Authors: Mario Díaz Anders P Møller Fernando J Pulido
Publish Date: 2003/03/18
Volume: 135, Issue: 3, Pages: 378-385
Abstract
Fruit abortion has been hypothesized to be a parental means of selective removal of propagules with low viability In particular aborted zygotes have been suggested to have developmentally deviant phenotypes and surviving offspring may therefore give rise to adults with a developmentally stable phenotype We tested predictions from this hypothesis using acorns of holm oaks Quercus ilex as a model system Fecundity of oak trees was negatively related to mean fluctuating asymmetry of leaves and abortion rates were positively related to leaf fluctuating asymmetry in at least one population Aborted acorns were asymmetric in 83–99 of cases in three samples while mature acorns were only asymmetric in 57–78 of cases Acorn asymmetry was unrelated to germination probability and germination date and had no significant effect on number of leaves leaf mass stem mass seedling height or leaf area of seedlings However acorn asymmetry affected the tradeoff between number and size of leaves in seedlings Seedlings from asymmetric acorns showed a positive relationship between acorn size and number of leaves but no relationships between acorn size and leaf area while symmetric acorns showed the opposite A positive relationship between acorn size and number of leaves in spring was found for naturally emerged seedlings that died during their first summer whereas the number of leaves produced by surviving seedlings did not depend on acorn size These findings are consistent with the hypothesis that stressed trees selectively abort propagules of low viability and that developmental selection acts on a measure of developmental instability of fruitsWe are very grateful to Hilda Fernández de Córdova † and Carlos Marcos for permission to work within their estates Chema Torres helped us during field work J Barandica F López and J V Zorrilla with leaf measurements and J Clobert with statistical tests Comments of M Polak G Moreno and two anonymous referees on earlier drafts were very helpful FJ P was funded by a FPI grant from the Consejería de Educación y Juventud of the Junta de Extremadura while carrying out the field work and M D received a grant for research of the Spanish CICYT while writing the manuscript This study is a contribution to the project PAC02008 of the Junta de Comunidades de CastillaLa Mancha
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