Comparing resource exploitation and allocation of two closely related aphid parasitoids sharing the same host

Abstract

International audienceSpecies belonging to the same guild (i.e. sharing the same resources) can reduce the negative effects of resource competition through niche partitioning. Coexisting species may differ in their resource exploitation and in the associated allocation of nutrients, depending on their resource niche. Trade-offs in nutrient allocation, such as between reproduction and survival, or between early and late reproduction, are moderated by the abundance and distribution of resources. In this study we investigate differences in larval resource exploitation and adult reproductive strategy of two sympatric aphid parasitoids sharing a common host. The habitat specialist Aphidius rhopalosiphi and the generalist Aphidius avenae occur in cereal crops of Western Europe, where both species attack the major host resource: the grain aphid Sitobion avenae. For this purpose, we measured their acquisition of capital lipid resources, their age-specific fecundity and reproductive effort, their life span and their metabolic rate. We found that these species do not differ neither in larval lipid accumulation nor in the number of eggs at emergence and the timing of egg production, but diverge in other adult reproductive strategies. The rate of adult egg production was higher in A. rhopalosiphi than A. avenae, but at the expense of producing smaller eggs. Throughout adult life, reproductive effort was higher in A. avenae, perhaps facilitated by its higher metabolic rate than A. rhopalosiphi. The divergence between species in life history syndromes likely reflects their adaptations to their resource niche. A high egg production probably allows the specialist A. rhopalosiphi to exploit more S. avenae individuals in cereal crops, while the generalist A. avenae because of its variety of hosts, maximizes the investment per egg but at the expense of a lower lifespan. Our results suggest that differential resource allocation may be a more common pattern that promotes coexistence of species within a guild

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

“…There is a scarce amount of information in the literature concerning competitive outcomes between the Aphidiinae species in this study, but our results show some indication that such interspecific interactions are not a major factor in determining relative abundance patterns. This can be due to resource partitioning, as Aphidiinae species have been known to exhibit distinct host resource exploitation strategies while exploiting the same host species, thus avoiding detrimental niche overlapping and allowing coexistence (van Baaren et al 2004, Le Lann et al 2012.…”

Multi‐scale and antagonist selection on life‐history traits in parasitoids: A community ecology perspective

“…In relation to longevity, it is possible that the energy reserve accumulated and/or the energy consumption rate would differ between parasitoids emerging from the two cereal aphid host species, S. avenae and M. dirhodum . The interspecific differences in energy consumption rates may be linked to differences in metabolic rates of adult parasitoids (Le Lann et al., ): both A. avenae and A. rhopalosiphi display contrasted metabolic rates and life spans but accumulate a similar amount of energy resources when exploiting S. avenae (Le Lann, Visser, van Baaren, van Alphen, & Ellers, ).…”

Intraspecific maternal competition induces summer diapause in insect parasitoids

“…Aphid mummies were taken from the parasitoid colonies, isolated in small gelatin capsules ( 5 mm), and acclimated to the experimental abiotic conditions until adult emergence (3-5 d). Following emergence, each parasitoid female was placed in the presence of 2 males for mating and provided a honey solution (70% dilution) for 36 h. This duration allows females to reach their maximum egg-load (Le Lann et al, 2012). Parasitoid females were then held along with aphids and honey in the experimental arenas for 48 h, following the 2 protocols described below.…”

“…These densities are encountered in the fields on wheat shoots (Roschewitz et al, 2005) and encompass the realized fecundities for 48 h of both parasitoid species. A. avenae and A. rhopalosiphi are able to produce about 62 and 31 mummies in 2 d, respectively (Le Lann et al, 2012). Naive mated females (i.e., without oviposition experience or contact with other females) were individually introduced into experimental arenas to parasitize aphids.…”