Efeitos diretos e indiretos das interações de trofobiose entre hemípteros sugadores e formigas na reprodução de uma planta ornitófila

Abstract

Interactions among tending-ants, sap-sucking herbivores and their predators comprise multitrophic systems that may directly and indirectly affect host plant fitness. Sap-sucking herbivores interact antagonistically with the plants, directly by consuming the sap or indirectly when establish mutualistic relationships with ants, which may also drive costs for host plant reproduction if they repel pollinators. Given the possible variation in the ecological outcomes of these interactions, we simulate the presence of ants to inflorescences in order to access effects on pollinators behavior. In addition, we recorded the trophobionts and ants natural abundance in a population of the ornithophilous plant, Psittacanthus robustus (Loranthaceae). We also evaluated the consequences of variation in herbivore density on size of fruits and seeds produced, but also on seed germination and seedling establishment. The experiment controlling the presence of ants in the inflorescences did not show indirect effect on the behavior of the potential pollinator. However, dense aggregations of sap-sucking herbivores resulted in smaller seeds. The inoculation experiment also failed to highlight any direct effect on seed germination or seedling establishment. Our results show that the indirect effects does not affect host plant pollination and although the attack by the trophobiont herbivores resulted in direct negative effect. Nevertheless, these effects did not affect seed germination and establishment, showing that the host plants present mechanisms of herbivory tolerance. We highlight the importance of addressing direct and indirect effects on host plant fitness parameters to clarify the possible outcomes of interactions involving multitrophic systems