Caracterização e efeito de cascata trófica em uma rede multi-trófica: de fatores abióticos do solo a insetos associados a frutos

Abstract

This study has the following objectives: i) to describe the network of insects associated to the plant Senegalia tenuifolia (L.) Britton & Rose (Fabaceae: Mimosoideae) and their trophic relations and ii) to observe the occurrence of temporal and spatial variations on fruit and seed traits and in the abundance and interactions between their associated insect; iii) to verify the occurrence of trophic cascade effects over a network involving soil quality, fruit and seed traits and the abundance of their associated insects ; iv) to measure strength of the interaction intensity between organisms from different trophic levels of the network. Thereby, insects associated to S. tenuifolia fruits from eight subareas at the region of Lavras, MG, Brazil were evaluated. In each subarea, soil quality, fruit and seed morphological traits and their NPK constitution were evaluated. In addition, the abundance and intensity of the strength of the interaction between the species associated to the fruit were estimated. Thus, two Bruchinae and two Himenoptera seed-feeder species, seven Hymenoptera primary parasitoids, one secondary parasitoid and two presenting unknown relations with the studied network were observed. The subareas with a higher number of seeds also presented higher insect abundance. In regard to the temporal variation, the seeds were larger at the end of the reproductive season, as well as the abundance of insects. Regarding fruit and seed traits, a higher fruit and seed-feeders’ success on larger fruits and seeds and with higher NPK quantity in their constitution was observed. In general, a positive bottom-up trophic cascade effect, mediated by soil organic matter, was observed influencing the abundance of insects associated to S. tenuifolia fruit.