期刊
PROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCES OF THE UNITED STATES OF AMERICA
卷 117, 期 13, 页码 7271-7275出版社
NATL ACAD SCIENCES
DOI: 10.1073/pnas.1920012117
关键词
insect decline; global change; grasshopper; Acrididae; grassland
资金
- NSF [DEB-1556280]
- Konza Prairie LTER NSF grant [DEB-1440484]
Evidence for global insect declines mounts, increasing our need to understand underlying mechanisms. We test the nutrient dilution (ND) hypothesis-the decreasing concentration of essential dietary minerals with increasing plant productivity-that particularly targets insect herbivores. Nutrient dilution can result from increased plant biomass due to climate or CO2 enrichment. Additionally, when considering long-term trends driven by climate, one must account for large-scale oscillations including El Nino Southern Oscillation (ENSO), North Atlantic Oscillation (NAO), and Pacific Decadal Oscillation (PDO). We combine long-term datasets of grasshopper abundance, climate, plant biomass, and end-of-season foliar elemental content to examine potential drivers of abundance cycles and trends of this dominant herbivore. Annual grasshopper abundances in 16- and 22-y time series from a Kansas prairie revealed both 5-y cycles and declines of 2.1-2.7%/y. Climate cycle indices of spring ENSO, summer NAO, and winter or spring PDO accounted for 40-54% of the variation in grasshopper abundance, mediated by effects of weather and host plants. Consistent with ND, grass biomass doubled and foliar concentrations of N, P, K, and Na-nutrients which limit grasshopper abundance-declined over the same period. The decline in plant nutrients accounted for 25% of the variation in grasshopper abundance over two decades. Thus a warming, wetter, more CO2-enriched world will likely contribute to declines in insect herbivores by depleting nutrients from their already nutrient-poor diet. Unlike other potential drivers of insect declines-habitat loss, light and chemical pollution-ND may be widespread in remaining natural areas.
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