Mutualistic and antagonistic interactions involving mesquite seeds

CAMPOS, CLAUDIA MÓNICA; VELEZ, SILVINA; CAMPOS, VALERIA; GIANNONI, STELLA M.

Londres

Congreso; 11th International Congress of Ecology; 2013

British Ecological Society

Plant movement through seed dispersal provides the only means for most plants to colonize new habitats or escape competition, pathogens and herbivores associated with their mothers. Animals that consume fruits and seeds, and inadvertently disperse some seeds, are involved in the natural regeneration cycles of plant species, such as Prosopis flexuosa (Fabaceae) in the Monte desert of Argentina. The aim of this study is to summarize the role of mutualistic and antagonistic plant-animal interactions during predispersal and postdispersal stages of P. flexuosa life cycle. Animals participate in the seed dispersal cycle of P. flexuosa through propagule removal, fruit consumption, and handling, hoarding, ingestion, and deposition of seeds in faeces. Insect species of Apion and Scutobruchus consumed 5% of the seeds produced and they can act as partial or total predispersal seed predators. When seed predation is partial, germination is possible in 33% of the cases. Small rodents (e. g. Graomys griseoflavus, Akodon molinae, Calomys musculinus, Eligmodontia typus, and Microcavia asutralis) remove and hoard fruits and seeds and can act as predators or potential dispersers. Particularly, E. typus and M. australis were the species that transported more fruits and that could most improve seed germination because they scatterhoarded propagules and left seeds out of fruits. Non-native mammals (cow, horse, donkey, European hare, wild boar) and native mammals (Dolichotis patagonum, Pseudalopex griseus, Lama guanicoe) are endozoochorous dispersers. The passage through the digestive tract of mammals can affect the survival of insects parasitizing the seeds (e.g. in faeces of D. patagonum and P. griseus, 48% of bruchids were dead). The passage also modifies seed germination capacity and speed, with great variability depending on the particular mammal species. Subsequently, seedling establishment and sapling survival are related to defecation sites and to the activity of animals such as cattle. Small mammals and ants also remove seeds from cattle dung, and the importance of each removal group depends on season and on microhabitat characteristics. A wide range of animals act as dispersal agents of P. flexuosa using strategies that, although significantly affecting survival in some cases, can delay or speed germination. This is of great importance in deserts where climate conditions are unpredictable, and the seed must consequently wait for opportune moments.