Adaptive evolution of a generalist parasitoid: implications for the effectiveness of biological control agents

Abstract

The use of alternative hosts imposes divergent selection pressures on parasitoid populations. In response to selective pressures, these populations may follow different evolutionary trajectories. Divergent natural selection could promote local host adaptation in populations, translating into direct benefits for biological control, thereby increasing their effectiveness on the target host. Alternatively, adaptive phenotypic plasticity could be favored over local adaptation in temporal and spatially heterogeneous environments. We investigated the existence of local host adaptation in Aphidius ervi, an important biological control agent, by examining different traits related to infectivity (preference) and virulence (a proxy of parasitoid fitness) on different aphid-host species. The results showed significant differences in parasitoid infectivity on their natal host compared with the non-natal hosts. However, parasitoids showed a similar high fitness on both natal and non-natal hosts, thus supporting a lack of host adaptation in these introduced parasitoid populations. Our results highlight the role of phenotypic plasticity in fitness-related traits of parasitoids, enabling them to maximize fitness on alternative hosts. This could be used to increase the effectiveness of biological control. In addition, A. ervi females showed significant differences in infectivity and virulence across the tested host range, thus suggesting a possible host phylogeny effect for those traits.

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

“…In the case of Aphidius avenae, although a release was performed, this parasitoid has not been as successful as it is in the northern hemisphere. Zepeda-Paulo et al (2013) reported Aphidius avenae in Chile, and the present study confirms its presence via classical and molecular methods, adding it to the list of aphidiines that prevail in Chilean agroecosystems.…”

“…Cereal aphids constitute a large group of pest species that directly and indirectly affect the yield of cereals globally. A rich assemblage of parasitoids is co-occurring and potentially interacting in cereal systems in Chile (Zepeda-Paulo et al, 2013). Of all Aphidiinae present in Chile, the vast majority were introduced for biological control programs (Starý, 1995).…”

Temporal variability of aphid biological control in contrasting landscape contexts

“…Although classical biological control of cereal aphids in Chile has been carried out through the action of parasitoid wasps (Hymenoptera: mainly Aphidiidae) (Gerding et al, 1989;Starý et al, 1994;Zepeda-Paulo et al, 2013), the role of the predators may also be important, particularly in the early spring before the build-up of parasitoid populations. Coccinellid beetles are known to be important aphid predators in various agricultural systems (Frazier, 1988;Hodek and Honek, 1996;Obrycki et al, 2009), and native and introduced species are present in Chile, providing a substantial biological control service (Grez et al, 2004;Zaviezo et al, 2006).…”

Does sex‐biased dispersal account for the lack of geographic and host‐associated differentiation in introduced populations of an aphid parasitoid?

“…1993; Zepeda-Paulo et al. 2013). Populations of A. ervi in Chile show a similarly high virulence (with no fitness trade-offs) and host fidelity in parasitoid females on both S. avenae and A. pisum complex (alfalfa and pea host races) (Zepeda-Paulo et al.…”

“…2008; Zepeda-Paulo et al. 2013); conversely, little is known on the male preference for mating. Host fidelity has been implicated in the rapid experimental evolution of virulence (a proxy of parasitoid fitness) of A. ervi on novel hosts (Henry et al.…”