Present address: Department of Environmental Science and Policy, David King Hall MSN 5F2, George Mason University, 4400 University Drive, Fairfax, Virginia, U.S.A.
Timing is everything? Phenological synchrony and population variability in leaf-chewing herbivores of Quercus
Article first published online: 8 FEB 2008
2008 The Authors
Volume 33, Issue 2, pages 276–285, April 2008
How to Cite
FORKNER, R. E., MARQUIS, R. J., LILL, J. T. and CORFF, J. L. (2008), Timing is everything? Phenological synchrony and population variability in leaf-chewing herbivores of Quercus. Ecological Entomology, 33: 276–285. doi: 10.1111/j.1365-2311.2007.00976.x
- Issue published online: 8 FEB 2008
- Article first published online: 8 FEB 2008
- Accepted 9 October 2007First published online 8 February 2008
- plant phenology;
- population dynamics;
Abstract 1. Specialization on ephemeral resources (e.g. new leaves) should produce large annual variation in herbivore population size when the timing of availability of those resources is unpredictable. Despite considerable evidence for impacts of synchrony with budburst on survival of larval Lepidoptera, previous studies of adult Geometridae and Noctuidae found no correlations between insect phenology and population variability.
2. We surveyed larval Lepidoptera feeding on Quercus alba and Q. velutina in Missouri from 1993 to 2003 and examined population variability, measured as the coefficient of variation of population density (CV), in a subset of abundant species. We compared CV values among species whose larvae feed only in spring, early summer, mid-summer, late summer, or all season. We predicted that univoltine species whose larvae eclose and complete development in spring during leaf expansion would have higher variability than species feeding later in the season, having multiple generations, or having longer development times.
3. As predicted and consistent with hypotheses, spring-feeding species had CV values 32% higher than species feeding in summer months. Coefficients of variation were also 34% higher in leaf-rolling and mining guilds compared with free-feeders, suggesting that mobile species may compensate for asynchrony with budburst by dispersing to higher quality plants or plant parts. Multivoltine species, however, did not differ from univoltine species in population variability.
4. Our results suggest that asynchrony with plant phenology and factors that might exacerbate it, such as climate change, will have the largest impacts on the dynamics of spring-feeding Lepidoptera, particularly species with limited mobility.