Conifers include some of the biggest and longest-lived organisms on the planet. Therefore, their life history determinants (e.g. maintenance costs, reproduction and extent of life cycles) largely differ from those of most studied herbaceous and annual plants. As any other organism on Earth, conifers must finely tune the relative allocation of resources to growth, reproduction and defence, as balance of costs and benefits may change depending on the environmental context. Because resources are limited, conflicts in the allocation of resources may result into trade-offs among different functions at the individual level, leading to negative phenotypic correlations between life-history traits. But this kind of negative correlations can emerge also at the genetic level, imposing evolutionary constrains to the simultaneous improvement of the different functions. There is an increasing body of theoretical predictions about this framework, but little is still know in long-lived plants.
Here I report our results about trade-offs between life history traits in pine trees (particularly defensive trade-offs) from several greenhouse and field experiments performed during last years. In particular, we have studied genetic variation and phenotypic plasticity in growth, reproduction and defensive traits and strategies, and explored the existence of negative genetic correlations between those traits across families within populations, across populations within species, and across species within the genus Pinus. Constitutive-induced trade-offs are common in pine trees at different organization levels and they appear to be context-dependent. The existence of negative genetic correlations between pairs of traits may have important consequences to face current environmental forcing, and must be considered for the management of forest genetic materials in a changing environment.