Pre-dispersal seed predation decreases plant progeny performance: the role of seed position within the fruit.

Abstract

Background and aims: Pre-dispersal seed predation is a critical interaction that may significantly affect species fitness. Most studies have addressed this question by focusing on seed size, while the effect of seed position within the fruit remains unexplored. We tested how seed position within fruits affects pre-dispersal seed predation likelihood and progeny performance in two dominant trees, Vachellia aroma and Gleditsia triacanthos (Fabaceae), that are causing encroachment and invasions in Argentina's Chaco Forest.

Methods: We quantified pre-dispersal seed predation by bruchid beetles across different seed positions (basal, middle, stylar) within fruits. Seed germination and seedling vigour and survival were compared among seeds from such positions.

Key results: Pre-dispersal seed predation was highest among seeds from the basal position in both species. In the absence of predators, basal seeds had higher survival and produced more vigorous seedlings than those from the middle and stylar positions.

Conclusions: Pre-dispersal seed predation not only reduced the quantity of seeds but also disproportionately negatively affected plant progeny performance. This selective predation may decrease seedling recruitment and thus impact population dynamics in both species. Our findings suggest that selective seed predation on seeds that would give rise to the most vigorous progeny may help regulate ecological processes such as invasion dynamics, while potentially promoting biodiversity.