Predators have long been valued for their role in controlling outbreaks of insect species that can inflict considerable damage to their specific host plant species. Ecological science is now theorizing that by protecting plants from damage, predators may play an even more critical role in ecosystems than previously thought. Different predator species prefer different kinds of insect prey. Such preference may steer which combinations of plant species (biodiversity) survive in an ecosystem. The level of plant biodiversity, in turn, can impact the level of important ecosystem services like the breakdown of organic matter and cycling of important nutrients such as nitrogen, which then feeds back to influence the production rate of living plant tissue. This study will experiment with different spider predator species and grasshoppers in a grassland ecosystem. It will test the hypothesis that each predator species will uniquely affect grasshoppers which, in turn, uniquely affects the composition of plant species and the level of ecosystem services. In addition, it will measure how individual predator species effects on the ecosystem add up. The study will hold different predator species, individually and in combination, in experimental field plots and measure the abundance of grasshoppers, the abundance of naturally occurring plant species, and the rates of organic matter (plant leaf litter) decomposition, nitrogen cycling and plant production. The study will help to increase the precision of biological control measures by identifying which combinations of predator species best achieve desired levels of plant species diversity and plant production in grassland ecosystems.
