Intraguild predation and cannibalism between Eriopis connexa and Cycloneda sanguinea (Coleoptera: Coccinellidae): potential effect on predators coexistence.

ROCCA, MARGARITA; RIZZO, ESTEFANÍA; SÁNCHEZ, NORMA; GRECO, NANCY

Málaga

Congreso; 4th International Entomophagous Insects Conference.; 2015

IEIC

The intraguild predation (IGP) could be considered as interspecific competition by interference, whereas the cannibalism (CANN) implies intraspecific competition. According to the theory, either species can exclude the other if interspecific competition is stronger than intraspecific competition. In contrast, coexistence is possible if intraspecific competition exerts the strongest effect on population growth of both species. The coccinellids Eriopis connexa (Ec) and Cycloneda sanguinea (Cs) feed on aphids and are present in the pepper crop in La Plata, Argentina. In a previous work we observed that the cannibalism of both species was high and E. connexa was the strongest intraguild predator. Our hypothesis is that Ec and Cs coexist in pepper crops because the cannibalism of Cs is higher than the IGP by Ec, even in presence of prey. We compared the CANN on eggs, L2 and L4 of Cs and the IGP by adults of Ec on eggs, L2 and L4 of Cs with and without aphids. In absence of prey, the intensity of CANN and IGP on eggs was high and similar (P= 0.69), whereas in presence of aphids IGP was higher than CANN (P˂ 0.001). The CANN on larvae was lower than the IGP both with and without prey (P< 0.001). For Cs the interspecific predation caused by Ec always was higher than the CANN, in absence and presence of prey, so it could be excluded from the system. The coexistence of these species can then explained by the differentially use of plant resources in space, such as oviposition sites, strata or structures of plants as refuge, and/or over time. Coexistence also could be possible if Cs can have a superior ability for resource exploitation, which would provide a competitive advantage over Ec, the strongest intraguild predator.