Predação de sementes em Erythrina falcata Benth. Fabaceae - Faboideae: Biologia dos insetos predadores e estratégias de compensação da planta

Abstract

Seed production is an important stage in the life history of plants, because these are the structures responsible for the replacement of individuals and also the expansion and perpetuation of the population, while also acting as a dispersion medium for colonization of distant areas of a population. The Seed predation exerted by insects has negative effects on plant reproduction by limit the supply of seeds and prevents germination. Erythrina falcata, known as corticeira ou bico-de-papagaio is a native plant from Atlantic forest, pioneer mainly for planting trees in urban environments and the restoration of degraded forests. In this work were identified the species of insects that prey on seeds of E.falcata in pre-dispersion and ecological aspects of interaction between this insects and plant. Five insect species were found preying on seeds of E. falcata, three of which belong to the order Lepidoptera, Crambidae family, (Agathodes designalis, Liopasia ochracealis and Terastia meticulosalis) and two coleopterans (Cathartus quadricollis - Silvanidae and Paratenetus sp - Tenebrionidae). Was observed also one species of hymenopteran (Macrocentrus sp. - Braconidae) which is parasitoid of larvae of lepidopterans. The species have different behaviors of predation, larvae of lepidopterans feeding only on green seeds and the coleopterans only of mature seeds with the endosperm accessible. This makes coleopterans secondary predators, dependent on the primary action of the larvae of lepidopterans. The three species of lepidopterans feed more than one seed during its larval stage, increasing the predation impact. The presence of the parasitoid Macrocentrus sp. can have effect on rates of predation because parasitized larvae do not feed and pupate, being the parasitoid completes its development inside the host pupa, killing her and then emerging. Plant biometric variables such as pod length and width, are related to the number of seeds per pod. This condition, however, not has influences on predation rates in the sampled area. The seed predation ranged from minimum of the 50% to a maximum of the 83% of the seeds between the plants sampled, whereas average overall predation was 70% of viable seeds. This demonstrates that the plant may have shaped its natural history in the presence of insect predators which enables his stay in the environment, indifferent to predation, or has strategies that seek to reduce the impact of predation on their seeds. Among these strategies, is possible that plants have periods of masting fruits, followed by intervals without production of fruits and seeds. This phenomenon generates unpredictability of resources for seed predators, regulating and reducing their population levels and has direct effects on rates of seed predation.