title: Intercohort size structure dynamics of fire salamander larvae in ephemeral habitats: a mesocosm experiment.
abstract: The size structure of a larval population facilitates interaction asymmetries that, in turn, influence the dynamics of size-structure. In species that exhibit conspicuous aggressive interactions, the competitive effects of the smaller individuals may be overlooked. We manipulated initial size differences between two larval cohorts and young-cohort density of Salamandra infraimmaculata in mesocosms to determine: (1) whether young individuals function primarily as prey or as competitors of older and larger individuals; (2) the resulting dynamics of size variation; and (3) recruitment to the postmetamorph population. Intercohort size differences generally remained constant over time at low young-cohort densities, but reduced over time at high densities due to retardation of the old-cohort growth rate. This suggests a competitive advantage to the young cohort that outweighs the interference advantage of older cohorts previously documented in this species. The increase in mortality from desiccation due to high young-cohort density was an order of magnitude greater in the old cohort than in the young-cohort, further indicating size-dependent vulnerability to competition. However, the conditions least favorable to most of the old-cohort larvae (large size difference and high young-cohort density) promoted cannibalism. Among cannibals, mortality and time to metamorphosis decreased and sizes at metamorphosis increased substantially. Thus, a balance between the competitive advantage to young cohorts, and the interference and cannibalism advantage to old cohorts shapes larval size-structure dynamics. Larval densities and individual expression of cannibalism can shift this balance in opposite directions and alter relative recruitment rates from different cohorts.
authors.affiliation: Department of Evolutionary and Environmental Biology and the Institute of Evolution, Faculty of Natural Sciences, University of Haifa, 31905, Haifa, Israel. asaffield@gmail.com.|Department of Entomology, Hebrew University of Jerusalem, Rehovot, Israel. asaffield@gmail.com.
authors.forename: Asaf
authors.initials: A
authors.lastname: Sadeh
authors.affiliation: Department of Evolutionary and Environmental Biology and the Institute of Evolution, Faculty of Natural Sciences, University of Haifa, 31905, Haifa, Israel.
authors.forename: Antonina
authors.initials: A
authors.lastname: Polevikov
authors.affiliation: Department of Applied Mathematics and the Center for Stock Assessment, University of California, Santa Cruz, CA, 95064, USA.|Department of Biology, University of Bergen, Bergen, Norway.
authors.forename: Marc
authors.initials: M
authors.lastname: Mangel
authors.affiliation: Department of Evolutionary and Environmental Biology and the Institute of Evolution, Faculty of Natural Sciences, University of Haifa, 31905, Haifa, Israel.
authors.forename: Leon
authors.initials: L
authors.lastname: Blaustein
mesh_terms: D000818:Animals; D049628:Body Size; D002190:Cannibalism; D017753:Ecosystem; D007814:Larva / Q000033:anatomy & histology / Q000254:growth & development; D008675:Metamorphosis, Biological; D011156:Population Density; D011157:Population Dynamics; D012454:Salamandra / Q000033:anatomy & histology* / Q000254:growth & development
keywords: Amphibians; Exploitative competition; Fire salamander; Niche shifts; Priority effects