Insect assemblages change along a gradient of invasion by a nonnative grass |
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Authors: | Andrea R Litt Robert J Steidl |
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Institution: | (1) School of Natural Resources and the Environment, University of Arizona, Tucson, AZ 85721-0001, USA;(2) Caesar Kleberg Wildlife Research Institute, Texas A&M University, Kingsville, 700 University Blvd., MSC 218, Kingsville, TX 78363-8303, USA |
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Abstract: | Because invasions by nonnative plants alter the structure and composition of native plant communities, invasions can alter
the function of ecosystems for animals that depend on plants for food and habitat. We quantified effects of an invasion by
a nonnative grass on the insect community in grasslands of southeastern Arizona. We sampled insects on 54 1-ha plots established
across a gradient of invasion by Lehmann lovegrass (Eragrostis lehmanniana Nees), a perennial species native to southern Africa. Between 2000 and 2004, we captured 94,209 insects representing 13 orders,
91 families, and 698 morphospecies during 2,997 trap nights. Richness of families, richness of morphospecies, and overall
abundance of insects decreased as dominance of nonnative grass increased. With every 100 g/m2 increase in biomass of nonnative grass, the average number of insect families decreased by 5%, morphospecies decreased by
6%, and overall abundance decreased by 14%. In areas dominated by nonnative grass, 2 of 8 orders and 6 of 27 families of insects
were present less frequently and one family was present more frequently; 5 of 8 orders and 6 of 27 families of insects were
less abundant and 3 families were more abundant than in areas dominated by native grasses. As a result, this plant invasion
altered the structure of the insect community, which has consequences for animals at higher trophic levels and for ecosystem
processes, including decomposition and pollination. Because complete eradication of nonnative plants might be possible only
rarely, maintaining stands of native vegetation in invaded areas may be an important practical strategy to foster persistence
of animals in grasslands invaded by nonnative plants. |
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