Publication details
Association between arthropod densities suggests dominance of top-down control of predator-prey food-webs on pear trees during winter
| Authors | |
|---|---|
| Year of publication | 2022 |
| Type | Article in Periodical |
| Magazine / Source | Food Webs |
| MU Faculty or unit | |
| Citation | |
| Web | https://doi.org/10.1016/j.fooweb.2022.e00261 |
| Doi | http://dx.doi.org/10.1016/j.fooweb.2022.e00261 |
| Keywords | Biocontrol; Ecosystem exploitation hypothesis; Food -web; IPM; Organic management; Winter activity |
| Description | Although winter in the temperate zone is considered to be the period of arthropod quiescence, some pests and their natural enemies remain active and interact in simplified food-webs. Limited information exists about the relative importance of top-down and bottom-up processes regulating arthropod food-webs and their spatio-temporal dynamics during winter. This information is essential for the development of effective conservation biocontrol methods. We investigated how the pest management of pear orchards (integrated [IPM] vs organic) and tree location within orchards (margin vs centre) influence the association between densities of winter-active spiders, insect herbivores and winter-inactive predators (spiders, insects) from October to April. We installed carboard bands on trunks and branches of pear trees in four organic and four IPM orchards to collect bark -dwelling arthropods. We then modelled relationships between the densities of four functional arthropod groups, namely winter-active spiders, winter-inactive spiders, winter-inactive insect predators, and herbivores. In early winter, we found a hump-shaped relationship between the densities of winter-active spiders and her-bivores. This agrees with the top-down model of the ecosystem exploitation hypothesis, predicting that predators are first bottom-up limited, then accumulate with prey densities, and exert top-down control when they become sufficiently abundant. The densities of herbivores strongly declined during winter, a phenomenon which may be partly, along with other causes of natural mortality, attributable to predation by winter active spiders. The as-sociation between winter-active spiders and winter-inactive arthropod predators switched from positive to none in organic orchards or even to a negative association in IPM orchards. Negative intraguild interactions seem to be intensified due to the declining availability of alternative prey. Overall, the investigated food-webs seem to be mostly top-down regulated during winter, and IPM seems to intensify intraguild interactions. |
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