Spatiotemporal variations in aphid‐parasitoid relative abundance patterns and food webs in agricultural ecosystems

Abstract

Abstract. Understanding the stability of communities is fundamental in theoretical and applied ecology.Organisms atop trophic chains are particularly sensitive to disturbance, especially when they are dependent on a specific trophic resource subject to strong fluctuations in density and quality, which is the case of parasitoids. We investigated the (1) variability in spatiotemporal relative abundance patterns of a cereal aphid parasitoid community, determining at what scales such patterns vary in agrosystems. We also investigated whether (2) parasitoid relative abundances are strongly influenced by host relative abundances and if (3) different host species are exploited at distinct rates. Aphid parasitoid populations were monitored in three remote agricultural regions in France between 2010 and 2012. Five parasitoid species (Hymenoptera: Braconidae: Aphidiinae) and three aphid species (Hemiptera: Aphididae) were identified in each of those three regions. Fields sampled in one region in a single year exhibited similar relative abundance patterns, with aphid parasitoid communities varying across regions and years. All parasitoid species were able to exploit each monitored host species. Metopolophium dirhodum Wlk was consistently a more frequent species among parasitized aphids than among living aphids, indicating that this aphid species was exploited at a higher rate than the other two aphid species found (Sitobion avenae F and Rhopalosiphum padi L). Those findings suggest the cereal aphid-parasitoid network is not strictly determined by the intrinsic permanent environmental characteristics but partially varies from one year to another. The similarity in abundance patterns in different fields of a region in a given year suggests the existence of a mechanism allowing a rapid synchronisation of the relative abundance patterns at an intraregional scale. This phenomenon could be useful in predicting host-parasitoid communities and bear important consequences for the ecosystem service provided by parasitoids.

The effect of landscape complexity and microclimate on the thermal tolerance of a pest insect

“…The general decline in dominance of R. padi from winter to spring, with a concurrent increase to dominance of S. avenae by spring is a commonly observed pattern in the population composition of cereal aphids (Andrade et al ., , ; Alford et al ., ). In this study, during winter sampling, R. padi and M. dirhodum were present in all sampled fields and S. avenae in 2 of the 5 sampled fields.…”

Seasonal variations of host resources influence foraging strategy in parasitoids

“…In spring, A. rhopalosiphi remains numerous, but A. matricariae is not frequently found in cereal crops; other species, such as Aphidius avenae Haliday and Aphidius ervi Haliday, become more frequent (Krespi, 1990;Krespi et al, 1997;Andrade et al, 2013Andrade et al, , 2015. In winter, Aphidius matricariae Haliday and Aphidius rhopalosiphi De Stefani-Perez (Hymenoptera: Braconidae, Aphidiinae) are the dominant species in the guild.…”

“…Aphid and parasitoid densities are low in winter, but parasitism rate can reach 38% (Andrade et al, 2013). During spring, the density of aphids increases rapidly, and parasitism rates decrease accordingly (Andrade et al, 2015).…”

Abundancia y prevalencia de Aphidius avenae (Hymenoptera: Braconidae: Aphidiinae) en Chile

“…There may be other factors that could influence the prevalence of A. avenae. For instance, there are differences in prevalence of A. avenae among western European populations, which could respond to intraregional variations (Andrade et al 2015); however, the factors that explain this variation of A. avenae in Europe has not been addressed. Another factor, such as the effect of facultative protective endosymbionts, is not clear for this species, microbial endosymbionts in Chilean populations of S. avenae could select against A. avenae.…”