& Key message Acacia longifolia and Acacia mearnsii exhibit different reproductive behavior (viability, germination, and dormancy) in relation to fire and seed maturation. The potential of invasion of A. longifolia is stronger than that of A. mearnsii. A. longifolia germinates abundantly between fires and after fires, while A. mearnsii only germinates after fire and needs higher thermal thresholds to break dormancy. & Context Fire affects environments through the modification of biological

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... sses such as seed viability, dormancy, and germination. Seed maturation stage can modulate seed response to fire. Invasive alien species could be enhanced by forest fires. & Aims To analyze the viability, germination, and dormancy of two invasive alien species (Acacia longifolia and Acacia mearnsii) in relation to fire and seed maturation. & Methods Viability of seeds was obtained performing a tetrazolium test. Additionally, we obtained germination and dormancy in mature and fresh seeds simulating fire conditions through different levels of fire factors (smoke, ash, charcoal, and heat). & Results Control viability of seeds was 100% in the two Acacia species and maturation stages and severe heat reduced it to zero. Germination of A. longifolia varied depending on the maturation stage, being higher in fresh seeds. In A. mearnsii, germination did not change with maturation. In both species, heat stimulated germination by breaking seed dormancy. Seed maturation stage and fire factors affect the germination speed of each species differently. & Conclusion Fire reduces viability, stimulates germination, and breaks dormancy of the two species. Seed maturity exerts notable effects on A. longifolia reproductive behavior.