Offspring fitness depends on interactions between parental care and environmental constraints. It has been suggested that in altricial birds parents are able to compensate for the detrimental effects of ectoparasites by improving food provisioning. We tested this prediction in a population of blue tits highly parasitized by blowfly larvae. The frequency of parental feeding visits was significantly higher in parasitized broods than in broods experimentally deparasitized. Despite a strong increase in parental care, chicks of parasitized broods were lighter, smaller, and more anaemic than chicks in deparasitized broods. Parents invest more in feeding parasitized young but cannot fully compensate for the negative effects of parasites, hence young are in poor condition at fledging.

We studied the effects of a doubling of atmospheric CO2 concentration on intact monoliths of Mediterranean grassland in growth chambers where climatic field conditions were simulated. During the six month growing season, changes in community structure were monitored by quantifying species richness and cover. The CO2 exchange of microcosms was measured continuously and the resulting quantity and quality of biomass were evaluated. Species richness and cover did not respond to elevated CO2. After one month of treatment, CO2 exchange measured during the day did not differ between CO2 levels but the night respiration was two‐fold higher under elevated CO2. Stimulations of both day and night CO2 flux by short‐term CO2 enrichment were recorded several times during the growing season. These results suggest that despite some downward adjustment of photosynthesis, net canopy photosynthesis was stimulated by elevated CO2, but this stimulation was compensated for by an increased respiration. The 20% stimulation of final phytomass under elevated CO2 was not significant: it resulted from unchanged live plant matter but a significant, 100% increase in litter accumulation. These results suggest that in low‐productivity Mediterranean herbaceous systems, the greatest effect of CO2 is not on the storage of carbon in biomass but on the turnover of the carbon in the plants.

Aim  Current climate change is supposed to be beneficial to many biological invaders, especially to C4 alien plants. While several experiments have been dedicated to measuring alien plants’ response to increased atmospheric CO2 concentration, very few studies have been undertaken to measure the response of alien plants to warming. This study was aimed to test experimentally whether the predicted climate change in the Mediterranean Basin could be beneficial to the alien C4 grass Setaria parviflora (Poir.) Kerguélen. Location  Three populations of S. parviflora from Corsica, southern France, were grown in Montpellier, southern France. Methods  The C4 alien grass S. parviflora was exposed to artificial climate change conditions for 3 years in open field and in competition with the local native community. We measured the response to artificial warming of +1.5 and +3 °C and artificial drought (−30% precipitation) versus ambient conditions for phenology, biomass and fecundity of S. parviflora. We compared the response of S. parviflora individuals to the response of the local community. Results  Artificial warming strongly enhanced the biomass and the fecundity of S. parviflora, while it decreased or did not affect the biomass and fecundity of the local community. The phenology (onset of growth, first spike pollinating and fruit ripeness) of S. parviflora was advanced significantly and explained the changes observed in biomass and fecundity. Main conclusions  Here, we report a positive effect of climate change on the growth and fertility of S. parviflora, a C4 alien plant. Our results suggest that climate change predicted for the next decades in the Mediterranean Basin might substantially enhance the performance of S. parviflora, potentially increasing its invasion success.