Conspecific and heterospecific interactions between two omnivorous predators on tomato

Antagonistic interactions among invertebrate predators such as intraguild predation and cannibalism have the potential to dampen top-down impacts on shared prey. Two abundant heteropteran predators, Macrolophus pygmaeus (Rambur) and Nesidiocoris tenuis Reuter co-occur in the tomato crops of the Mediterranean horticultural area where they both attack whiteflies and lepidoptera, the dominant herbivores in the crop. Experiments in the laboratory were used to assess the incidence of intraguild predation and cannibalism in these predators. The effects of these interactions on survivorship, progeny and within-plant distributions were studied, as well as the effect of the presence of M. pygmaeus on the damage caused by N. tenuis to tomato plants. When predators of different stages coexisted, only the mortality of M. pygmaeus second-third instar nymphs caused by N. tenuis adult females was observed. When predators of the same stage (second-third instar nymphs or adult females) coexisted, mortality caused by IGP and cannibalism was observed only between adult females and usually associated to the absence of additional prey. When adult females coexisted without additional prey, the progeny of both predator species were reduced, showing a relationship only with the density and not with the presence of other predator species. However, when additional prey was offered, only M. pygmaeus progeny were reduced, showing a higher capacity of N. tenuis to maintain their reproductive potential at high densities. When both predator species coexisted, N. tenuis adult females caused more damage to tomato plants, suggesting that their coexistence could affect the crop. The consequences of conspecific and heterospecific interactions of M. pygmaeus and N. tenuis are discussed for the biological control of whiteflies and other tomato pests.