Abstract
Plant guttation is a fluid from xylem and phloem sap secreted at the margins of leaves from many plant species. All previous studies have considered guttation as a water source for insects. Here, we hypothesized that plant guttation serves as a reliable and nutrient-rich food source for insects with effects on their communities. Using highbush blueberries as a study system, we demonstrate that guttation droplets contain carbohydrates and proteins. Insects from three feeding lifestyles, a herbivore, a parasitic wasp and a predator, increased their longevity and fecundity when fed on these guttation droplets compared to those fed on control water. Our results also show that guttation droplets, unlike nectar, are present on leaves during the entire growing season and are visited by numerous insects of different orders. In exclusion-field experiments, the presence of guttation modified the insect community by increasing the number of predators and parasitic wasps that visited the plants. Overall, our results demonstrate that plant guttation is highly reliable, compared to other plant-derived food sources such as nectar, and that it increases the communities and fitness of insects. Therefore, guttation represents an important plant trait with profound implications on multi-trophic insect–plant interactions.
Highlights
Plants possess multiple characteristics that affect their interactions with mutualistic and antagonistic organisms [1,2], such as the plants’ interactions with herbivores and the natural enemies of herbivores [3,4,5,6,7]
To evaluate the effect of guttation on D. suzukii, A. ervi and C. rufilabris fecundity, approximately 75 individuals (2 : 1 female : male) of each insect species were placed inside a transparent, cylindrical polypropylene plastic cup (946 ml; diameter, 114 mm; height, 127 mm; Paper Mart, CA, USA) and were provided one of the five diets described above for 24 h to ensure mating
The longevity of adult females and males of D. suzukii, A. ervi and C. rufilabris was higher when they fed on guttation as a food source than on the sugar plus protein, protein-only or water-only diets but was similar to those that fed on a sugar-only diet
Summary
Plants possess multiple characteristics that affect their interactions with mutualistic and antagonistic organisms [1,2], such as the plants’ interactions with herbivores and the natural enemies of herbivores [3,4,5,6,7]. To evaluate the effect of guttation on D. suzukii, A. ervi and C. rufilabris fecundity, approximately 75 individuals (2 : 1 female : male) of each insect species were placed inside a transparent, cylindrical polypropylene plastic cup (946 ml; diameter, 114 mm; height, 127 mm; Paper Mart, CA, USA) and were provided one of the five diets (ad libitum) described above for 24 h to ensure mating. To determine the effects of abiotic factors on the occurrence of guttation droplets, data for daily maximum, minimum, and average ambient and soil temperatures; RH; and solar radiation were taken at 08.00, 13.00 and 18.00 h from 2 May until 17 July 2019 from a weather station located at the study site (Chatsworth, NJ, USA) All statistical analyses were performed using IBM SPSS Statistics 23.0, except for PCA which was done using Minitab v. 16 (Minitab 2010)
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