Quantitative food webs of herbivore and related beneficial community in non-crop and crop habitats

Abstract

a b s t r a c tQuantitative food webs were constructed from the data collected, using visual observation technique, from May to July in 2005 and 2006 to describe separately the trophic relationships between the community of aphids and their natural enemies of predators and parasitoids in agricultural and semi-natural habitats in Gembloux, Belgium. In the web, a total of six aphid attacked by six parasitoid and 21 predator species were recorded in this study; 50 and 33 links between aphid and natural enemy species were respectively observed in 2005 and 2006. Aphid density varied seasonally and among years, and three species of aphid were particularly common in different habitats. The ratios of the number of aphid species to the number of species of either predators or parasitoids changed also seasonally. Most communities of insect herbivores are likely to be structured by apparent competition mediated by shared natural enemies more than to be structured by resource competition. The potential of two guilds of natural enemies to contribute in structuring aphid community through indirect interactions was assessed. The potential strengths of apparent competition between hosts mediated by parasitoids and predators were assessed using quantitative parasitoid/predator overlap diagrams. Symmetrical links were uncommon, and rare species were severely influenced by the presence of common aphids with which they shared parasitoids or predators or both. The study's results suggest that (i) stinging nettle aphids, acting as potential sources of apparent competition mediated by natural enemies, may be important in these highly connected communities and can control whole-community dynamics, and (ii) stinging nettle habitats, in providing an important alternative prey for natural enemies, are likely to play a key role in conservation biological control.Crown

Ecological specialization in Diaeretiella rapae (Hymenoptera: Braconidae: Aphidiinae) on aphid species from wild and cultivated plants

“…Cultivated habitats are abundant but temporary resources for phytophagous insects and their associated natural enemies, while uncultivated habitats can act as refuges for these organisms because they are more stable environments. These habitats provide alternative prey for predators or hosts for parasitoids (Alhmedi et al, 2011;Rusch et al, 2012). Many studies have demonstrated the importance of semi-natural habitats and their alternative resources in agroecosystems in determining the abundance and diversity of pest natural enemies (Tscharntke et al, 2007;Ricci et al, 2009Ricci et al, , 2011 and their efficiency for biological control (Langer & Hance, 2004).…”

Apparent competition leaves no detectable imprint on patterns of community composition: observations from a natural experiment

“…Importantly, few studies predicting a potential for apparent competition on the basis of quantitative food web structure (e.g. Müller et al , ; Lewis et al , ; van Veen et al , ; Hirao & Murakami, ; Alhmedi et al , ) have actually used experiments to verify the outcome in terms of realised dynamics (but see Morris et al , ; Tack et al , ). In the context of converting food web structure into concrete predictions on dynamics, the critical words of Robert Paine () still ring as urgently as they did when they were written 25 years ago: ‘I know of no one who, having assembled a data set on feeding relationships, considers those data to constitute much more than an incomplete preliminary description.’ Hence, a ‘focus on dynamic rather than static (= completely descriptive) properties [of food webs] would constitute a primary desideratum’ (Paine, , pp.…”

Peer Review #2 of "Multiple ecosystem services from field margin vegetation for ecological sustainability in agriculture: scientific evidence and knowledge gaps (v0.1)"

“…This is in agreement with the study by Bianchi & Werf (2004) who found the availability of non-pest aphids in the non-crop habitats leads to conservation of ladybirds for enhanced biological control. Thrips, aphids and stink bugs damage was reported to be reduced as a result of increased insect natural enemies in different field margin vegetation (Eyre et al, 2011;Alhmedi et al, 2011 andPease &Zalom, 2010 respectively). Other insect pests like moth larvae (Balzan & Moonen, 2014) and olive psyllids (Paredes et al, 2013) were also found to be effectively managed through enhanced biological control attributed to the non-crop vegetation diversity.…”