Asymmetric Interaction between and on Sweet Orange Induced by Pre-Infestation.

Indirect interactions between herbivorous insects that share the same host have been focused on insects feeding on herbaceous plants, while few studies investigate similar interactions on woody plants. We investigated performance and feeding behavior of two citrus aphids, Patch and Kirkaldy, on sweet orange as affected by prior infestation of conspecifics and heterospecifics. Results showed that pre-infestation-induced interactions between and were asymmetric, with gaining more fitness. In detail, pre-infestation by decreased adult weight, enhanced survival rate and accelerated phloem sap acceptance of conspecifics. However, pre-infestation did not affect performance or feeding behavior of . In another infestation sequence, the pre-infestation of did not affect conspecifics, but positively affected heterospecifics, indicated as a decreased pre-reproductive period, enhanced survival rate, adult weight, fecundity, and feeding efficiency, i.e., faster access and acceptance of phloem sap, and longer phloem sap ingestion duration. Furthermore, we found pre-infestation enhanced amino acid concentration, amino acid to sugar ratio, activated salicylic acid and jasmonic acid marker gene expression, while pre-infestation only depressed jasmonic acid marker gene expression. Changes in nutrient and phytohormone-dependent defense probably underlie the asymmetric effect.