Search results for "Sexual selection"
showing 10 items of 255 documents
The Bruce effect revisited: is pregnancy termination in female rodents an adaptation to ensure breeding success after male turnover in low densities?
2017
Pregnancy termination after encountering a strange male, the Bruce effect, is regarded as a counterstrategy of female mammals towards anticipated infanticide. While confirmed in caged rodent pairs, no verification for the Bruce effect existed from experimental field populations of small rodents. We suggest that the effect may be adaptive for breeding rodent females only under specific conditions related to populations with cyclically fluctuating densities. We investigated the occurrence of delay in birth date after experimental turnover of the breeding male under different population composition in bank voles (Myodes glareolus) in large outdoor enclosures: one-male–multiple-females (n = 6 p…
Paternal age negatively affects sperm production of the progeny.
2021
International audience; Parental age has profound consequences for offspring’s phenotype. However, whether patrilineal age affects offspring sperm production remains unknown, despite the importance of sperm production for male reproductive success in species facing post-copulatory sexual selection. Using a longitudinal dataset on ejaculate attributes of the houbara bustard, we showed that offspring sired by old fathers had different age-dependent trajectories of sperm production compared to offspring sired by young fathers. Specifically, they produced less sperm (−48%) in their first year of life, and 14% less during their lifetime. Paternal age had the strongest effect, with weak evidence …
Evolution of yolk androgens in birds: development, coloniality and sexual dichromatism
2007
18 pages; International audience; Current theory recognizes the adaptive value of maternal effects in shaping offspring phenotypes in response to selective pressures and vindicates the value of these traits in fostering adaptation and speciation. Yolk androgens in birds are a relatively well-known maternal effect and have been linked to adaptations related to development, coloniality life, and sexual selection. We tested whether interspecific patterns of yolk androgen levels (androstenedione and testosterone) were related to interspecific variation in development, sexual selection, and coloniality. First, we found no relationship between androgen levels and duration of development as reflec…
Post-copulatory sexual selection allows females to alleviate the fitness costs incurred when mating with senescing males.
2019
8 pages; International audience; Male senescence has detrimental effects on reproductive success and offspring fitness. When females mate with multiple males during the same reproductive bout, post-copulatory sexual selection that operates either through sperm competition or cryptic female choice might allow females to skew fertilization success towards young males and as such limit the fitness costs incurred when eggs are fertilized by senescing males. Here, we experimentally tested this hypothesis. We artificially inseminated female North African houbara bustards with sperm from dyads of males of different (young and old) or similar ages (either young or old). Then, we assessed whether si…
Postcopulatory sexual selection generates speciation phenotypes in Drosophila.
2013
Background: Identifying traits that reproductively isolate species and the selective forces underlying their divergence is a central goal of evolutionary biology and speciation research. There is growing recognition that postcopulatory sexual selection which can drive rapid diversification of interacting ejaculate and female reproductive tract traits that mediate sperm competition may be an engine of speciation. Conspecific sperm precedence (CSP) is a taxonomically widespread form of reproductive isolation but the selective causes and divergent traits responsible for CSP are poorly understood. Results: To test the hypothesis that postcopulatory sexual selection can generate reproductive iso…
Elevated oxidative stress in pied flycatcher nestlings of eumelanic foster fathers under low rearing temperatures
2019
Striking variation in melanin coloration within natural populations is likely due to the different fitness outcomes of alternative phenotypes in varying environmental conditions. There are two types of melanin: eumelanins yield blackish hues, whereas pheomelanins yield reddish hues. The production of eumelanins requires low levels of glutathione (GSH), which is the most important intracellular antioxidant, whereas the production of pheomelanins requires high levels of GSH. We investigated the oxidative status of male pied flycatchers (Ficedula hypoleuca) with different degrees of melanin coloration under different temperatures during the nestling period. Moreover, we assessed the oxidative …
Temperature as a modulator of sexual selection
2018
A central question in ecology and evolution is to understand why sexual selection varies so much in strength across taxa; it has long been known that ecological factors are crucial to this. Temperature is a particularly salient abiotic ecological factor that modulates a wide range of physiological, morphological and behavioural traits, impacting individuals and populations at a global taxonomic scale. Furthermore, temperature exhibits substantial temporal variation (e.g. daily, seasonally and inter-seasonally), and hence for most species in the wild sexual selection will regularly unfold in a dynamic thermal environment. Unfortunately, studies have so far almost completely neglected the rol…
The evolution of sperm morphometry in pheasants
2007
7 pages; International audience; Post-copulatory sexual selection is thought to be a potent evolutionary force driving the diversification of sperm shape and function across species. In birds, insemination and fertilization are separated in time and sperm storage increases the duration of sperm-female interaction and hence the opportunity for sperm competition and cryptic female choice. We performed a comparative study of 24 pheasant species (Phasianidae, Galliformes) to establish the relative importance of sperm competition and the duration of sperm storage for the evolution of sperm morphometry (i.e. size of different sperm traits). We found that sperm size traits were negatively associat…
Quantitative genetics of sexual display, ejaculate quality and size in a lekking species.
2013
9 pages; International audience; The investment into extravagant sexual display and competitive sperm are two essential components of pre- and post-copulatory sexual selection. Even though the selective forces acting on sexual display and sperm characteristics have been extensively studied in recent years, the genetic architecture underlying the expression of these traits has been rarely explored. Here, we estimated the genetic variances and covariances of traits linked with ejaculate size and quality, and sexual display in the houbara bustard (Chlamydotis undulata undulata, Jacquin 1784). Using a very large pedigree-based data set, we show that sexual signalling and ejaculate size (but not…
Stabilizing natural selection on the early expression of a secondary sexual trait in a passerine bird
2004
Natural selection is a central tenet of evolutionary theory, yet the estimation of the direction and intensity of selection remains problematic. Here, we assess the strength of selection on the early expression of a secondary sexual ornament, bill colour, in male European blackbirds (Turdus merula) using 5 years of capture-mark-recapture (CMR) data. The best-fitting model consisted of a quadratic relationship between survival rate and bill colour, indicating stabilizing natural selection on the early expression of a secondary sexual trait. There was no evidence for sexual selection acting on bill colour in the first year. We suggest that the consideration of early selection and the adoption…