Birds and ants can favour the germination of an endemic Neotropical magnolia

Background: Seed dispersal, a fundamental process influencing the distribution and survival of most flowering plants, is key to the understanding of the ecology of tree species and forest restoration potential. However, little is known about the seed dispersal and germination of magnolias, especially in the Neotropics. Aims: To elucidate the effect of the removal of the sarcotesta (red outer seed coat) of seeds by birds and ants on the germination of Magnolia vovidesii, a species endemic to Mexico. Methods: We recorded birds consuming M. vovidesii seeds using motion-activated camera traps and focal observations for 36 days. In order to understand how birds and ants removed sarcotesta and how this was related to its germination, we made two independent experiments, one using three captive clay-coloured thrushes, and another one using ants in the field. Results: We recorded nine species of birds that fed on magnolia seeds. The clay-coloured thrush, an important consumer of these seeds, eats and subsequently regurgitates, magnolia seeds without sarcotesta. We found that seeds whose sarcotesta had been removed by birds and ants had a significantly higher germination than those with sarcotesta (p < 0.0005). Conclusions: Without the removal of the sarcotesta, magnolia seeds do not germinate at all. Our work demonstrates that birds and ants have a key role in preserving populations of magnolias.