Beyond the Macro: exploring micronutrients in insect communities
Macronutrients are widely considered to be an important limiting factor for insect herbivore populations in grassland ecosystems. However, a potential co-limitation by micronutrients has long been overlooked. We are studying the effect of soil micronutrients on herbivore community composition in coastal tallgrass prairies of Texas with a large-scale multi-nutrient, fertilization experiment manipulating Ca, K, and Na in concert with N and P. Initial results indicated that orthoptera abundance and diversity are co-limited by macronutrients and sodium. To determine if these effects arose through the herbivores feeding more heavily on plants with NP and Na added, we used in-lab choice trials with seven species of orthoptera from three feeding guilds with leaves from four plant species (2 grasses and 2 forbs) that were grown in treatments with either ambient soil nutrients or Na, NP, or Na plus NP added. We then determined how much each individual ate of each treatment leaf at the end of the 48 hour trial. With no preference and a choice of 4 leaves, each leaf should make up on average 25% of each individual’s total consumption. We compared each individuals feeding to these expected amounts and used pairwise t-tests to determine whether preferences existed. Pooling across all individuals, orthopterans chose the NP+Na leaves significantly more than any other leaf type. This finding suggests that orthopterans respond directly to leaf chemistry changes arising from our treatments and have important implications for management practices: orthopterans are considered major pests to agricultural systems and are controlled with billions of dollars of pesticides annually. However, because NP and Na in soils are both enhanced with current agricultural practices, our findings suggest that humans could actually be causing these insect herbivores to thrive and become abundant in agricultural systems by adding these limiting nutrients.
Kathleen A Kargl, Chelse M Prather
Primary Advisor's Department
Stander Symposium poster
"Beyond the Macro: exploring micronutrients in insect communities" (2018). Stander Symposium Posters. 1242.