ABSTRACT
Background and Aims Rock outcrop vegetation is distributed worldwide and hosts a diverse, specialised, and unique flora that evolved under extremely harsh environmental conditions. The germination ecology in such ecosystems has received little attention, especially regarding the association between seed traits, germination responses and adult plants ecology. Here, we provide a quantitative and meta-analytical review of the seed functional ecology of Brazilian rocky outcrop vegetation, focusing on four vegetation types: campo rupestre, canga, campo de altitude and inselbergs.
Methods Using a database with functional trait data for 383 taxa and 10,187 germination records for 281 taxa, we calculated the phylogenetic signal of seven seed traits and tested whether they varied among growth forms, geographical distributions, and microhabitats. We also conducted a meta-analysis to understand the effects of light, temperature, and fire-related cues on the germination of campo rupestre species and how the beforementioned ecological groups and seed mass affect such responses.
Key Results All traits showed a strong phylogenetic signal. Campo rupestre species responded positively to light and had optimal germination between 20-30°C. The effect of temperatures below and above this range was modulated by growth form, with shrubs requiring and tolerating higher temperatures to germinate. We only found evidence of a moderating effect of seed mass for responses to heat shocks, with larger, dormant seeds tolerating heat better. Heat shocks above 200°C killed seeds, but smoke accelerated germination. No consistent differences in germination responses were found between restricted and widespread species or microhabitats. Still, species from xeric habitats evolved phenological strategies to synchronise germination with higher soil water availability.
Conclusions Evolutionary history plays a major role in the seed ecology of Brazilian rock outcrop vegetation. However, seed traits and germination responses did not explain species’ geographic distribution and microhabitats, suggesting other traits are more likely to explain such differences.
Competing Interest Statement
The authors have declared no competing interest.
