How Nutrients Mediate the Impacts of Global Change on Locust Outbreaks

Abstract

Locusts are grasshoppers that can migrate en masse and devastate food security. Plant nutrient content is a key variable influencing population dynamics, but the relationship is not straightforward. For an herbivore, plant quality depends not only on the balance of nutrients and antinutrients in plant tissues, which is influenced by land use and climate change, but also on the nutritional state and demands of the herbivore, as well as its capacity to extract nutrients from host plants. In contrast to the concept of a positive relationship between nitrogen or protein concentration and herbivore performance, a five-decade review of lab and field studies indicates that equating plant N to plant quality is misleading because grasshoppers respond negatively or neutrally to increasing plant N just as often as they respond positively. For locusts specifically, low-N environments are actually beneficial because they supply high energy rates that support migration. Therefore, intensive land use, such as continuous grazing or cropping, and elevated ambient CO2 levels that decrease the protein:carbohydrate ratios of plants are predicted to broadly promote locust outbreaks.

Adult Feeding Experience Determines the Fecundity and Preference of the Henosepilachna vigintioctopunctata (F.) (Coleoptera: Coccinellidae)

“…Consequently, emerging adults often exhibit an "innate" preference for certain hosts, despite lacking prior experience with these hosts during the larval stage. Alternatively, herbivores may preferentially feed on hosts whose nutritional content is more beneficial to insect development [32][33][34]. Therefore, examining the impacts of host choice and host switching on the life history performance (lifespan and reproduction) of adult stages offers a comprehensive understanding of the ecological and evolutionary determinants of these behaviors [35].…”