Ecology and Evolution J.; March 8, 2017; DOI: 10.1002/ece3.2848
Four genetically modified (GM) maize (Zea mays L.) hybrids (coleopteran resistant, coleopteran and lepidopteran resistant, lepidopteran resistant and herbicide tolerant, coleopteran and herbicide tolerant) and its non-GM control maize stands were tested to compare the functional diversity of arthropods and to determine whether genetic modifications alter the structure of arthropods food webs. A total number of 399,239 arthropod individuals were used for analyses. The trophic groups’ number and the links between them indicated that neither the higher magnitude of Bt toxins (included resistance against insect, and against both insects and glyphosate) nor the extra glyphosate treatment changed the structure of food webs. However, differences in the average trophic links/trophic groups were detected between GM and non-GM food webs for herbivore groups and plants. Also, differences in characteristic path lengths between GM and non-GM food webs for herbivores were observed. Food webs parameterized based on 2-year in-field assessments, and their properties can be considered a useful and simple tool to evaluate the effects of Bt toxins on non-target organisms.
Figure 1: (a, b) Food web in Coleoptera-resistant maize (Treatment 1) (a) and non-GM control maize (Treatment 903) (b), built by considering the abundance and interactions between trophic groups. The position and size of the circles intended to allow an easier way to identify functional groups. Figures are graphically adjusted by software (circles sizes) with abundances and were intended to allow an easier way to identify functional groups. Green circles, vegetation; orange circles, herbivores; red circles, predators; blue circle, parasitoids; yellow circle, parasitized neuropteran egg. S, number of trophic groups; L, number of links between trophic groups. Food webs were built with CoSBiLab software (Jordán et al., 2012). Weed species: Ech., Echinocloa crus-galli; Cyn., Cynodon dactylon; Sorg., Sorghum halapense; Conv., Convolvulus arvensis; Amar., Amaranthus retroflexus (the sixth weed species for entries 5, 8 and 903 was Rub., Rubus caesius). Herbivore group: Acar., Acaridae; Coll., Collembola; Aph., Aphididae; Auch., Auchenorrhyncha; Thys., Thysanoptera; Altic., Alticinae; Elat., Elateridae; Oul., Oulema melanopus; Thea, Thea vigintiduopunctata (powdery mildew consumer); Dipt., Diptera; Helic., Helicoverpa armigera; Predatory group: Stet. p., Stethorus punctillum (mite predator ladybeetle adult and larvae); Cocc., Coccinellidae (all polyphagous species); Neura., Neuroptera adult; Neurl., Neuroptera larvae; Aeol., Aeolothripidae; Carab., Carabidae; Staph., Staphylinidae; Nabis, Nabis spp.; Ori. , Orius spp.; Asil., Asilidae (adults and larvae); Syrph., Syrphidae; Aran., Araneae; Par., Parasitoids; Par. ne., Parasitized neuropteran egg