Maritime pine has many isolated and highly differentiated populations, ranging from stressful Mediterranean climates to benign Atlantic coastal areas in Southwestern Europe. Differentiation processes in phenotypic traits such as drought tolerance, reproductive behaviour and growth potential has been suggested to be adaptive. However little is known about the differentiation in defensive traits and strategies. In this paper we will summarize the results from several field and greenhouse experiments focused on identifying the sources of phenotypic variability of constitutive and inducible allocation to chemical defences in this model species. We have studied genetic variation within and across populations, resource availability and other factors such as ontogeny, within plant variation and herbivore identity. We usually find significant variation in defensive strategies across populations, and as well that families within populations differ in the constitutive and induced expression of defensive chemical traits. Particularly when analyzing terpenoids, we usually find high narrow sense heritability for the concentration of many individual terpenoids species. We also found that inducibility of those compounds (in response to real herbivory or methyl jasmonate application) is also usually genetically variable. Constitutive and inducible allocation to chemical defences are tissue specific, part specific and also compound specific and as well depends on the nature of the herbivore damage. Altogether, these results suggest that, in spite the pressure exerted by herbivores, existence of genetic variation in defensive traits is the common pattern in pine trees, and it is quantitatively relevant. However, although we have found that families differ in effective field resistance against several pests and pathogens, we usually fail to find significant genetic correlations among individual chemical traits and effective field resistance. Trade-offs between defences, between defensive strategies, and between defences and other life history traits have likely influenced the codifferentiation processes in defensive traits and strategies in this species.

Trabajo presentado en Estocolmo (Suecia) entre el 29 de junio y el 3 de julio de 2015.

Peer reviewed