We investigated the fitness consequences of specialization in an organism whose host choice has an immense impact on human health: the African malaria vector Anopheles gambiae s.s. We tested whether this mosquito’s specialism on humans can be attributed to the relative fitness benefits of specialist vs. generalist feeding strategies by contrasting their fecundity and survival on human‐only and mixed host diets consisting of blood meals from humans and animals. When given only one blood meal, An. gambiae s.s. survived significantly longer on human and bovine blood, than on canine or avian blood. However, when blood fed repeatedly, there was no evidence that the fitness of An. gambiae s.s. fed a human‐only diet was greater than those fed generalist diets. This suggests that the adoption of generalist host feeding strategies in An. gambiae s.s. is not constrained by intraspecific variation in the resource quality of blood from other available host species.

Within-host interactions among coinfecting parasites can have major consequences for individual infection risk and disease severity. However, the impact of these within-host interactions on between-host parasite transmission, and the spatial scales over which they occur, remain unknown. We developed and apply a novel spatially-explicit analysis to parasite infection data from a wild wood mouse (Apodemus sylvaticus) population. We previously demonstrated a strong negative interaction within individual hosts gastrointestinal parasites, the nematode Heligmosomoides polygyrus and the coccidia Eimeria hungaryensis, using drug-treatment experiments. Here, we find that this negative within-host interaction can significantly alter the between-host transmission dynamics of E. hungaryensis, but only within spatially-restricted neighbourhoods around each host. However, for the closely-related species E. apionodes, which experiments show does not interact strongly with H. polygyrus, we did not find any effect on transmission over any spatial scale. Our results demonstrate that the effects of within-host coinfection interactions can ripple out beyond each host to alter the transmission dynamics of the parasites, but only over local scales that likely reflect the spatial dimension of transmission. Hence there may be knock-on consequences of drug treatments impacting the transmission of non-target parasites, altering infection risks even for non-treated individuals in the wider neighbourhood.

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Community complexity-stability relationships have been at the centre of ecological thinking for many decades. MacArthur (1955) proposed a measure of stability that reflected the diversity in the number of pathways energy can flow up through a food web but how this index correlates with more formal ideas of dynamical stability remains unexplored. Here, we examine the relationship between MacArthurs proposed index and measures of local and global stability in Lotka-Volterra food web models. Our results provide support for MacArthurs intuitive hypothesis that increasing the diversity of energy pathways through food webs endows them with greater stability, as measured by both the probability of local and global point stabilities, and the return time to stable equilibria following perturbation.