Gall initiation enhances the availability of food resources for herbivorous insects

Abstract

Summary1. Insect herbivory may have not only negative but also positive plant-mediated effects on other insect herbivores. We investigated plant-mediated effects of the stem gall midge Rabdophaga rigidae on other insect herbivores through regrowth response of the willow Salix eriocarpa. 2. Gall initiation on current-year shoots stimulated the development of lateral shoots, followed by a secondary leaf flush. Lateral shoots and upper leaves on galled shoots were less tough and had a higher water and nitrogen content. 3. Colonization rates by the aphid Aphis farinosa were significantly higher on galled shoots than on ungalled shoots, because this aphid frequently colonized lateral shoots. 4. Adults of two leaf beetles, Plagiodera versicolora and Smaragdina semiaurantiaca , were more abundant on galled than on ungalled shoots; they preferentially fed on young leaves produced during the secondary leaf flush. 5. Gall initiation positively affected aphids and leaf beetles by enhancing the availability of food resources as a result of the regrowth responses of S. eriocarpa . This indicates that the regrowth responses of plants to insect herbivory provide an important mechanism responsible for positive effects on other insect herbivores.

The effects of foliar pubescence and nutrient enrichment on arthropod communities ofMetrosideros polymorpha(Myrtaceae)

“…obs.). On Salix, insect stem galls increased the growth of lateral shoots, which were then less tough and had higher nitrogen and water contents (Nakamura et al, 2003). In addition to increased food resources, evacuated galls provide structural heterogeneity on Metrosideros, and Collembola and Psocoptera were observed foraging or residing within excavated gall tissues on leaves or stems.…”

“…The supply of limited nutrient resources is of fundamental importance to plant productivity and to the arthropod populations and communities on plants (White, 1984;Waring & Cobb, 1992;Kyto¨et al, 1996). Ambient plant nitrogen levels are low in comparison to consumer requirements (Mattson, 1980;White, 1984;Hartley & Crawley, 1997), and a wide variety of herbivore taxa feed preferentially on nitrogen-enriched tissues (Ball et al, 2000;Nakamura et al, 2003;Albrectsen et al, 2004). The abundance, biomass, and diversity of herbivores or detritivores and their predators often increase in fertilisation experiments in natural systems (e.g.…”

Evolutionary community ecology of plant‐associated arthropods in terrestrial ecosystems

“…A herbivore-removal experiment in the field and a herbivore-inoculation experiment in the greenhouse showed that herbivore community composition determined the degree of herbivore-induced regrowth of the local willow populations in the field. Herbivore-induced regrowth involved phenological changes in new leaf production, where the period of new leaf production expanded dramatically (Nakamura et al 2003;Utsumi et al 2009aUtsumi et al , 2013. Where new leaves are seasonally abundant due to strong willow regrowth, populations of the specialist leaf beetle (P. versicolora) develop exclusive preference for new leaves.…”

Indirect interactions in the microbial world: specificities and similarities to plant–insect systems

“…In terrestrial systems, herbivory by insects often induces trait changes in plant tissues, which indirectly affect the growth or abundance of other consumers of the same individual plants. These indirect effects can be negative, as a result of induced resistance to herbivory (e.g., Faeth 1986;Karban and Myers 1989), but can also be positive as a result of compensatory regrowth of plant tissue (e.g., Nakamura et al 2003) or of induced resistance that is effective against a certain consumer species yet actually benefits other consumers (Martinsen et al 1998). Although there are apparently many differences, we looked for functional similarities between TMIIs in aquatic microbial systems and those in terrestrial plantinsect systems.…”

“…Herbivory by this arthropod can induce trait changes of leaves within the same individual plant that has not actually been subjected to herbivory, known as induced systemic resistance (e.g., Agrawal et al 1999; see also Orians 2005 for review). Insects consuming the stem tissue can also induce a change in the availability of different types of resource, e.g., leaves, and thus affect other types of consumers (Nakamura et al 2003). In a broader sense, each leaf or each module (e.g., shoot) within an individual plant can be viewed as corresponding to an individual or clonal subgroup within the bacterial assemblage and different types of resources within a given individual plant (e.g., leaves, stems, and roots) as corresponding to distinct clonal subgroups in bacterial assemblages.…”