title: Competition and the evolution of reproductive restraint in malaria parasites.
abstract: All organisms must trade off resource allocation between different life processes that determine their survival and reproduction. Malaria parasites replicate asexually in the host but must produce sexual stages to transmit between hosts. Because different specialized stages are required for these functions, the division of resources between these life-history components is a key problem for natural selection to solve. Despite the medical and economic importance of these parasites, their reproductive strategies remain poorly understood and often seem counterintuitive. Here, we tested recent theory predicting that in-host competition shapes how parasites trade off investment in in-host replication relative to between-host transmission. We demonstrate, across several genotypes, that Plasmodium chabaudi parasites detect the presence of competing genotypes and facultatively respond by reducing their investment in sexual stages in the manner predicted to maximize their competitive ability. Furthermore, we show that genotypes adjust their allocation to sexual stages in line with the availability of exploitable red blood cell resources. Our findings are predicted by evolutionary theory developed to explain life-history trade-offs in more traditionally studied multicellular taxa and suggest that the answer to the long-standing question of why so few transmission stages are produced is that in most natural infections heavy investment in reproduction may compromise in-host survival.
authors: Institute of Evolutionary Biology, University of Edinburgh, School of Biological Sciences, United Kingdom. laura.pollitt@ed.ac.uk
authors: Laura C
authors: LC
authors: Pollitt
authors: Nicole
authors: N
authors: Mideo
authors: Damien R
authors: DR
authors: Drew
authors: Petra
authors: P
authors: Schneider
authors: Nick
authors: N
authors: Colegrave
authors: Sarah E
authors: SE
authors: Reece
mesh_terms: D000818:Animals; D005075:Biological Evolution; D003163:Competitive Behavior; D005718:Gametogenesis; D014644:Genetic Variation; D005838:Genotype; D008288:Malaria / Q000469:parasitology* / Q000635:transmission*; D008297:Male; D008675:Metamorphosis, Biological; D051379:Mice; D056265:Microbial Interactions; D010641:Phenotype; D016788:Plasmodium chabaudi / Q000235:genetics* / Q000254:growth & development / Q000502:physiology*; D012098:Reproduction