Selective pressures, variability, and sexual dimorphism in stalk-eyed flies (diopsidae)

1985 ◽  
Vol 72 (4) ◽  
pp. 204-206 ◽  
Author(s):  
D. Burkhardt ◽  
I. de la Motte
Keyword(s):  
Sexual Dimorphism ◽  
Selective Pressures

scholarly journals Sexual dimorphism in skeletal shape in voles (Arvicolinae): disparate selection on male bodies and female heads

2020 ◽  
Vol 101 (4) ◽  
pp. 951-957
Author(s):  
Jeremy S Morris ◽  
Nala Rogers ◽  
Alan R Rogers ◽  
David R Carrier
Keyword(s):  
Sexual Dimorphism ◽  
Food Processing ◽  
Processing Efficiency ◽  
Selective Pressures ◽  
Skeletal Size ◽  
Quality Diet ◽  
Males And Females ◽  
Selection For ◽  
Functional Indices ◽  
Caloric Requirements

Abstract Sexual dimorphism evolves as a response to different selective pressures on males and females. In mammals, sexual selection on traits that improve a male’s ability to compete for access to mates is a common cause of sexual dimorphism. In addition to body mass, adaptations in specific components of the musculoskeletal system that increase strength, stability, and agility, may improve male fighting performance. Here we test the hypotheses that males, when compared to females, are more specialized for physical competition in their skeletal anatomy and that the degree of this sexual dimorphism increases with the intensity of male–male competition. In three species of voles (Cricetidae: Arvicolinae: Microtus), we found partial support for these hypotheses. Male-biased sexual dimorphism in a set of functional indices associated with improved fighting performance was identified in the postcranial anatomy. This dimorphism was greatest in the polygynous Microtus californicus, absent in the monogamous M. ochrogaster, and intermediate in the promiscuous or socially flexible M. oeconomus. However, in the skull, we found results opposite to our predictions. Females had larger skulls relative to overall skeletal size than did males. This may be associated with selection for increased food processing efficiency, which should be highly important because of the compounding effects of increased caloric requirements during gestation and lactation, and the generally low-quality diet of voles. In addition, larger heads in females may be associated with selection for greater digging ability or for defending offspring. These results suggest disparate selective pressures on the postcranial skeletons and skulls of male and female voles.

scholarly journals Seasonal dynamics of dental sexual dimorphism in the Atlantic stingray Dasyatis sabina

1996 ◽  
Vol 199 (10) ◽  
pp. 2297-2306 ◽  
Author(s):  
S Kajiura ◽  
T Tricas
Keyword(s):  
Sexual Dimorphism ◽  
Fossil Record ◽  
Reproductive Season ◽  
Sexually Dimorphic ◽  
Mating Season ◽  
Selective Pressures ◽  
Dasyatis Sabina ◽  
Atlantic Stingray ◽  
Cartilaginous Fishes

Cartilaginous fishes continuously replace their teeth throughout their life (polyphyodonty) and often show a sexually dimorphic dentition that was previously thought to be an invariant sex character. Radial vector analysis of tooth shape in the polyphyodontic stingray Dasyatis sabina across a consecutive 24 month period shows a stable molariform morphology for females but a periodic shift in male dentition from a female-like molariform to a recurved cuspidate form during the reproductive season. The grip tenacity of the male dentition is greater for the cuspidate form that occurs during the mating season than for the molariform dentition that occurs during the non-mating season. Dental sexual dimorphism and its sex-dependent temporal plasticity probably evolved via polyphyodontic preadaptation under selective pressures on both sexes for increased feeding efficiency and sexual selection in males to maximize mating success. These phenomena are important considerations for the identification and classification of cartilaginous fishes and possibly other polyphyodontic vertebrates in the fossil record.

scholarly journals Evolution of Drosophila buzzatii wings: Modular genetic organization, sex-biased integrative selection and intralocus sexual conflict

2021 ◽  
Author(s):  
Patricia Paola Iglesias ◽  
Fabio Andrade Machado ◽  
S Llanes ◽  
E Hasson ◽  
E M Soto
Keyword(s):  
Sexual Dimorphism ◽  
Common Garden ◽  
Wing Shape ◽  
Population Divergence ◽  
Isofemale Line ◽  
Main Function ◽  
Intralocus Sexual Conflict ◽  
Selective Pressures ◽  
Drosophila Buzzatii ◽  
Line Design

The Drosophila wing is a structure shared by males and females with the main function of flight. However, in males, wings are also used to produce songs, or visual displays during courtship. Thus, observed changes in wing phenotype depend on the interaction between sex-specific selective pressures and the genetic and ontogenetic restrictions imposed by a common genetic architecture. Here, we investigate these issues by studying how the wing has evolved in twelve populations of Drosophila buzzatii raised in common-garden conditions and using an isofemale line design. The between-population divergence shows that sexual dimorphism is greater when sex evolves in different directions. Multivariate Qst-Fst analyses confirm that male wing shape is the target for multiple selective pressures, leading males' wings to diverge more than females' wings. While the wing blade and the wing base appear to be valid modules at the genetic (G matrix) and among-population (D matrix) levels, the reconstruction of between-population adaptive landscapes (Ω matrix) shows selection as an integrative force. Also, cross-sex covariances reduced the predicted response to selection in the direction of the extant sexual dimorphism, suggesting that selection had to be intensified in order to circumvent the limitations imposed by G. However, such intensity of selection was not able to break the modularity pattern of the wing. The results obtained here show that the evolution of D. buzzatii wing shape is the product of a complex interplay between ontogenetic constraints and conflicting sexual and natural selections.

Growth and Sexual Dimorphism in the Dibbler, Parantechinus apicalis (Marsupialia, Dasyuridae)

1999 ◽  
Vol 21 (2) ◽  
pp. 239
Author(s):  
H. Mills ◽  
Z. German R ◽  
C. Lambert ◽  
P. Bradley M
Keyword(s):  
Sexual Dimorphism ◽  
Mating Systems ◽  
Growth Patterns ◽  
Sexually Dimorphic ◽  
Breeding Strategies ◽  
Wild Animals ◽  
Selective Pressures ◽  
Morphological Studies ◽  
In Captivity ◽  
Males And Females

Sexual dimorphism in animals has been recognised as being associated with particular breeding strategies or mating systems since Darwin's Origin of Species. Frequently, in polygamous situations, females express a variety of attributes to attract males, and males compete with each other for access to females. This produces different selective pressures in each sex, which in tum produces differing morphologies (Leigh 1995). Thus, the emphasis of morphological studies of sexual differences tends to focus on adults and not the growth patterns that generate those differences. Growth patterns in marsupials have been shown to be variable between species (Gemmell and Hendrikz 1993). Previous studies of dasyurid species in captivity concluded that the onset of dimorphism occurs prior to or during weaning (Whitford, Fanning and White 1982; Williams and Williams 1982), but wild animals are not sexually dimorphic until after weaning (Soderquist 1995). These studies have generally examined the growth rates of males and females and the timing of the onset of sexual dimorphism, but little attention has been focussed on how the differences between the sexes are generated.

scholarly journals Evidence of Wing Shape Sexual Dimorphism in Aedes (Stegomyia) albopictus in Mallorca, Spain

2021 ◽  
Vol 9 ◽  
Author(s):  
Júlia López-Mercadal ◽  
André Barretto Bruno Wilke ◽  
Carlos Barceló ◽  
Miguel Angel Miranda
Keyword(s):  
Sexual Dimorphism ◽  
Mosquito Control ◽  
Oviposition Behavior ◽  
Blood Feeding ◽  
Wing Shape ◽  
Adult Mosquito ◽  
Evolutionary Diversification ◽  
Selective Pressures ◽  
Host Seeking ◽  
Males And Females

The Asian tiger mosquito Aedes albopictus (Skuse, 1894) is a highly invasive species widely distributed on the Spanish Mediterranean coast and the Balearic archipelago. Most studies involving this species in Spain have been focused on surveillance and control methods. However, micro-evolutionary studies for Ae. albopictus in Spain have been traditionally neglected. Morphological diversity could be the result of long-term evolutionary diversification in responses to selective pressures such as temperature, precipitation, food availability, predation, or competition that may influence flight activity, host-seeking, and blood-feeding behavior. Wing geometric morphometric have been used not only to study micro- and macro-evolution in mosquitoes but also in studies of population structuring and sexual dimorphism. Therefore, the main goal of this study was to investigate the wing shape patterns of Ae. albopictus populations to unveil sexual dimorphism that could provide information about their ecology and behavior. Mosquito eggs were collected using oviposition traps at the main campus of the University of the Balearic Islands (Palma de Mallorca, Spain) and reared under laboratory conditions. In order to study wing shape variation patterns in Ae. albopictus males and females, the left wing of each adult mosquito was removed and analyzed based on 18 landmarks. Our results indicated strong levels of sexual dimorphism between Ae. albopictus males and females. Furthermore, according to the cross-validated reclassification test, males were correctly distinguished from females with an accuracy of 84% and females from males 75%. We observed a significant sexual dimorphism in the wing shape patterns of Ae. albopictus when considering different seasonal patterns (spring vs. autumn). Our results suggested that selective pressures may affect males differently to females. Host-seeking, blood-feeding, and oviposition behavior of females may act as a major driver for wing shape sexual dimorphism. These results should be considered for the development of more effective and targeted mosquito control strategies.

scholarly journals Sex-Biased Parent-Offspring Conflict

Behaviour ◽  
1992 ◽  
Vol 123 (3-4) ◽  
pp. 261-289 ◽  
Author(s):  
Tomas Redondo ◽  
Montserrat Gomendio ◽  
Rosario Medina
Keyword(s):  
Sexual Dimorphism ◽  
Empirical Evidence ◽  
Parental Investment ◽  
Conflict Theory ◽  
Domestic Sheep ◽  
Evolution Of Sex ◽  
Selective Pressures ◽  
Parental Expenditure ◽  
Sex Biases

AbstractIn species showing sexual dimorphism, parents may obtain different fitness returns per unit of parental expenditure from sons and daughters. Under these circumstances, parents are expected to invest extra resources in offspring of the most profitable sex. However, it is unclear whether sex-biased expenditure is the result of selection acting on parents, their offspring, or both. Current parent-offspring conflict theory is used to investigate whether sex biases in parental expenditure should be accompanied by sex biases in parent-offspring conflict. It is suggested that, in general, greater conflict should be expected between parents and offspring of the favoured sex. Specifically, greater conflict is predicted among mother-son dyads than among mother-daughter dyads in most polygynous birds and mammals. Data on domestic sheep, as well as empirical evidence available for other species (mainly ungulates), lends support to the prediction. The prediction is further extended to cercopithecine primates, a group which lacks clear sex-biases in parental investment. In this case, differences in fitness returns per unit of parental expenditure between the daughters of dominant and subordinate mothers are positively related to differences in the extent of mother-daughter conflict. The results from this study highlight the important role that selective pressures acting on the offspring phenotype may have played in the evolution of sex-biased patterns of parental investment.

Sexual dimorphism in an under-ice spawning fish: the burbot (Lota lota)

2013 ◽  
Vol 91 (10) ◽  
pp. 732-740 ◽  
Author(s):  
P.A. Cott ◽  
T.A. Johnston ◽  
J.M. Gunn
Keyword(s):  
Sexual Dimorphism ◽  
Visual Cues ◽  
Liver Lipid ◽  
Sexually Dimorphic ◽  
Lipid Concentration ◽  
Lota Lota ◽  
Selective Pressures ◽  
Liver Lipid Concentration ◽  
Boreal Fishes ◽  
Bladder Mass

Sexual dimorphic characteristics arise in response to differing selective pressures on the sexes and can be used to attract mates or signal reproductive readiness. How sexual dimorphism is expressed where visual cues may be of limited use is an underexplored aspect of reproductive ecology. The burbot (Lota lota (L., 1758)) is a common boreal fish that is not overtly sexually dimorphic. It spawns mid-winter in a light-limited under-ice environment. We examined a variety of morphological and reproductive characteristics in burbot from a northern lake over one full year to assess both seasonal and sex-based variation. Spawning occurred under ice in early February. Seasonal variation was more pronounced in females for many of the traits examined. Growth, fin lengths, swim bladder mass, and liver lipid concentration did not differ between the sexes. Male burbot had significantly higher body condition, larger gas glands, and smaller livers. Males also had significantly larger gonads than females, unusual for boreal fishes. The high gonadal investment of male burbot suggests that sperm competition may be intense in this species. This study demonstrates that sexual dimorphism can be subtle and is present in a seemingly monomorphic species—the burbot.

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