02532nas a2200205 4500008004100000022002500041245012500066210006900191260001600260300000800276520164400284653002401928653002901952653002701981653003802008653002502046100001802071700001902089856021802108 2023 eng d a0031-1820, 1469-816100aDefinitions of parasitism, considering its potentially opposing effects at different levels of hierarchical organization0 aDefinitions of parasitism considering its potentially opposing e cJul-03-2023 a1-83 a

Attachment file 96283.pdf online copy and file 96283 published.pdf published copy

 An annotated synthesis of textbook definitions of parasitism is presented. Most definitions declare parasitism is a long-lasting relationship between individuals of different species harming the hosts. The infection-induced costs are interpreted as diseases in the medical-veterinary literature. Alternatively, evolutionary ecologists interpret it as a reduction of host's fitness (longevity, fertility or both). Authors often assume that such effects decrease host population growth and select for antiparasitic defences, which is not necessarily true because infections may simultaneously express opposite effects at different levels of biological organization. (i) At the cellular level, infection-induced cell growth, longevity and multiplication may yield tumours maladaptive at higher levels. (ii) At the individual level, reduced host longevity, fertility or both are interpreted as disease symptoms or reduced fitness. (iii) Contrary to common sense, the growth rate of infected host lineages may increase in parallel with the individuals' reduced survival and fertility. This is because selection favours not only the production of more offspring but also their faster production. (iv) Finally, infections that reduce host individuals' or lineages' fitness may still increase infected host populations' growth rate in the context of ecological competition. Therefore, differences between parasitism and mutualism may depend on which level of organization one focuses on.

10acosts of parasitism10adefinition of parasitism10ahost population growth10alevels of biological organization10amultilevel selection1 aRózsa, Lajos1 aGaray, József uhttps://www.cambridge.org/core/journals/parasitology/article/definitions-of-parasitism-considering-its-potentially-opposing-effects-at-different-levels-of-hierarchical-organization/7E74E83AC630E3ED0A00DC4C3EDA7D64