Plant-insect ecologists typically attribute the differences to variation in the nutritional quality or defective chemistry of plant tissues. However, the researchers found that cactus-feeding insects chose host plants based on how the plants allocated resources between growth and reproduction.
In a study appearing in the forthcoming issue of The American Naturalist, Tom E. X. Miller, Andrew J. Tyre, and Svata M. Louda (all of the University of Nebraska, Lincoln) examined herbivore dynamics, specifically why plants aren’t all eaten at the same rate. Plant-insect ecologists typically attribute the differences to variation in the nutritional quality or defective chemistry of plant tissues. However, the researchers found that cactus-feeding insects chose host plants based on how the plants allocated resources between growth and reproduction.
“The crux of our findings is actually quite intuitive”, says Miller. “These insects prefer to feed on flowers, so it’s not terribly surprising that they are abundant on cacti that invest most of their resources in flowers.”
“What was surprising,” Miller adds, “was how one single trait predicted the variation”
The results also have implications for understanding the evolution of plant allocation strategies. Current thinking on the subject says that these strategies are a trade-off between current reproduction and future survival. The finding that plant reproductive allocation can attract enemies means that sex may be even more costly than previously though. This research also has implications for weed control and protection of rare plant species.