Chronic malaria infections increase family inequalities and reduce parental fitness: experimental evidence from a wild bird population

Avian malaria parasites (Plasmodium) occur commonly in wild birds and are an increasingly popular model system for understanding host–parasite co‐evolution. However, whether these parasites have fitness consequences for hosts in endemic areas is much debated, particularly since wild‐caught individuals almost always harbour chronic infections of very low parasite density. We used the anti‐malarial drug Malarone^TM to test experimentally for fitness effects of chronic malaria infection in a wild population of breeding blue tits (Cyanistes caeruleus). Medication caused a pronounced reduction in Plasmodium infection intensity, usually resulting in complete clearance of these parasites from the blood, as revealed by quantitative PCR. Positive effects of medication on malaria‐infected birds were found at multiple stages during breeding, with medicated females showing higher hatching success, provisioning rates and fledging success compared to controls. Most strikingly, we found that treatment of maternal malaria infections strongly altered within‐family differences, with reduced inequality in hatching probability and fledging mass within broods reared by medicated females. These within‐brood effects appear to explain higher fledging success among medicated females and are consistent with a model of parental optimism in which smaller (marginal) offspring can be successfully raised to independence if additional resources become available during the breeding attempt. Overall, these results demonstrate that chronic avian malaria infections, far from being benign, can have significant effects on host fitness and may thus constitute an important selection pressure in wild bird populations.     

The rate of synonymous substitution in enterobacterial genes is inversely related to codon usage bias

Genes sequences from Escherichia coli, Salmonella typhimurium, and other members of the Enterobacteriaceae show a negative correlation between the degree of synonymous-codon usage bias and the rate of nucleotide substitution at synonymous sites. In particular, very highly expressed genes have very biased codon usage and accumulate synonymous substitutions very slowly. In contrast, there is little correlation between the degree of codon bias and the rate of protein evolution. It is concluded that both the rate of synonymous substitution and the degree of codon usage bias largely reflect the intensity of selection at the translational level. Because of the high variability among genes in rates of synonymous substitution, separate molecular clocks of synonymous substitution might be required for different genes.      

Trans‐generational effects on ageing in a wild bird population

Ageing, long thought to be too infrequent to study effectively in natural populations, has recently been shown to be ubiquitous, even in the wild. A major challenge now is to explain variation in the rates of ageing within populations. Here, using 49 years of data from a population of great tits (Parus major), we show that offspring life‐history trajectories vary with maternal age. Offspring hatched from older mothers perform better early in life, but suffer from an earlier onset, and stronger rate, of reproductive senescence later in life. Offspring reproductive lifespan is, however, unaffected by maternal age, and the different life‐history trajectories result in a similar fitness payoff, measured as lifetime reproductive success. This study therefore identifies maternal age as a new factor underlying variation in rates of ageing, and, given the delayed trans‐generational nature of this effect, poses the question as to proximate mechanisms linking age‐effects across generations.     

Conservation management of Lapwing Vanellus vanellus on lowland arable farmland in the UK

Lapwing Vanellus vanellus is known to be declining throughout much of its UK breeding range. The ecological requirements of the species are well known and a variety of mechanisms exist which can be implemented to help recovery. Arable options within agri-environment schemes can be used to provide breeding habitat throughout the species' UK range, and targeted recovery projects have been shown to have the potential to deliver increases in breeding pairs at the local level. The farming community need to be made aware of the requirements of Lapwing if agriculture and conservation needs are to be integrated.     

Absence of effects of predator control on nesting success of Northern Lapwings Vanellus vanellus: implications for conservation

The control of generalist predator populations is increasingly adopted as a management tool to combat declines in ground‐nesting bird populations. However, compensatory predation by uncontrolled species frequently occurs, so determining the relative impacts of different predatory species, and hence the relative benefits of their control, can be difficult. Islands, with their reduced faunas, provide natural experimental units for investigating specific predator–prey interactions in detail. We studied Northern Lapwing Vanellus vanellus breeding success on an island where feral Ferrets Mustela furo and Hooded Crows Corvus cornix were subjected to trial control regimes over 2 years. In both years, Lapwing hatching success was >80%, with neither Ferret nor Crow control selected as important predictors. Fledging rates in both years were 0.7 young per pair, despite highly effective predator removal, although Crow control potentially resulted in compensatory predation by Common Ravens C. corax. Neither mustelid nor corvid control produced significant immediate benefits for Lapwings. This suggests that mesopredator release of mustelids in mainland situations is unlikely to be a consistent threat to Lapwing, and provides further evidence that declines in this species are unlikely to be tackled successfully through predator management alone.