The role of maternal age, growth and environment in shaping offspring performance in an aerial conifer seed bank

Abstract

PREMISE Maternal effects have been demonstrated to affect offspring performance in many organisms and, in plants, seeds are important mediators of these effects. Some woody plant species maintain long-lasting canopy seed banks as an adaptation to wildfires. Importantly, these seeds stored in serotinous cones are produced by the mother plant under varying ontogenetic and physiological conditions.

METHODS We sampled the canopy seed bank of a highly serotinous Pinus pinaster population to test if maternal age and growth, as well as the environmental conditions during each crop year, affected seed mass and ultimately germination and early survival. After determining retrospectively the year of each seed cohort, we followed germination and early survival in a semi-natural common garden.

KEY RESULTS We found that seed mass was related to maternal age and growth at the time of seed production, i.e. slow growth-older mothers had smaller seeds and fast growth-young mothers had bigger seeds, which could be interpreted either as a proxy of senescence or as a maternal strategy. We also confirmed that seed mass had a positive effect on germination success, but beyond differences in seed mass, maternal age had a negative effect and diameter had a positive effect on germination timing and subsequent survival.

CONCLUSIONS Thereby we highlight the importance of maternal conditions combined with seed mass in shaping seedling establishment. Our findings open new insights in the offspring performance deriving from long-term canopy seed banks, which may have high relevance for plant adaptation.