Summary1. Mycorrhizal symbiosis is thought to affect interactions between plants and herbivores by its influence on plant growth, nutrition and the plants defence system. Moreover, arbuscular mycorrhizal fungi (AMF) may enhance the inducibility of resistance responses. Until now, induction of plant resistance has not been considered to be a mechanism affecting the outcome of mycorrhization for plant-herbivore interactions. 2. Here, we test the hypothesis that the resistance of plants against herbivores depends on the induction of plant resistance by previous herbivory and mycorrhization. With a full factorial experiment in a greenhouse, we examined responses in growth of seven herbaceous plant species to AMF and the induction of resistance. To evaluate whether induced resistance is higher in plants with AMF we analyzed the combined effects of AMF and induction on herbivory, using bioassay caterpillars (Spodoptera littoralis). 3. Across all species, mycorrhization increased growth of plants and performance of the bioassay herbivore feeding on them. If, however, we induced resistance by allowing a caterpillar to feed for a short period on the plants, mycorrhization did not increase plant growth and performance of a subsequent herbivore that fed on the plant. This suggests that the increased plant resistance after induction was dependent on the symbioses with AMF. 4. Our results indicate that induction interacts with the allocation of the additional resources provided by mycorrhization towards plant growth and plant resistance. Therefore, mycorrhiza may play an important but hitherto overlooked role in the induction of plant resistance against herbivores.

Morphological traits provide the interface between species and their environment. For example, body size affects the fitness of individuals in various ways. Yet especially for ectotherms, the applicability of general rules of interspecific clines of body size and even more so of other morphological traits is still under debate. Here we tested relationships between elevation (as a proxy for temperature) and productivity with four ecologically relevant morphological traits of orthopteran assemblages that are related to fecundity (body size), dispersal (wing length), jumping ability (hind femur length), and predator detection (eye size). We measured traits of 160 orthopteran species that were sampled along an extensive environmental gradient at Mt. Kilimanjaro (Tanzania), spanning elevations from 790 to 4,410 m above sea level (a.s.l.) with different levels of plant productivity. For traits other than body size, we calculated the residuals from a regression on body length to estimate the variation of traits irrespective of body size. Bayesian analyses revealed that mean body size of assemblages, as well as the means of relative wing length, hind femur length, and eye size, decreased with increasing elevation. Body size and relative eye size also decreased with increasing productivity. Both phylogenetic relationships, as well as species-specific adaptations, contributed to these patterns. Our results suggest that orthopteran assemblages had higher fecundity and better dispersal and escape abilities, as well as better predator detection at higher temperatures (low elevations) than at low temperatures (high elevations). Large body sizes might be advantageous in habitats with low productivity because of a reduced risk of starvation. Likewise, large eye size might be advantageous because of the ability to detect predators in habitats with low vegetation cover, where hiding possibilities are scarce. Our study highlights that changes in temperature and productivity not only lead to interspecific changes in body size but are also related to independent changes of other morphological traits that influence the ecological fit of organisms in their environment.