Phylogeography and genetic structure of the red-legged partridge (Alectoris rufa): more evidence for refugia within the Iberian glacial refugium

The Pleistocene climatic oscillations promoted the diversification in avian species during the last glacial period. The red‐legged partridge (Alectoris rufa, Family Phasianidae) has a large natural distribution extending from the Mediterranean to humid temperate zones. However, the genetic structure for this species is unknown. The present study investigates the phylogeography, genetic structure and demographic history of A. rufa across its distribution, employing both mitochondrial DNA control region sequences and nuclear microsatellite loci. Our results propose that this species was greatly affected by Pleistocene glaciations. The mismatch analyses suggest that the current populations resulted from post‐glacial expansion and subsequent differentiation resulting in five diagnosable genetic clusters: Southwestern, Central‐eastern, Northwestern, Balearic and French and Italian. Further, we found evidence of three glacial refugia within the currently recognized Iberian glacial refugium. The intraspecific structure revealed by both maternal and biparental phylogeographic analyses was not resolved in the phylogenetic analyses. Based on all considerations, we recommended that five management units be recognized.     

Determinants of age-dependent change in a secondary sexual character

Many secondary sexual characters vary in a systematic way with the age of individuals, with young and old individuals displaying at lower levels than individuals of intermediate age. Analyses quantifying the within-individual and among-individual components of phenotypic variation can help partition effects of phenotypic plasticity and selective mortality. We analysed phenotypic variation in the expression of a secondary sexual character, tail length, in male and female barn swallows Hirundo rustica from four European populations studied during 11-26 years, using linear mixed effect models to describe age-related expression. Tail length increased from yearlings to intermediate aged birds with a subsequent decrease at old age. In males, this age-related pattern was because of both within-subject and between-subject effects, with no difference among populations. Males having longer lifespan had shorter tails when young than those having shorter lifespan. Females showed similar patterns of age-related variation as males, with no difference among populations. The major difference between sexes was that the between-subject effects (i.e. disappearance effects or selection) were much more important for males compared to females for which lifetime variation in tail length was mainly because of a within-subject effect (i.e., a plastic response). These findings suggest that whereas males trade greater expression of the secondary sexual character at young age against longevity, that was not the case for females. This is consistent with tail length being more costly in males than in females, with the cost of long tails potentially being offset by elevated mating success, whereas that is not the case in females.     

The fitness of drug-resistant malaria parasites in a rodent model: multiplicity of infection

Malaria infections normally consist of more than one clonally replicating lineage. Within-host interactions between sensitive and resistant parasites can have profound effects on the evolution of drug resistance. Here, using the Plasmodium chabaudi mouse malaria model, we ask whether the costs and benefits of resistance are affected by the number of co-infecting strains competing with a resistant clone. We found strong competitive suppression of resistant parasites in untreated infections and marked competitive release following treatment. The magnitude of competitive suppression depended on competitor identity. However, there was no overall effect of the diversity of susceptible parasites on the extent of competitive suppression or release. If these findings generalize, then transmission intensity will impact on resistance evolution because of its effect on the frequency of mixed infections, not because of its effect on the distribution of clones per host. This would greatly simplify the computational problems of adequately capturing within-host ecology in models of drug resistance evolution in malaria.     

Phenotypic gender variation within inflorescences of the protogynous species Helleborus foetidus L. (Ranunculaceae)

In the protogynous species H. foetidus, I investigated if investment in sexual structures and seed set shows any trend with position in the flower-opening sequence. In four-flower inflorescences, stamen number decreased with flower position i.e. was highest for the earliest flower and lowest for the latest flower. Ovule number was significantly higher in the latest flower. Stamen and ovule number did not covary, indicating that there is no structural gender trade-off in this species. Seed set (i.e. percentage of ovules producing seed) did not differ between control plants and pollen-supplemented plants and the effect of pollen supplementation did not vary among positions. Seed set showed marginally significant differences between control plants and simulated-herbivory plants, but the effects of this treatment varied significantly among positions. Significant among-position variation in seed set was observed in the control plants but not the simulated-herbivory plants. Seed set of latest-opening flowers of simulated-herbivory plants was significantly higher than that of latest-opening flowers of control plants. H. foetidus support Brunet and Charlesworth's (1995) prediction that in plants with protogynous flowers, later-opening flowers should specialize as female flowers, at least under conditions of high resource availability.     

Spiteful interactions between sympatric natural isolates of Xenorhabdus bovienii benefit kin and reduce virulence

Spite occurs when an individual harms itself in the act of harming others. Spiteful behaviour may be more pervasive in nature than commonly thought. One of the clearest examples of spite is the costly production and release of bacteriocins, antimicrobial toxins noted for their ability to kill conspecifics. A key question is to what extent these toxins provide a fitness advantage to kin of the producer cell, especially in natural communities. Additionally, when bacteria are involved in parasitic relationships, spiteful interactions are predicted to lower bacterial densities within a host, causing a reduction in parasite-induced virulence. Using five sympatric, field-collected genotypes of the insect pathogen Xenorhabdus bovienii, we experimentally demonstrate that bacteriocin production benefits kin within the host, and that it slows the mortality rate of the host. These results confirm that spite among naturally coexisting bacterial clones can be a successful kin-selected strategy that has emergent effects on virulence.     

The impact of immunization on competition within Plasmodium infections

Evolutionary theory argues that ecological interactions between pathogens within an infection can be a potent source of selection shaping traits such as virulence, drug resistance, and infectiousness. In humans, malaria infections are frequently genetically diverse, with mixed genotype infections the norm. A wide variety of evidence shows that crowding occurs within infections, with the population densities of individual genotypes suppressed by the presence of others. Public health interventions are expected to impact on levels of immunity experienced by pathogens, indirectly by reducing the rate of acquisition of natural immunity by reducing the force of infection, and directly in the case of vaccination programs. Here we ask how enhanced host immunity affects competitive interactions between malaria parasites within hosts and thus the strength of in-host selection on traits such as virulence. We used a model malaria system, Plasmodium chabaudi in laboratory mice, where it has been previously shown that less virulent parasites are competitively suppressed by more virulent strains, generating within-host selection for increased virulence. We found that immunization with either a recombinant antigen or with live parasites suppressed parasite densities, but that there was no evidence that immunization relieved or exacerbated competitive suppression, or affected the relative frequency of clones within infections. There is thus no reason to think that immunization strengthens or alleviates the potentially very potent selection on parasite traits arising from interactions between pathogen genotypes within infections.     

Competing for blood: the ecology of parasite resource competition in human malaria–helminth co‐infections

Ecological theory suggests that co‐infecting parasite species can interact within hosts directly, via host immunity and/or via resource competition. In mice, competition for red blood cells (RBCs) between malaria and bloodsucking helminths can regulate malaria population dynamics, but the importance of RBC competition in human hosts was unknown. We analysed infection density (i.e. the concentration of parasites in infected hosts), from a 2‐year deworming study of over 4000 human subjects. After accounting for resource‐use differences among parasites, we find evidence of resource competition, priority effects and a competitive hierarchy within co‐infected individuals. For example reducing competition via deworming increased Plasmodium vivax densities 2.8‐fold, and this effect is limited to bloodsucking hookworms. Our ecological, resource‐based perspective sheds new light into decades of conflicting outcomes of malaria–helminth co‐infection studies with significant health and transmission consequences. Beyond blood, investigating within‐human resource competition may bring new insights for improving human health.     

Transgenerational plasticity and climate change experiments: Where do we go from here?

Phenotypic plasticity, both within and across generations, is an important mechanism that organisms use to cope with rapid climate change. While an increasing number of studies show that plasticity across generations (transgenerational plasticity or TGP) may occur, we have limited understanding of key aspects of TGP, such as the environmental conditions that may promote it, its relationship to within‐generation plasticity (WGP) and its role in evolutionary potential. In this review, we consider how the detection of TGP in climate change experiments is affected by the predictability of environmental variation, as well as the timing and magnitude of environmental change cues applied. We also discuss the need to design experiments that are able to distinguish TGP from selection and TGP from WGP in multigenerational experiments. We conclude by suggesting future research directions that build on the knowledge to date and admit the limitations that exist, which will depend on the way environmental change is simulated and the type of experimental design used. Such an approach will open up this burgeoning area of research to a wider variety of organisms and allow better predictive capacity of the role of TGP in the response of organisms to future climate change.     

Plant Regeneration from Barly (Hordeum vulgare) Immature Inflorescences Cryopeserved by Vitrification

Vitrification is a new technique of cryopreservation. Immature inflorescences of barley (Hordeum Vulgate L. ) were precultured in medium supplemented with 0. 5 mol/L sucrose for 2 days and dehydrated in PVS2 at 0 ℃ for 5 min before plunged into liquid nitrogen. After rapid warming and unloading, the survival of three cultivars "81Gl", "Gebeina", and "Xu 9" was 100%, 82.5% and 50% respectively. Callus formation and plant regeneration was achieved from recovered inflorescences. The non-precultured samples could not survival in liquld nitrogen. Desiccation-tolerance and freeze-tolerance affected plant survival. Vitrification shared the advantages of high levels of survival, short period of lag stage and complete viability of cryopreserved organs.     

单元内混合家系相关法和阈性状法估计遗传力的比较研究

本文提出了一种估计遗传力的方法即单元内混合家系相关法,并用这种方法及阈性状分析法进行了猪肢蹄结实度的遗传力估计,结果表明,对于多阈性状,用单元内混合家系相关法估计的结果准确性好。