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.
Bibliographical noteFunding Information:
Many thanks to Arik Kershenbaum, Lior Blank, Michal Segoli, Orr Spiegel, and Tobin Northfield for their feedback on the manuscript. This study was funded by Israel Science Foundation grant (961-2008) awarded to LB, and by Postdoctoral Award No. FI-457-2011 from BARD, The United States-Israel Binational Agricultural Research and Development Fund, awarded to AS. The study was carried out in accordance with the Israeli Nature and Parks Authority permit 2010/37885, and with the University of Haifa Animal Experimentation Ethics Committee permit 212/11.
© 2015, Springer-Verlag Berlin Heidelberg.
- Exploitative competition
- Fire salamander
- Niche shifts
- Priority effects
ASJC Scopus subject areas
- Ecology, Evolution, Behavior and Systematics