Predação e parasitismo em sementes de duas populações de Parkia platycephala Benth., em áreas de cerrado no nordeste do Brasil

Abstract

Two morphologically distinct populations of Parkia platycephala with different densities in the Cerrado, have their seeds preyed by larvae of the coleoptera Acanthoscelides imitator Kingsolver 1985, which are parasitized by the hymenoptera Stenocorse bruchivora Crawford 1900. In this study the effects of nesting, predation, and parasitism on seed germination were evaluated, and the rates of these events were compared between the two populations. Germination tests were conducted in laboratory, using four replicates of 50 seeds. Nesting, predation and parasitism rates for each population were estimated by sampling seeds from 20 fruits per individual, and from 15 individuals per population. The seeds of P. platycephala exhibit dormancy enforced by the seed coat. The nesting breaks the dormancy, and the pre-dispersal predation of seeds by the coleoptera larvae make them inviables. The larvae predation is biologically controlled by the hymenoptera parasitism. The seed predation rates for each population were 28% and 12%, respectively, being significantly higher in the white population, which produces more and smaller seeds per fruit than the other population. The highest predation occurs because of the highest nesting rate by the coleopterans, which is positively correlated with the number of seeds per fruit. The parasitism rate was 8%, approximately, and was not significantly different between the populations. The results indicate that the differences between the densities of these populations were not related to the biological interactions, as seed predation and parasitism.