Seed mass and population characteristics interact to determine performance of Scorzonera hispanica under common garden conditions

Many recent studies deal with within-species variation in seed mass and its consequences for plant growth. The possibility to explicitly separate the effects of population characteristics and seed mass are, however, usually hindered by availability of seeds of different size from different populations. We examined the effect of seed mass on germination, establishment, growth, and flowering of Scorzonera hispanica, a perennial herb. We used seeds of different masses from 20 populations, which differed greatly in size, habitat conditions, and genetic diversity. We selected seeds of the same range of seed masses from each population to ensure that all the variation in seed mass is represented within population.The results show, that at the population level, seed mass was enhanced only by habitat quality estimated using Beals index. Mass of seeds affected plant germination, but not subsequent growth. Growth of the plants was affected by genetic diversity of the populations. There were also several significant interactions between the effects of seed mass and genetic properties of the populations.Results of this study show that the effect of seed mass on plant germination and growth interacts with characteristics of the original population. This indicates that conclusions on the effect of seed mass derived using data from one or few populations only may not be representative. A range of populations should be examined before drawing conclusions on the seed mass–plant performance relationship.