Tomato spotted wilt virus facilitates non-vector spider mite species (Tetranychus urticae and Tetranychus evansi) on whole tomato plants

Abstract Coinfections where hosts harbour more than one parasite species are common in nature. Facilitation among parasites enabling them to better exploit host resources is widespread with direct consequences for their life-history. Plant viruses can facilitate their vectors which may increase their transmission, but which can also have positive effects on non-vector species that share the host plant. Here we study facilitation of two (non-vector) species of Tetranychus spider mites, Tetranychus urticae and T. evansi , by a plant virus, tomato spotted wilt virus (TSWV), in coinfections on a host tomato plant, Solanum lycopersicum . We compared the effect of different strains of TSWV on life-history traits of Tetranychus mites on both cut leaves and whole plants of different tomato varieties. TSWV facilitated both species of spider mites on two different tomato varieties on whole plants, with more offspring of both species becoming adults. In contrast, on cut leaves, facilitation of T. urticae was much more variable depending on the viral strain and tomato variety. We attribute this to the non-homogeneous spread of virus throughout the host plant, which may limit the potential for facilitation if it is plant mediated, either via the host immune response or resource based. Our experiments demonstrate that facilitation among parasites can shape life-history traits of non-vector species which may have knock-on effects driving epidemics of plant parasites and pests.