INTERACTIONS BETWEEN A HIGH-MOUNTAIN SHRUB, GENISTA VERSICOLOR (FABACEAE), AND ITS SEED PREDATORS

For three years we studied the interaction between Genista versicolor (Fabaceae) and three seed-predator species, one moth (Coleophora brunn eosignata; Coleophoridae) and two weevil species (Exapion compactum an d Exapion nov. sp.; Apionidae), to assess the impact of the insects on seed production and the reciprocal effect of the plant reproductive s trategies on the insect's survival. plants experienced three predisper sal mortality factors of ovules: early death of ovules, seed abortion and seed predation. Each fruit bore an average of 5.4 ovules, of which 4.0 ovules died early in their development and 0.1 aborted. Each frui t sets an average of 1.3 mature seeds. Seed predators invariably infes ted more than 65% of the fruits every year, killing 87% of the seeds r ipened by the plants. More than 90% of the seeds predators were weevil s. However, including the other two predispersal mortality factors, we found that the main lass was to ovule death (74% of the initial numbe r of ovules), whereas seed predation destroyed 19% of the ovules. The effect of the plant on the seed-predator survival is somewhat differen t. Although weevils were parasitized by a wasp, the main mortality fac tor during the larval stage within the fruits was starvation. Of weevi l larvae, 68% died before completing the life cycle because eggs were not laid on mature seed and were unable to enter a seed. As the plant capacity for filling seeds was not correlated with herbivory, the mort ality of weevil larvae depended mostly on external predispersal events .