AOBPreview originally published online on June 17, 2007
Annals of Botany 2007 100(2):325-334; doi:10.1093/aob/mcm112
Field Patterns of Leaf Plasticity in Adults of the Long-lived Evergreen Quercus coccifera
1 Departamento de Biología Vegetal I, Universidad Complutense de Madrid, José Antonio Novais 2, 28040 Madrid, Spain
2 Real Jardín Botánico de Madrid, CSIC, Plaza Murillo 2, 28014 Madrid, Spain
3 Departamento de Ecología, Universidad Complutense de Madrid, José Antonio Novais 2, 28040 Madrid, Spain
4 Centro de Ciencias Medioambientales, CSIC, Serrano 115 Dpdo., 28006 Madrid, Spain
5 Departamento de Edafología, Universidad Complutense de Madrid, Pza. Ramón y Cajal S/N, 28040, Madrid, Spain
* For correspondence. E-mail balaguer{at}bio.ucm.es
Received: 9 December 2006 Returned for revision: 26 February 2007 Accepted: 25 April 2007 Published electronically: 17 June 2007
Background and Aims Quercus coccifera,: as a long-lived sprouter, responds plastically to environmental variation. In this study, the role of foliar plasticity as a mechanism of habitat selection and modification within the canopy and across contrasted habitats was characterized. An examination was made of the differential contribution of inner and outer canopy layers to the crown plasticity expressed in the field by adult individuals and its dependence on environmental and genetic factors.
Methods: Within-crown variation in eight foliar traits was examined in nine populations dominated by Q. coccifera. The difference between mean trait values at the inner and outer canopy layers was used as a proxy for crown plasticity to light. Correlations between geographic distances, environmental differences (climatic and edaphic) and phenotypic divergence (means and plasticities) were assessed by partial Mantel tests. A subset of field measurements was compared with data from a previous common garden experiment.
Key Results: Phenotypic adjustment of sun leaves contributed significantly to the field variation in crown plasticity. Plasticity in leaf angle, lobation, xanthophyll cycle pigments and ß-carotene content was expressed in sun and shade leaves concurrently and in opposite directions. Phenotypic plasticity was more strongly correlated with environmental variation than mean trait values. Populations of taller plants with larger, thinner (higher specific leaf area) and less spiny leaves exhibited greater plasticity. In these populations, the midday light environment was more uniform at the inner than at the outer canopy layers. Field and common garden data ranked populations in the same order of plasticity.
Conclusions: The expression of leaf plasticity resulted in a phenotypic differentiation that suggests a mechanism of habitat selection through division of labour across canopy layers. Signs of plasticity-mediated habitat modification were found only in the most plastic populations. Intracanopy plasticity was sensitive to environmental variation but also exhibited a strong genetic component.
Key words: Habitat selection, habitat modification, leaf morphology, niche construction, phenotypic plasticity, population divergence, resprouter, within-crown division of labour, xanthophylls