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Abstract. Malaria parasites are a major cause of human mortality in tropical countries and a potential threat for wildlife, as witnessed by the malaria-induced extinction of naive Hawaiian avifauna. Identifying resistance mechanisms is therefore crucial both for human health and wildlife conservation. Patterns of malaria resistance are known to be highly polygenic in both humans and mice, with marked contributions attributed to major histocompatibility (Mhc) genes. Here we show that specific Mhc variants are linked to both increased resistance and susceptibility to malaria infection in a wild passerine species, the house sparrow (Passer domesticus). In addition, links between host immunogenetics and resistance to malaria involved population-specific alleles, suggesting local adaptation in this hostparasite interaction. This is the first evidence for a population-specific genetic control of resistance to malaria in a wild species.

The terminal investment hypothesis predicts that individuals should invest more in their present reproduction if they are less likely to survive to future reproductive events. Infections, which reduce viability, may be used by individuals as a cue of a diminishing residual reproductive value and could therefore theoretically trigger an intensification of breeding effort. We tested this hypothesis in a natural population of house sparrows (Passer domesticus). We manipulated the immune system of breeding females by injecting them with a vaccine against the Paramyxo virus, the agent of Newcastle disease. Females were captured and treated immediately after completion of their first clutch either with the vaccine (NDV) or with phosphate buffered saline (PBS). The entire clutch was subsequently removed. We also screened Mhc class I genes of females to assess possible genotype‐by‐immune treatment interactions on reproductive investment. Our results indicate that vaccinated females were more likely to lay replacement clutches and that the difference in number of eggs between first and replacement clutches was greater for NDV females than for controls. In addition, chick size, both in terms of tarsus length and body mass, was affected by immune activation but in interaction with nestling age and female body mass, respectively. Mhc genotype‐by‐immune treatment interactions were never significant; however, allelic diversity was positively correlated with nestling survival. These results show that immune system activation is potentially used as a cue of reduced survival prospect and appears to induce a costly terminal investment behavior, and Mhc diversity might be under selection in a natural population of house sparrows.

We used quantitative genetic arzalyses to test the hypothesis of a trade-off between locomotor speed azzd erzdurance in a population of the European lizard Lacerta vivipara, which is the subject of long-term demographic studies. We estimated the heritability of maximal sprirzt speed, treadmill endurance, and tail length, a morphometric trait that may afect locomotor performance, as well asphenotypic, genetic, and erzvironmerztal correlatiorzs between these traits. Gravid females were captured in the field arzd held in the laboratory under standardized conditions until giving birth; traits were then measured on their offspring. Prior to genetic analyses, we used multiple regressions to remove the effects of such covariates as body size (mass and snout-vent length), dam age, and length of time dams were held in captivity prior to parturition. When we examined the residual characters, heritability was low and statistically nonsignz~kant for speed but relatively high for both endurance (0.46) and tail length (0.51). None of thephenotypic, genetic, or erzziironmental correlations between traits was statistically sig-nijica~zt. Thus, we found no evidence for a trade-off between speed and endurance; these results are consistent with those reported in two previous studies of squamate reptiles (the garter snake Thamnophis sirtalis and the fence lizard Sceloporus occidentalis). The lack of a 7zegatiz)e genetic correlation between speed and erzdurarzce suggests that these aspects of locomotor abilities are rela-tiz~elj, free to evolve independently, such that natural selection could irzcrease both speed and endurance. However, the species studied to date have low to moderate capacities for speed and endurance, as compared with other squamates. Phj~siologically based trade-offs-for example, those caused by the composition of muscle$ber types-should be more likely to exist in species that have high capacities for speed and/or endurance.

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