Abstract
Herbivores contribute significantly to seed dispersal in both natural and agricultural systems through endozoochory, a process that can break seed physical dormancy (PY) in leguminous plants. However, the detailed mechanisms governing germination following seed ingestion and the combined effects of digestion and environmental conditions remain poorly understood, particularly in Mediterranean climates. This study examined the effect of sheep ingestion on PY break and germination potential in four pasture legume species critical for grassland sustainability. Seed from two species (Medicago polymorpha and Ornithopus sativus) were fed to sheep inside intact ligneous pods, another in a linear membranous pod (Biserrula pelecinus) and the last in membranous pods arranged in a capitulum (Trifolium hirtum), mimicking consumption in nature. Viable seeds recovered from faecal pellets and non-ingested (control) seeds were subsequently placed under natural soil conditions for 111 days, during which seed mass, moisture content, and PY status were periodically assessed. Seeds that had passed through the digestive tract showed significant increases in mass and moisture content after ingestion, indicating partial hydration post ingestion. The proportion of PY seeds decreased in all species after being placed on the soil surface, but the rate of dormancy loss varied among species. Seeds ingested within ligneous pods exhibited greater reductions in PY than membranous pods relative to their controls. These results suggest that digestive processes, coupled with environmental conditions after excretion, accelerate dormancy break, highlighting a complex interaction between biological and ecological factors in seedling regeneration. Our results provide important insights for managing pasture legumes in Mediterranean systems and highlight the need to consider herbivore-mediated seed dispersal in restoration and sustainable agriculture.