Abstract
Integrating elements from life tables into population models within a matrix framework has been an underutilized method of describing host–parasitoid population dynamics. This type of modeling is useful in describing demographically-structured populations and in identifying points in the host developmental timeline susceptible to parasitic attack. We apply this approach to investigate the effect of parasitism by the Asian parasitoid Aphelinus certus on its host, the soybean aphid (Aphis glycines). We present a matrix population model with coupled equations that are analogous to a Nicholson–Bailey model. To parameterize the model, we conducted several bioassays outlining host and parasitoid life history and supplemented these studies with data obtained from the literature. Analysis of the model suggests that, at a parasitism rate of 0.21 d−1, A. certus is capable of maintaining aphid densities below economically damaging levels in 31.0% of simulations. Several parameters—parasitoid lifespan, colonization timeline, host developmental stage, and mean daily temperature—were also shown to markedly influence the overall dynamics of the system. These results suggest that A. certus might provide a valuable service in agroecosystems by suppressing soybean aphid populations at relatively low levels of parasitism. Our results also support the use of A. certus within a dynamic action threshold framework in order to maximize the value of biological control in pest management programs.
Highlights
The ways in which demography, life history, interspecific interactions, and the biotic or abiotic characteristics of a habitat affect the dynamics of consumer–resource interactions may be investigated through simple experiments and ecological models [1]
The fully parameterized matrix model predicted that Aphelinus certus reduces soybean aphid populations below the economic threshold in 9.9% of simulations and
Host suppression was predicted at a parasitism rate of 0.21 d−1, which corresponds with 3.4% of the aphid population being visibly mummified; notably, because parasitism was dynamic, relatively low parasitism rates early in the season could still be associated with low peak host densities
Summary
The ways in which demography, life history, interspecific interactions, and the biotic or abiotic characteristics of a habitat affect the dynamics of consumer–resource interactions may be investigated through simple experiments and ecological models [1]. Population modeling has often been used to quantify the importance of parasitoids as natural enemies within a broad range of ecological and evolutionary processes [4]. Other approaches, such as life table analyses, provide valuable insight into the effect of mortality imposed by parasitoids and other natural enemies on host populations [5, 6].
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