title: A facultative ectoparasite attains higher reproductive success as a parasite than its free-living conspecifics.
abstract: Comparative and phylogenetic studies reveal that parasites evolved from free-living ancestors, but the underlying processes and mechanisms are not well understood. In order for selection to favor the evolution of parasitism, there must be pre-existing adaptations for host exploitation and a fitness advantage favoring the transition to parasitism. Here, we experimentally investigate the differential reproductive success of a facultative parasite, Macrocheles subbadius. Lifetime reproductive success was higher among female mites that fed on fruit fly hemolymph as parasites compared to free-living mites. The per capita lifetime fecundity for parasitic females was 2.4 times that of free-living females. The offspring sex ratio also differed between the two modes of life, with parasitic mites producing more sons and hence a relatively weaker female-biased sex ratio (0.61) than mites that were free-living (0.94). These results suggest that parasitic female mites allocate more resources to egg production, and were limited by sperm rather than food, as was the case with free-living mites. The higher lifetime reproductive success of mites that opportunistically feed on host hemolymph provides the fitness advantage necessary for the evolution of parasitism.
authors.affiliation: Department of Biological Sciences, University of Alberta, CW405 Biological Sciences Bldg., Edmonton, AB, T6G 2E9, Canada. lluong@ualberta.ca.
authors.forename: Lien T
authors.identifier: http://orcid.org/0000-0003-4350-4164
authors.initials: LT
authors.lastname: Luong
authors.affiliation: Department of Biological Sciences, University of Alberta, CW405 Biological Sciences Bldg., Edmonton, AB, T6G 2E9, Canada.
authors.forename: Dewmi
authors.initials: D
authors.lastname: Subasinghe
mesh_terms: D000818:Animals; D005075:Biological Evolution; D004330:Drosophila / Q000469:parasitology; D005260:Female; D005298:Fertility; D008297:Male; D008925:Mites / Q000502:physiology*; D012098:Reproduction
keywords: Drosophila; Evolution of parasitism; Facultative parasitism; Fecundity; Lifetime reproductive success; Macrocheles; Sex-ratio