Effect of Plant Defenses and Plant Nutrients on the Performance of Specialist and Generalist Herbivores of Datura: A Macroevolutionary Study

Macroevolutionary patterns in the association between plant species and their herbivores result from ecological divergence promoted by, among other factors, plants' defenses and nutritional quality, and herbivore adaptations. Here, we assessed the performance of the herbivores Lema trilineata daturaphila, a trophic specialist on Datura, and Spodoptera frugiperda, a polyphagous pest herbivore, when fed with species of Datura. We used comparative phylogenetics and multivariate methods to examine the effects of Datura species' tropane alkaloids, leaf trichomes, and plant macronutrients on the two herbivores & PRIME; performances (amount of food consumed, number of damaged leaves, larval biomass increment, and larval growth efficiency). The results indicate that species of Datura do vary in their general suitability as food host for the two herbivores. Overall, the specialist performs better than the generalist herbivore across Datura species, and performance of both herbivores is associated with suites of plant defenses and nutrient characteristics. Leaf trichomes and major alkaloids of the Datura species are strongly related to herbivores' food consumption and biomass increase. Although hyoscyamine better predicts the key components of the performance of the specialist herbivore, scopolamine better predicts the performance of the generalist; however, only leaf trichomes are implicated in most performance components of the two herbivores. Nutrient quality more widely predicts the performance of the generalist herbivore. The contrasting effects of plant traits and the performances of herbivores could be related to adaptive differences to cope with plant toxins and achieve nutrient balance and evolutionary trade-offs and synergisms between plant traits to deal with a diverse community of herbivores.

Automated summary

Macroevolutionary patterns in the association between plant species and their herbivores are influenced by ecological divergence driven by plant defenses, nutritional quality, and herbivore adaptations. This study examined the performance of two herbivores, Lema trilineata daturaphila, a specialist on Datura, and Spodoptera frugiperda, a generalist pest, when fed with different species of Datura. The results showed that Datura species varied in their suitability as food host for the two herbivores, with the specialist performing better overall. The herbivores' performance was associated with plant defenses, such as leaf trichomes and tropane alkaloids, as well as nutrient characteristics.