Variation in seed packaging of a fleshy-fruited conifer provides insights into the ecology and evolution of multi-seeded fruits

The study of intraspecific seed packaging (i.e. seed size/number strategy) variation across different populations may allow a better understanding of the ecological forces that drive seed evolution in plants. Juniperus thurifera (Cupressaceae) provides a good model to study this due to the existence of two subspecies differentiated by phenotypic traits, such as seed size and cone seediness (number of seeds inside a cone) across its range. The aim of this study was to analyse seed packaging (seed mass and cone seediness) variation at different scales (subspecies, populations and individuals) and the relationship between cone and seed traits in European and African J. thurifera populations. After opening more than 5,300 cones and measuring 3,600 seeds, we found that seed packaging traits followed different patterns of variation. Large-scale effects (region and population) significantly contributed to cone seediness variance, while most of the seed mass variance occurred within individuals. Regarding variation in cone seediness, we validated previous reports on the intraspecific differences in of J. thurifera seed packaging between the two sides of the Mediterranean Sea, with African cones bearing fewer but larger seeds than the European ones. However, no differences in seed mass were found between populations when taking into account cone seediness; thus, both subspecies followed the same seed size/number trade-off. Regarding variation in individual seed mass, larger cones contained more pulp and seeds and displayed a larger variation in seed mass, revealing that the positive relationship between seed and cone sizes may not be straightforward. We hypothesize that the large variation of seed size found within cones and individuals in J. thurifera, but as well in other fleshy-fruited species, could represent a bet-hedging strategy for dispersal. This article is protected by copyright. All rights reserved.