A herbivoria por insetos sugadores influência a colonização por heteroespecíficos e coespecíficos?

Abstract

Plants are subject to attack by herbivores throughout their life cycle, as a result of this pressure, several defense mechanisms have emerged in plants to deal with the attack of these organisms. On the other hand, as a result of the pressure of the host plants' defenses, herbivores' strategies emerged that allowed them to overcome them and, thus, feed themselves. One of the mechanisms is the manipulation of defenses induced by the activation of the salicylic acid (SA) pathway, a plant hormone that can antagonistically interact with jasmonic acid (JA), an important signal of induced defenses against herbivores. Many sucking herbivores feed on the corn plant (Zea mays L.), such as the corn aphid, Rhopalosiphum maidis (Fitch) (Hemiptera: Aphididae) and the corn leafhopper Dalbulus maidis (DeLong & Wolcott) (Hemiptera: Cicadellidae). In this context, the present work aimed to investigate whether herbivory by aphids or leafhoppers increases the attractiveness of the plant and facilitates the establishment of heterospecific and conspecific individuals. Assays of host preference, performance and oviposition preference were carried out with maize plants infested with D. maidis, or R. maidis, and plants not infested. The host preference was observed in a double-choice test by counting aphids and leafhoppers over time, the performance of aphids, measured in terms of number of individuals in the colony, and of leafhoppers, in terms of survival and development and the oviposition preference of the corn leafhopper was evaluated in double-choice tests, in plants infested by conspecifics, heterospecifics and not infested. In the host preference tests of R. maidis and D. maidis, greater host preference was observed for infested plants, compared to non-infested plants over time. However, when plants infested by conspecifics or heterospecifics were contrasted, the corn aphid had a greater preference for plants infested by heterospecifics, while D. maidis had no preference among infested plants. For the corn leafhopper oviposition preference test, females of D. maidis laid a higher number of eggs on plants previously infested by conspecific or heterospecific insects, compared to non-infested plants. However, when plants infested by conspecifics or heterospecifics were contrasted, there was a greater preference for plants previously infested by conspecific insects. As for the performance test of D. maidis, the development time from egg to adult was shorter in plants infested by conspecifics than heterospecifics and uninfested plants, indicating a better host quality of plants previously infested by conspecifics. Regarding the performance of R. maidis, colony size was higher in plants infested by heterospecifics or conspecifics than in uninfested plants. However, when comparing the performance of R. maidis in plants infested with conspecifics and heterospecifics, there was better performance of the aphid in plants infested with heterospecifics. Thus, the results indicate that there is an influence on the colonization of insects by heterospecifics and conspecifics in the choice of these insects and that, probably, these sucking insects suppress the defenses of the corn plant.