Abiotic conditions modify the trophic structure in the predator-prey avocado mite community

Abstract: The well-functioning of arthropod communities providing important ecological services, such as biological pest control, might be jeopardised by changes in biotic interactions caused by shifts in abiotic conditions, which are predicted in models of climate change. In this study, we examined the role of abiotic conditions in shaping the trophic structure in a predator-prey mite community present in avocado orchards in South-eastern Spain, in the presence or absence of alternative food, i.e. pollen. In coastal areas, with relatively mild abiotic conditions, the community is mainly composed of the herbivore pest Oligonychus perseae Tuttle, Baker & Abatiello (Acari: Tetranychidae) and two species of phytoseiid mites: Neoseiulus californicus McGregor and Euseius stipulatus Athias-Henriot (Mesostigmata: Phytoseiidae). We carried out laboratory experiments where interactions between species were evaluated at the individual level, and at two abiotic conditions: “mild” and “hot and dry”. At mild conditions, our results showed that the structure of the community resembles a 4-level trophic chain, with E. stipulatus females preying preferentially on juveniles of N. californicus, and juveniles of E. stipulatus hampering females of N. californicus from preying on the pest. At hot and dry conditions, the structure of the community shifted into one with both predator species competing for the pest. When alternative food (pollen) was supplied, trophic interactions between predators were reduced since E. stipulatus fed exclusively on pollen, what strengthened the predator-prey interaction between N. californicus and the pest, at both abiotic conditions. Our results evidenced that predatory interactions among the components of the community were strongly affected by abiotic conditions, resulting in community configurations that often favoured herbivory.Extended abstract