Climate and seed mass drive intraspecific variation in seed longevity in storage.

PREMISE: Conservation seed banks are essential for ex situ plant conservation, but stored seeds slowly deteriorate and lose viability. Seed longevity in storage is determined by the initial seed viability and the rate of seed viability loss. The rate of seed viability loss in storage varies between species and possibly between populations or even genotypes within species. However, the extent of this intraspecific variability and its drivers remain unclear.
METHODS: We investigated both inter- and intraspecific variability in seed longevity and its predictors in 41 common grassland species and 188 seed lots from across Europe. We exposed the seeds to simulated aging conditions (60% RH, 45°C) and used probit analysis to obtain the rate of seed viability loss (σ) as a measure of seed longevity. We then related σ to seed-lot- and species-specific factors.
RESULTS: Seed longevity (σ) varied significantly among seed lots within 58% of the species, and the probability of detecting such intraspecific differences increased with the number of seed lots available for a given species. This suggests that within-species variation in seed longevity is widespread. Seed-lot-specific predictors explained only 14.4% of the within-species variability. Specifically, seed longevity increased with the mean annual temperature at the seed lot origin and decreased with the seed-lot-specific seed mass. Across species, seed longevity differed among plant families but was unrelated to seed mass, protein, or oil content.
CONCLUSIONS: Our findings highlight substantial within-species variation in seed longevity in storage, but it is difficult to predict.