Pest defenses under weak selection exert a limited influence on the evolution of height growth and drought avoidance in marginal pine populations

The relevance of interpopulation variation in climate sensitivity highlighted that seed-source warm populations had greater adaptive capability than cold populations. In test sites, warming generated taller trees with higher δ13C and increased the evolutionary potential of height growth and δ13C across populations. We found, however, no pronounced gradient in defenses and their evolutionary potential along populations or test sites.

Response to selection was weak in defenses across test sites, but high for height growth, particularly at warm test sites. Response to selection of δ13C varied depending on its selective strength relative to height growth. We conclude that warming could promote the adaptability and evolvability of growth response and drought avoidance with limited evolutionary influence from pest (biotic) pressures.