Anti-mite measures of aphids for protecting ants promote persistence of ant-aphid mutualism

Numerous studies focus on food-for-protection ant-aphid mutualism while ignoring the potential aphid’s protection for ants. To obtain a comprehensive understanding of bidirectional services in ant-aphid mutualism in goji berry, we manipulated the presence and abundance of ladybugs or mites, analyzing their impact on the ant-aphid mutualism persistence. We found that ants provided aphid protection from ladybugs and aphids provided anti-mite measures for protecting ants. For aphid protection by ants, 1) ant presence eroded the positive aphid-ladybug abundance relationship by reducing ladybug attendance. 2) Aphid-infested plants with more ants were less acceptable to ladybugs (ant-ladybug ratio above 1.75). 3) Ant presence impacted consumption traits of ladybugs, including aphid consumption (43.5% less), handling time (220.3% more), and theoretical maximum consumption (68.8% less). For ant protection by aphids, 4) aphid presence alleviated negative impacts on ants caused by mites by reducing mite abundance. 5) High-abundance mites (mite-ant ratio above 70) significantly reduced ant attendance. 6) The substantial volume of aphid honeydew had remarkable anti-mite effects by trapping mites (above 0.7 ml per leaf). Besides food-for-protection mutualism, our study indicates that anti-mite measures of aphids for protecting ants could promote the persistence of ant-aphid mutualism. Both protections were density-dependent, suggesting in practical applications of ladybugs, inundative biological control based on density advantage could be a promising option for rapid impact on aphids. Effective control strategies should focus on reducing the aphid abundance below the economic threshold rather than attempting eradication, allowing aphids to naturally suppress mite populations. This could effectively reduce the dosage of pesticide products.