Global Patterns in the Evolutionary Relations Between Seed Mass and Germination Traits

The relationship between seed mass and germination traits remains unresolved, with conflicting theoretical predictions. Some studies suggest larger seeds exhibit superior germination and post-germination performance, while others indicate the opposite, possibly due to environmental factors and additional seed traits. To clarify this relationship, we conducted a phylogenetically informed meta-analysis of 1889 plant species worldwide. Our findings show that seed dormancy is strongly associated with seed mass, but the direction and magnitude of this relationship vary by dormancy type, with lower seed mass in physiologically dormant seeds (-0.026) and higher seed mass in morphophysiologically (0.066) and physically dormant seeds (0.598). Trade-offs and correlated evolution have influenced seed mass, which exhibits notable phylogenetic conservation. Contrary to predictions, larger seeds did not consistently germinate faster or to a higher percentage (-0.648 and 0.890), likely due to interactions with growth form, dormancy class, and phylogenetic history. These findings highlight the importance of considering seed traits, growth form, and evolutionary relationships when examining plant adaptation and germination strategies.