摘要：The vegetation in north-eastern Patagonian steppe is characterized by two main functional groups: grasses and shrubs. The dynamics between these two groups has economic importance especially for livestock breeding. One of these shrubs is Fabiana imbricata, whose seeds are consumed by a hymenopteran insect that causes a reduction in its reproductive capacity. To evaluate this effect on seed production we sampled individuals in the steppe near the city of San Carlos de Bariloche (Río Negro). We measured parasitism frequency, seed number and seed weight in attacked and non-attacked capsules. Seed number in capsules attacked by the insect was lower than in the intact ones, but seeds were heavier. This increase in seed weight could have demographic meaning in some ecological scenarios, as seeds from attacked capsules could have some advantages for establishment.
