper is to examine, for first time, Rensch’s rule among domestic pigeons. It was compiled a database of 12 quantitative traits (body weight, body height, beak thickness, beak length, neck length, neck thickness, wing length, rump width, tail length, tarsus length, tarsus thickness and middle toe length) for males and females of 11 different domestic pigeon breeds: Bangladesh Indigenous, Racing Homer, Turkish Tumbler, Indian Lotan, Kokah, Mookee, Indian Fantail, Bokhara Trumpeter, Bombai, Lahore and Hungarian Giant House; Rock Pigeon (Columba livia) was also considered as wild relative for comparative purposes. Comparative results between males and females showed that only body weight, wing length and neck thickness were consistent with Rensch’s rule. The rest of trait did not present correlations. Among domestic pigeons, there can appear different expressions of dimorphism according to each trait, so it must be considered that Rensch’s rule vary when considering other traits than body weight.

Sexual size dimorphism in the viviparous caecilian amphibian Geotrypetes seraphini seraphini (Gymnophiona: Dermophiidae) including an updated overview of sexual dimorphism in caecilian amphibians

2016 ◽  
Vol 37 (3) ◽  
pp. 291-299 ◽  
Author(s):  
Markus Maerker ◽  
Sandy Reinhard ◽  
Peter Pogoda ◽  
Alexander Kupfer
Keyword(s):  
Sexual Dimorphism ◽  
Body Length ◽  
Sexual Size Dimorphism ◽  
Molecular Ecology ◽  
Female Size ◽  
Sexually Dimorphic ◽  
Size Dimorphism ◽  
Mating System Evolution ◽  
Accurate Comparison ◽  
Widespread Phenomenon

Sexual size dimorphism (SSD) describing intersexual size differences of a given taxon is a widespread phenomenon in the animal kingdom. SSD plays a significant role in understanding life history and mating system evolution. The snakelike morphology of limbless caecilian amphibians lacking obvious secondary sexual characters (in contrast to frogs and salamanders) impedes an accurate comparison between sexes.Here, the phylogenetically derived teresomatan and viviparous caecilianGeotrypetes seraphini seraphiniwas analysed for patterns of sexual dimorphism. In terms of body size females were the larger sex, but when body length was adjusted male-biased intersexual differences in cloacal shape appeared. The larger female size is likely explained by fecundity selection as clutch size was positively correlated to female body length. Unexpectedly a cryptic, ontogeny related variation of the nuchal collars was found. An overview of SSD in caecilians including data for 27 species of nine out of ten existing families revealed a quite high number of taxa showing sexually dimorphic head size dimensions exclusively present among phylogenetically derived teresomatan caecilians. Still further research including insights into the behavioural ecology and molecular ecology of mating systems is warranted to better understand the evolution of sexual size dimorphism of caecilian amphibians.

Size-Dependent Selective Mechanisms on Males and Females and the Evolution of Sexual Size Dimorphism in Frogs

2014 ◽  
Vol 184 (6) ◽  
pp. 727-740 ◽  
Author(s):  
Renato C. Nali ◽  
Kelly R. Zamudio ◽  
Célio F. B. Haddad ◽  
Cynthia P. A. Prado
Keyword(s):  
Sexual Size Dimorphism ◽  
Size Dimorphism ◽  
Size Dependent ◽  
Males And Females

Egg size, prey size, and sexual size dimorphism in digger wasps (Hymenoptera: Sphecidae)

1985 ◽  
Vol 63 (9) ◽  
pp. 2187-2193 ◽  
Author(s):  
Kevin M. O'Neill
Keyword(s):  
Body Size ◽  
Selection Pressure ◽  
Sexual Size Dimorphism ◽  
Species Selection ◽  
Male Size ◽  
Size Dimorphism ◽  
Female Body Size ◽  
Mean Size ◽  
Males And Females ◽  
Apparent Association

Female digger wasps invest substantially in each of their offspring, laying relatively few, large eggs and providing the young with the insect prey on which they depend for food. In a study of six species in the genera Philanthus, Bembecinus, and Bembix, it was found that within each species, there is a positive correlation between female body size and both the size of their ovarial eggs and the size of the prey they provision. In five of the six species, females were larger than males on average. It is suggested that the apparent association between body size and certain aspects of parental investment by females may provide the directional selection pressure that results in the evolution of sexual size dimorphism in digger wasps. In one species, males and females have the same mean size, probably because, in this species, selection pressure on male size is similar to that on females.

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.

Egg-laying site, fecundity and degree of sexual size dimorphism in frogs

2020 ◽  
Vol 131 (3) ◽  
pp. 600-610
Author(s):  
Nelson Rodrigues Silva ◽  
Bianca V M Berneck ◽  
Helio R da Silva ◽  
Célio F B Haddad ◽  
Kelly R Zamudio ◽  
...  
Keyword(s):  
Sexual Size Dimorphism ◽  
Egg Laying ◽  
Female Size ◽  
Selective Force ◽  
Size Dimorphism ◽  
Body Sizes ◽  
Space Limitation ◽  
Males And Females ◽  
Similar Body ◽  
Oviposition Sites

Abstract Female fecundity is an important selective force leading to female-biased sexual size dimorphism (SSD) in frogs. Because anurans exhibit diverse reproductive modes, we investigated whether variation in SSD and fecundity are related with oviposition site. We asked whether arboreal breeding species show pronounced female-biased SSD and if, paradoxically, females have lower fecundity because of the costs of carrying oocytes and amplectant males. Conversely, we tested whether species that deposit eggs in concealed sites show less pronounced SSD, because females do not carry males and space limitation may reduce female size and fecundity. Our results showed that, in general, males were approximately 20% smaller than females. However, for species with hidden oviposition sites, males and females exhibited more similar body sizes and arboreal hylids showed more pronounced female-biased SSD. Overall, fecundity was higher in aquatic breeders, as expected, but in hylids, fecundity was smaller in arboreal breeders, which suggests that arboreality may impose restrictions on fecundity. By analysing SSD in a broader and more specific lineage (Hylidae), we found that reproductive microhabitat may also influence female size and fecundity, playing an important role in the evolution of SSD in frogs at different evolutionary scales.

Geographic variation in size and sexual dimorphism across a hybrid zone between Carrion Crows (Corvus corone corone) and Hooded Crows (C. c. cornix)

1994 ◽  
Vol 72 (9) ◽  
pp. 1543-1550 ◽  
Author(s):  
Nicola Saino ◽  
Fiorenza De Bernardi
Keyword(s):  
Hybrid Zone ◽  
Sexual Size Dimorphism ◽  
Function Analysis ◽  
Absolute Difference ◽  
Ecological Gradient ◽  
Size Dimorphism ◽  
Operational Taxonomic Units ◽  
Corvus Corone ◽  
Males And Females ◽  
Hooded Crows

Sexual size dimorphism was analysed across a hybrid zone existing between allopatric populations of Carrion Crows and Hooded Crows (Corvus corone corone and C. c. cornix) in northwestern Italy. Twenty-five morphological (osteological and plumage) variables were measured in a sample of 1599 specimens obtained from allopatric parental areas and from the hybrid zone. For each morphological variable considered, sexual size dimorphism was measured as the ratio of males/females or the absolute difference between mean sizes of males and females within each subpopulation studied. Overall sexual size dimorphism was described by discriminant function analysis. All the sexual size dimorphism measures adopted showed variation across the hybrid zone according to elevation. Male/female ratios and male–female differences significantly differed between the parental allopatric "operational taxonomic units," Carrion Crows being more dimorphic than Hooded Crows. Across the hybrid zone, sexual size dimorphism was correlated with the phenotypic composition of the crow subpopulations and with size of males but not size of females. The data presented show that sexual size dimorphism is correlated with an ecological gradient and that its geographical variation is determined by variation in size of males only.

Male–male contests for mates, sexual size dimorphism, and sex ratio in a natural population of a solitary parasitoid

2013 ◽  
Vol 100 ◽  
pp. 1-8 ◽  
Author(s):  
Margarete V. Macedo ◽  
Ricardo F. Monteiro ◽  
Mariana P. Silveira ◽  
Peter J. Mayhew
Keyword(s):  
Sex Ratio ◽  
Natural Population ◽  
Sexual Size Dimorphism ◽  
Size Dimorphism ◽  
Solitary Parasitoid ◽  
Male Contests
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