Differentiation of the Seed Regeneration Niche Along a Small‐Scale Plant Zonation in Mediterranean Temporary Ponds

Aims: Regeneration by seed is regarded as a key stage to understand plant community processes and vegetation patterns. In this study, we tested the hypothesis that the seed regeneration niche exhibits differentiation along the small-scale plant zonation that characterizes the ephemeral vegetation of Mediterranean temporary ponds (MTPs). Location: MTPs of Sicily, Italy, southern Europe. Methods: Seeds of 13 MTPs species were collected along the zonation. Experiments were conducted to measure seed germination responses to different levels of temperature (constant and alternating), light, and after-ripening. Cardinal temperatures for germination (base Tb, optimal Td, ceiling Tc) were calculated following a thermal-time approach. Analyses were applied to (1) test germination responses as a function of the zonation and (2) describe the shape of the germination niche across zones. Results: Germination temperatures significantly varied along the zonation, with species from the outer belt having higher Td (> 24.5°C) and Tc (> 30°C) than species from flooded areas. Species from the long-lasting flooded area showed the highest germination in darkness (> 75% in some cases). Alternating temperatures and after-ripening had a general positive effect across zones. Ordination analysis indicated a high variability of light and alternating temperature preferences in species from short-lasting flooded areas. Conclusions: Our results support the hypothesis that temperature and light preference for germination vary across a small-scale plant zonation in MTPs. This allows species from the outer belt to be among the first to germinate, whereas species from long-lasting flooded areas can germinate even under turbid water. The different light and alternating temperature preferences of species from short-term flooded areas may be an adaptation to cope with water fluctuations. This study confirms the importance of considering seed germination traits in the effort to understand the ecological dynamics of plant communities.