Search results for "Sexual selection"

Intersexual competition among humans: prosocial towards the opposite sex and proself towards the same sex?

2017

In a research conducted on a sample of participants from three countries (N = 256): Poland, Ukraine and Denmark, a hypothesis of the moderating impact of other person sex on the level of social value orientation of men and women was tested. The study applied the now rarely used method of measuring social value orientation: the Warsaw Method, which was expected to reveal more subtle differences between men and women than those observed in the studies using the most popular social value orientation measurement tools, such as decomposed games. The direction of the observed relationship proved to be compatible with the predictions resulting from the phenomenon of intrasexual competition for a p…

Testis asymmetry in birds: the influences of sexual and natural selection

2014

Gonad size and shape asymmetries are particularly common in birds. Although some obvious size and shape differences between the left and right testes in birds were first documented more than a century ago, little is known about what influences the variation across species in either the degree or the direction of these asymmetries. Here we show that a left bias in size is the most likely ancestral state in most orders and families, and that there is a weak but significant negative relation between the degree of size and shape asymmetries. In extant species, testis size and shape symmetries increase with the degree of sperm competition (relative testes mass), but those relations are significa…

Extra-pair paternity and male characteristics in the pied flycatcher

1995

The pied flycatcher (Ficedula hypoleuca) is sexually dichromatic with extreme variation in male plumage coloration. The benefit for males of having black plumage is controversial, and few studies have found evidence for a sexual selection benefit of being black rather than brown. However, blacker males may be better able to achieve extra-pair fertilizations (EPFs), which may be an important component of sexual selection. We studied the role of EPFs in sexual selection in the pied flycatcher by establishing a set-up where two males with different back coloration (blacker vs browner) bred simultaneously near each other. DNA fingerprinting analysis revealed that 11% of offspring resulted from …

The stability of genetic variance?covariance matrix in the presence of selection

2007

Quantitative genetics provides one of the most important frameworks in which evolutionary biology and evolution can be studied. The primary goals of this field of study include the attempts to understand the history of selection that has resulted in the multiple phenotypic traits we observe today, and to predict the future trajectory of the multiple traits. Within quantitative genetics it is the genetic variance–covariance matrix G which summarizes the additive genetic variation of multiple traits and the genetic covariances between the traits, together with selection that control the direction and rate of evolution. The product of these two elements determine the response to selection from…

Maintenance of genetic variation in sexual ornamentation : role of precopulatory and postcopulatory sexual selection

2010

Sexual selection on male body size and assortative pairing in Gammarus pulex (Crustacea: Amphipoda): field surveys and laboratory experiments

2004

Variation in size-assortative pairing was studied in relation to sexual selection on male body size in the amphipod Gammarus pulex, using both transverse and longitudinal surveys of natural populations. In addition, the influence of male–male competition on size-assortative pairing was tested in the laboratory. In both surveys, the intensity of sexual selection was positive and significant for male body size but not for females, and size-assortative pairing was positive and significant. The magnitude of size-assortative pairing, however, varied significantly between populations. The magnitude of size-assortative pairing was positively correlated with the intensity of sexual selection on mal…

KAMA: A Temperature-Driven Model of Mate Choice Using Dynamic Partner Representations

2008

KAMA is a model of mate-choice based on a gradual, stochastic process of building up representations of potential partners through encounters and dating, ultimately leading to marriage. Individuals must attempt to find a suitable mate in a limited amount of time with only partial knowledge of the individuals in the pool of potential candidates. Individuals have multiple-valued character profiles, which describe a number of their characteristics (physical beauty, potential earning power, etc.), as well as preference profiles, that specify their degree of preference for those characteristics in members of the opposite sex. A process of encounters and dating allows individuals to gradually bui…

Mating strategies and resulting patterns in mate guarding crustaceans : an empirical and theoretical approach

2012

Because of strong costs associated with each mating event, females are usually not as available for reproduction as males at any given time. Males are therefore in competition with each other for access to receptive females, hence leading to strong sexual selection. One textbook case of such a mating system occurs in moulting crustaceans where females can only be fertilized during a short period following their moult. This has favoured the evolution male strategies to monopolize females before their period of receptivity. Such a precopulatory mate guarding is widespread among many taxa and represents one of the most striking example of males’ competitive traits favoured by sexual selection.…

SEQUENCE EVOLUTION OF THE SPERM LIGAND ZONADHESIN CORRELATES NEGATIVELY WITH BODY WEIGHT DIMORPHISM IN PRIMATES

2007

Sexual selection has repeatedly been shown to be the probable driving force behind the positive Darwinian evolution of genes affecting male reproductive success. Here we compare the sequence evolution of the sperm ligand zonadhesin with body mass dimorphism in primates. In contrast to previous related studies, the present approach takes into account not only catarrhine primates, but also platyrrhines and lemurs. In detail, we analyze the sequence evolution of concatenated zonadhesin fragments (555 bp) of four Lemuroidea, five Platyrrhini, and seven Catarrhini, using the rate ratio of nonsynonymous to synonymous substitutions (dn/ds=omega). Unexpectedly, subsequent regression analyzes betwee…

Male reproductive senescence as a potential source of sexual conflict in a beetle

2011

The link between senescence and reproductive success is a contentious yet crucial issue to our understanding of mate choice, sexual conflict, and the evolution of ageing. By imposing direct (i.e., male fertility) or indirect (i.e., zygote viability) reproductive costs to females, male senescence may lead to sexual conflict at different levels. For example, ageing may affect male ability to deliver sperm, thus setting the scene for sexual conflict over mating, and/or may affect the quality of individual sperm cells, generating the potential for sexual conflict over fertilizing strategies. We addressed these issues by studying the mating behavior, reproductive fitness, and fertilization patte…