Functional trade-offs and ecological correlates of seed oil traits in alpine ecosystems.

Abstract

Seed oil content is a crucial energy reserve in angiosperms, with effects on biological functions and plant fitness, playing an important role in seed protection from environmental conditions. However, the eco-evolutionary role of seed oil traits in natural ecosystems is largely unexplored. We studied functional trade-offs and ecological drivers of seed oil traits in 47 species of an alpine flora. We analysed seed oil content and composition - relative proportion of unsaturated and saturated fatty acids (UFA/SFA) - and their relationships with seed mass, seed longevity, and germination timing. We also tested the response of seed oil traits to species' ecological preferences along microclimatic gradients. Seed oil content ranged from 1% to 34.2%, with the main variation explained by the UFA/SFA ratio, and little variation across altitude. Seed oil content significantly influenced seed longevity but had no relationships to seed mass and germination. Contrary to expectations, microclimatic gradients did not affect seed oil content or composition. All analyses showed strong phylogenetic constraints on seed oil traits. Seed oil traits in alpine species do not differ from those of other herbaceous species. A major trade-off between seed oil and seed longevity may help in understanding species regeneration in alpine soils and defining protocols for ex-situ conservation. The evolutionary conservatism of seed oil traits likely prevents seed-based selection of alpine species across altitudinal and microclimatic gradients.