Effects of Self-Superparasitism and Temperature on Biological Traits of Two Neotropical Trichogramma (Hymenoptera: Trichogrammatidae) Species

Abstract

It is common for a female trichogrammatid to lay more than one egg per host, a phenomenon known as self-superparasitism, which exposes her offspring to intraspecific, intrinsic competition (IIC) with its own siblings. Information about how often self-superparasitism occurs and how IIC interacts with abiotic factors is rare, especially regarding the Neotropical Trichogramma species. Here we determined the frequency of self-superparasitism in Trichogramma atopovirilia Oatman & Platner (Ta) and T. pretiosum Riley (Tp), and the effects of IIC and temperature on the sex ratio, egg-to-adulthood period, and survivorship of both species' offspring. Individual females were offered eggs of Spodoptera frugiperda (J.E. Smith) for 30 min. A group of parasitized hosts was then dissected for determination of the self-superparasitism frequency, while another group was incubated at 15, 18, 21, 24, 27, 30, and 33°C. High rates of self-superparasitism were found in both Ta (0.55 ± 0.07) and Tp (0.62 ± 0.06). IIC interacted with temperature decreasing Ta and Tp's survivorship, lengthening the egg-to-adulthood period in Tp and shortening it in Ta, and balancing Ta's sex ratio. Based on survivorship rate, Ta and Tp could not be differentiated if their immatures develop in absence of IIC. However, in its presence, Tp was 3 × more likely to survive than Ta at 33°C, while at 15°C Ta survived 2× better than Tp. These results show that self-superparasitism can be very common in both Ta and Tp, and that its effects on the species' biological traits and competitiveness strongly depend on the IIC-temperature interaction.