Resumen 3.4.1.1. Site effect on tree growth, survival and reproduction 3.4.1.2. Plastic, allometric and genetic effects on cone serotiny and canopy cone bank 3.4.2. Maintenance costs of serotiny (Study II) 3.4.2.1. Cone-opening laboratory screening experiment  Plant material and protocol   Data analysis  3.4.2.2. Manipulating water availability of serotinous cones ex situ  Plant material and protocol   Data analysis  3.4.2.3. Manipulating tree to cone physical connection in situ  Plant material and protocol   Data analysis  3.4.3. Bark absolute thickness and bark allocation variation among sites and populations (Study III) 3.4.3.1. Plastic and genetic effects on bark thickness at breast and basal height 3.4.3.2. Relationship of bark thickness with seed source environment 3.4.3.3. Allometric, plastic and genetic effects on bark allocation 3.4.4. Adaptive variation in P. halepensis: population differentiation and phenotypic integration (Study IV) 3.4.4.1. Trait trade-offs 3.4.4.2. Trait-environment associations 3.4.4.3. Quantitative genetic differentiation 3.4.4.4. Neutral vs. Adaptive differentiation 4. Results 4.1. Variation of serotiny degree and aerial seedbank among sites and populations (Study I) 4.1.1. Site effect on tree growth, survival and reproduction 4.1.2. Plastic and allometric effects on cone serotiny 4.1.3. Population effects and interactions with site and size on cone serotiny 4.1.4. Population x site effects on the canopy cone bank 4.2. Maintenance costs of serotiny (Study II) 4.2.1. Physiological condition of serotinous cone peduncle in Pinus halepensis 4.2.2. Cone-opening laboratory screening experiment 4.2.3. Manipulating water availability of serotinous cones ex situ 4.2.4. Manipulating tree to cone physical connection in situ 4 4.3. Bark absolute thickness and bark allocation variation among sites and populations (Study III) 4.3.1. Plastic and genetic effects on bark thickness at breast and basal height 4.3.2. Relationship of bark thickness with seed source environment 4.3.3. Allometric, plastic and genetic effects on bark allocation 4.4. Adaptive variation in P.