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572 záznamů v Medvik

Kniha

Physical attractiveness and the theory of sexual selection : results from five populations

Ann Arbor : Museum of Anthropology, University of Michigan, 1996

Anthropological papers ; No. 90

XIV, 174 s. : il. ; 18 cm

Článek

Resource availability, mating opportunity and sexual selection intensity influence the expression of male alternative reproductive tactics

For example, variation in resources and sexual selection intensity is expected to influence the pay-off ...

Journal of evolutionary biology. 2018 ; 31 (7) : 1035-1046. [pub] 20180519

J Evol Biol
ISSN 1420-9101
Medvik
Zdroj

The expression of alternative reproductive tactics can be plastic and occur simultaneously depending on cues that vary spatially or temporally. For example, variation in resources and sexual selection intensity is expected to influence the pay-off of each tactic and shape the decision of which tactic to employ. Males of the nuptial gift-giving spider Pisaura mirabilis can adopt three tactics: offering a genuine prey gift, a 'worthless' non-nutritious gift or no gift. We hypothesized that resources and/or male body condition, and mating opportunity and sexual selection intensity, vary over the course of the mating season to shape the co-existence of alternative traits. We measured these variables in the field over two seasons, to investigate the predictions that as the mating season progresses, (i) males become more likely to employ a gift-giving tactic, and (ii) the likelihood of switching from worthless to genuine gifts increases. Prey availability increased over the season and co-varied with the propensity of males to employ the gift-giving tactic, but we found no support for condition-dependent gift giving. Males responded to an increase in female availability by increasing their mating effort (gift production). Furthermore, the frequency of genuine gift use increased with sexual selection intensity, consistent with the assumption that sperm competition intensity increases with time. Our results suggest that the frequency of alternative tactics is shaped by seasonal changes in ecological factors and sexual selection. This leads to relaxed selection for the gift-giving tactic early in the season when females are less choosy and resources more scarce, and increased selection for genuine gifts later in the season driven by mating opportunity and risk of sperm competition.

Článek

Sexual selection and the biology of beauty

Lidé města. 2004 ; 6 (2) : s. 18-45.

ISSN 1212-8112
Medvik
Zdroj

Článek

Sexuální orientace a selektivita vnímání (experimentální studie)
[Sexual orientation and selectivity of perception]

Československá psychiatrie. 1993 ; Roč. 89 (č. 6) : s. 358-362.

ISSN 0069-2336
Medvik
Zdroj

Článek

Sex differences in parental care: Gametic investment, sexual selection, and social environment

investment by males and females that precipitates into sex difference in care, (2) different intensity of sexual ...

Evolution. 2015 ; 69 (11) : 2862-75. [pub] 20151013

ISSN 1558-5646
Medvik
Zdroj

Male and female parents often provide different type and amount of care to their offspring. Three major drivers have been proposed to explain parental sex roles: (1) differential gametic investment by males and females that precipitates into sex difference in care, (2) different intensity of sexual selection acting on males and females, and (3) biased social environment that facilitates the more common sex to provide more care. Here, we provide the most comprehensive assessment of these hypotheses using detailed parental care data from 792 bird species covering 126 families. We found no evidence for the gametic investment hypothesis: neither gamete sizes nor gamete production by males relative to females was related to sex difference in parental care. However, sexual selection correlated with parental sex roles, because the male share in care relative to female decreased with both extra-pair paternity and frequency of male polygamy. Parental sex roles were also related to social environment, because male parental care increased with male-biased adult sex ratios (ASRs). Taken together, our results are consistent with recent theories suggesting that gametic investment is not tied to parental sex roles, and highlight the importance of both sexual selection and ASR in influencing parental sex roles.

Článek

Phenotypic differentiation is associated with divergent sexual selection among closely related barn swallow populations

Sexual selection plays a key role in the diversification of numerous animal clades and may accelerate ...

Journal of evolutionary biology. 2016 ; 29 (12) : 2410-2421. [pub] 20160904

J Evol Biol
ISSN 1420-9101
Medvik
Zdroj

Sexual selection plays a key role in the diversification of numerous animal clades and may accelerate trait divergence during speciation. However, much of our understanding of this process comes from phylogenetic comparative studies, which rely on surrogate measures such as dimorphism that may not represent selection in wild populations. In this study, we assess sexual selection pressures for multiple male visual signals across four barn swallow (Hirundo rustica) populations. Our sample encompassed 2400 linear km and two described subspecies: European H. r. rustica (in the Czech Republic and Romania) and eastern Mediterranean H. r. transitiva (in Israel), as well as a potential area of contact (in Turkey). We demonstrate significant phenotypic differentiation in four sexual signalling axes, despite very low-level genomic divergence and no comparable divergence in an ecological trait. Moreover, the direction of phenotypic divergence is consistent with differences in sexual selection pressures among subspecies. Thus, H. r. transitiva, which have the darkest ventral plumage of any population, experience directional selection for darker plumage. Similarly, H. r. rustica, which have the longest tail feathers of any population, experience directional selection for elongated tail feathers and disruptive selection for ventral plumage saturation. These results suggest that sexual selection is the primary driver of phenotypic differentiation in this species. Our findings add to growing evidence of phenotypic divergence with gene flow. However, to our knowledge, this is the first study to relate direct measures of the strength and targets of sexual selection to phenotypic divergence among closely related wild populations.

Článek

Antidepresiva v léčbě sexuálních dysfunkcí u mužů
[Antidepressants in the treatment of male sexual dysfunction]

The author describes studies of therapeutic efficaccy of antidepressants in the treatment of male sexual ...

Žourková, Alexandra, 1953-
Autor Autorita

Interní medicína pro praxi. 2005 ; 7 (9) : 405-407.

Interní med. praxi (Print)
ISSN 1212-7299
Medvik
Zdroj

Autorka podává přehled prací, které sledovaly efekt vybraných antidepresiv v léčbě sexuálních dysfunkcí u mužů. Antidepresiva stimulující sexuální aktivitu (moklobemid, trazodon, bupropion) se osvědčila při léčbě poruch libida a erektilní dysfunkce, serotoninergní antidepresiva patří k lékům volby předčasné ejakulace.

The author describes studies of therapeutic efficaccy of antidepressants in the treatment of male sexual dysfunction. Antidepressants stimulating sexual activity (moclobemide, bupropion, trazodone) demonstrate good results in the therapy of decreased libido and erectile dysfunction, serotonergic antidepressants are used in the treatment of premature ejaculation.