1. Intraspecific variability in herbivore response to elemental defences is caused by the metal itself
- Author
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Godinho, Diogo, Branquinho, Cristina, Magalhães, sara, and Repositório da Universidade de Lisboa
- Subjects
Ecology ,Insect Science ,fungi ,food and beverages ,Plant Science ,Agronomy and Crop Science ,Ecology, Evolution, Behavior and Systematics - Abstract
Some plants are able to accumulate on their leaves metals taken from the soil, using this as a defence against herbivorous arthropods. However, herbivore response to metal accumulation in plants is known to be variable. While some species and taxonomic groups are less affected than others, hormetic effects have also been observed in spider-mites, herbivorous crop pests. Still, knowledge on the range and causes of intraspecific variation in the response of herbivores to metal accumulation is lacking. Here, using two species of spider-mites, Tetranychus urticae and T. evansi , we tested the variation of 17 populations in response to cadmium-accumulating tomato plants and the drivers of such variation. We observed a non-linear, hormetic response of mites to plants with cadmium in some, but not all, populations. The same pattern was recaptured in artificial diets with different concentrations of cadmium but not in artificial diets with sugars, which change in the plant in response to cadmium. This indicates that herbivores on metal-accumulating plants respond to metals, not to the variations in leaf carbohydrates. Therefore, metals exert different effects on herbivores according to the amount accumulated, but independently of other plant traits. This knowledge is key to the understanding of the mechanisms underlying herbivore responses to metal-based plant defences and to pesticides containing heavy metals. Additionally, our findings draw attention to the need of considering intraspecific variation and non-linearities when studying the effects of metals and other contaminants on herbivorous arthropods.
- Published
- 2022