Multiple infestation by seed predators: the effect of loculate fruits on intraspecific insect larval competition (original) (raw)

2001, Acta Oecologica-international Journal of Ecology

Many morphological features of fruits are important factors affecting predispersal seed predation by insects. This paper analyses the predispersal seed predation process of a major predator (a Noctuidae lepidopteran larvae) in loculate fruits of a bushy perennial plant, Cistus ladanifer. The main aim of the study is to assess the potential effect of internal valvae (which partition groups of seeds) in the intraspecific competition between larvae in multiple-infested fruits. Our results show that larvae do not reject already infested fruits, but they avoid the proximity of other larvae within the fruit, keeping an average minimum distance of one locule. In multiple-infested fruits, larval mortality increases and the proportion of seeds consumed by each larvae decreases. In those situations in which valvae keep apart larvae within a fruit, these only suffer the cost of exploitation competition with a low acquisition of resources. However, when all valvae between them are pierced by the larvae, competition switches to an interference component and larval mortality increases markedly. The existence of valvae within a fruit allows larvae to diminish the cost of intraspecific competition, obtaining high life expectancies (70%), even in triple-infested fruits. © 2001 Éditions scientifiques et médicales Elsevier SAS Cistus ladanifer / intraspecific competition / loculate fruits / seed predation *Correspondance and reprints: Fax: +34 1 3945081.

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