title: Intrinsic worker mortality depends on behavioral caste and the queens' presence in a social insect.
abstract: According to the classic life history theory, selection for longevity depends on age-dependant extrinsic mortality and fecundity. In social insects, the common life history trade-off between fecundity and longevity appears to be reversed, as the most fecund individual, the queen, often exceeds workers in lifespan several fold. But does fecundity directly affect intrinsic mortality also in social insect workers? And what is the effect of task on worker mortality? Here, we studied how social environment and behavioral caste affect intrinsic mortality of ant workers. We compared worker survival between queenless and queenright Temnothorax longispinosus nests and demonstrate that workers survive longer under the queens' absence. Temnothorax ant workers fight over reproduction when the queen is absent and dominant workers lay eggs. Worker fertility might therefore increase lifespan, possibly due to a positive physiological link between fecundity and longevity, or better care for fertile workers. In social insects, division of labor among workers is age-dependant with young workers caring for the brood and old ones going out to forage. We therefore expected nurses to survive longer than foragers, which is what we found. Surprisingly, inactive inside workers showed a lower survival than nurses but comparable to that of foragers. The reduced longevity of inactive workers could be due to them being older than the nurses, or due to a positive effect of activity on lifespan. Overall, our study points to behavioral caste-dependent intrinsic mortality rates and a positive association between fertility and longevity not only in queens but also in ant workers.
authors.affiliation: Institute of Organismic and Molecular Evolution, Johannes Gutenberg University Mainz, Johannes von Müller Weg 6, 55128, Mainz, Germany. philip.gueler@gmail.com.
authors.forename: Philip
authors.initials: P
authors.lastname: Kohlmeier
authors.affiliation: Institute of Organismic and Molecular Evolution, Johannes Gutenberg University Mainz, Johannes von Müller Weg 6, 55128, Mainz, Germany.
authors.forename: Matteo Antoine
authors.initials: MA
authors.lastname: Negroni
authors.affiliation: Institute of Organismic and Molecular Evolution, Johannes Gutenberg University Mainz, Johannes von Müller Weg 6, 55128, Mainz, Germany.
authors.forename: Marion
authors.initials: M
authors.lastname: Kever
authors.affiliation: Institute of Organismic and Molecular Evolution, Johannes Gutenberg University Mainz, Johannes von Müller Weg 6, 55128, Mainz, Germany.
authors.forename: Stefanie
authors.initials: S
authors.lastname: Emmling
authors.affiliation: Institute of Organismic and Molecular Evolution, Johannes Gutenberg University Mainz, Johannes von Müller Weg 6, 55128, Mainz, Germany.
authors.forename: Heike
authors.initials: H
authors.lastname: Stypa
authors.affiliation: Senckenberg Biodiversity and Climate Research Centre, Senckenberg Gesellschaft für Naturforschung, Senckenberganlage 25, D-60325, Frankfurt am Main, Germany.
authors.forename: Barbara
authors.initials: B
authors.lastname: Feldmeyer
authors.affiliation: Institute of Organismic and Molecular Evolution, Johannes Gutenberg University Mainz, Johannes von Müller Weg 6, 55128, Mainz, Germany.
authors.forename: Susanne
authors.initials: S
authors.lastname: Foitzik
mesh_terms: D000818:Animals; D001000:Ants / Q000502:physiology*; D001522:Behavior, Animal / Q000502:physiology*; D005260:Female; D008136:Longevity / Q000502:physiology*; D012098:Reproduction / Q000502:physiology; D012919:Social Behavior
keywords: Division of labor; Fecundity; Intrinsic mortality; Life history; Social insects; Survival; Trade-offs