Search results for "SYSTEMATICS"
showing 10 items of 6702 documents
Male health status, signalled by courtship display, reveals ejaculate quality and hatching success in a lekking species.
2010
8 pages; International audience; Summary 1. The information content of secondary sexual traits and the benefits gathered by choosy females are at the heart of sexual selection theory. Indicator models of sexual selection assume that secondary sexual traits reflect the phenotypic/genetic quality of their bearers and that females gather benefits from choosing these high-quality males. 2. Here, we tested the idea that courtship display reflects the health status in a bird species with a lek-based mating system, the houbara bustard (Chlamydotis undulata undulata). A group of males was treated with the lipopolysaccharide (LPS) of the cell wall of the bacterium Escherichia coli during the seasona…
Correlational selection on pro- and anti-inflammatory effectors.
2012
9 pages; International audience; Parasites impose a permanent threat for hosts. As a consequence, immune defenses are important for host fitness. However, the immune response can also produce self-damage and impair host fitness if not properly regulated. Effectors that up- and downregulate the immune response should, therefore, evolve in concert, and be under the action of correlational selection. To address this issue, we assessed the shape of the selection operating on pro- and anti-inflammatory effectors following an inflammatory challenge in laboratory mice. We found that selection acts on the combination of these two traits as individuals that produced large amount of pro-inflammatory …
Can number and size of offspring increase simultaneously?--a central life-history trade-off reconsidered.
2011
Abstract Background To maximize their fitness, parents are assumed to allocate their resources optimally between number and size of offspring. Although this fundamental life-history trade-off has been subject to long standing interest, its genetic basis, especially in wild mammals, still remains unresolved. One important reason for this problem is that a large multigenerational pedigree is required to conduct a reliable analysis of this trade-off. Results We used the REML-animal model to estimate genetic parameters for litter size and individual birth size for a common Palearctic small mammal, the bank vole (Myodes glareolus). Even though a phenotypic trade-off between offspring number and …
Island selection on mammalian life-histories: genetic differentiation in offspring size
2008
Abstract Background Since Darwin's pioneering work, evolutionary changes in isolated island populations of vertebrates have continued to provide the strongest evidence for the theory of natural selection. Besides macro-evolutionary changes, micro-evolutionary changes and the relative importance of natural selection vs. genetic drift are under intense investigation. Our study focuses on the genetic differentiation in morphological and life-history traits in insular populations of a small mammal the bank vole Myodes glareolus. Results Our results do not support the earlier findings for larger adult size or lower reproductive effort in insular populations of small mammals. However, the individ…
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…
Maternal investment in relation to sex ratio and offspring number in a small mammal - a case for Trivers and Willard theory?
2009
Summary 1. Optimal parental sex allocation depends on the balance between the costs of investing into sons vs. daughters and the benefits calculated as fitness returns. The outcome of this equation varies with the life history of the species, as well as the state of the individual and the quality of the environment. 2. We studied maternal allocation and subsequent fecundity costs of bank voles, Myodes glareolus, by manipulating both the postnatal sex ratio (all-male ⁄ all-female litters) and the quality of rearing environment (through manipulation of litter size by )2 ⁄ +2 pups) of their offspring in a laboratory setting. 3. We found that mothers clearly biased their allocation to female ra…
Sex-specific variation in the onset of reproduction and reproductive trade-offs in a boreal small mammal
2014
In seasonal environments, the optimal onset of reproduction plays a major role in defining the reproductive success of an individual. Environmental cues, like day length, weather conditions, and food, regulate the initiation and termination of the breeding season. Besides the interspecific variation in response to environmental cues, it has been suggested that due to different selection pressures, females and males can have different responses to environmental stimuli. However, this phenomenon has gained relatively little consideration, and the physiological mechanism behind these differences is not well known. Here, we report how two different environmental cues, variability of temperature…
Geographical trends in the yolk carotenoid composition of the pied flycatcher (Ficedula hypoleuca).
2010
Carotenoids in the egg yolks of birds are considered to be important antioxidants and immune stimulants during the rapid growth of embryos. Yolk carotenoid composition is strongly affected by the carotenoid composition of the female’s diet at the time of egg formation. Spatial and temporal differences in carotenoid availability may thus be reflected in yolk concentrations. To assess whether yolk carotenoid concentrations or carotenoid profiles show any large-scale geographical trends or differences among habitats, we collected yolk samples from 16 European populations of the pied flycatcher, Ficedula hypoleuca. We found that the concentrations and proportions of lutein and some other xantho…
Survival cost of an early immune soliciting in nature.
2009
8 pages; International audience; If immune functions confer obvious benefits to hosts, life-history theory assumes that they also induce costs, leading to trade-offs between immunity and other fitness components. However, whether substantial fitness costs are associated with immune systems in the wild is debatable, as numerous factors may influence the costs and benefits associated with immune activation. Here, we explore the survival cost of immune deployment in postfledging birds. We injected Eurasian collared dove nestlings (Streptopelia decaocto) with antigens from Escherichia coli, and examined whether this immune challenge affected survival after fledging. To assess survival, birds we…
Diversifying selection on MHC class I in the house sparrow (Passer domesticus).
2009
10 pages; International audience; Genes of the major histocompatibility complex (MHC) are the most polymorphic loci known in vertebrates. Two main hypotheses have been put forward to explain the maintenance of MHC diversity: pathogen-mediated selection and MHC-based mate choice. Host-parasite interactions can maintain MHC diversity via frequency-dependent selection, heterozygote advantage, and diversifying selection (spatially and/or temporally heterogeneous selection). In this study, we wished to investigate the nature of selection acting on the MHC class I across spatially structured populations of house sparrows (Passer domesticus) in France. To infer the nature of the selection, we comp…