Invasive plant indirectly regulates native plant decomposition by affecting invertebrate communities.
Invasive plants may have variable effects depending on their interactions with native species, yet few studies have examined the phenomenon of the invasive plant-mediated priming effect. To investigate the priming of invasive species on native leaf litter decomposition, we allocated two native leaf species of contrasting recalcitrance (Neosinocalamus affinis and Ficus virens) in single and double species mixtures with and without invasive Alternanthera philoxeroides, and then incubated them for 65 days in a eutrophic shallow lake. Invasive plant addition promoted decomposition of F. virens and a mixture of two native plants, with positive priming effects of 25.47% for F. virens and 30.49% for the mixture based on mass loss, respectively. However, the decomposition of N. affinis was inhibited, with a negative priming of -16.55%. In total, the associated faunal communities comprised 15 microinvertebrate taxa, 10 meioinvertebrate taxa, and 11 macroinvertebrate taxa. Among these, sarcodina (omnivores) were shared components colonizing all plant materials, while ciliates (filter-collectors) and cladocerans (filter-collectors) mostly colonized the mixture of native species and mixture × A. philoxeroides materials. The abundances of rotifers (filter-collectors) and chironomids (gather-collectors) were the highest in F. virens × A. philoxeroides materials. Compared to the faunal assemblage without A. philoxeroides treatments, the invertebrate richness and abundance, microalgae abundance and microbial respiration were more than one times higher with A. philoxeroides treatments. Our findings indicate that the priming effect can be induced by invasive A. philoxeroides, invertebrate community played an important role in this process.