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Submitted to: Journal of Kansas Entomological Society
Publication Type: Peer Reviewed Journal Publication Acceptance Date: 5/10/2005 Publication Date: 4/19/2006 Citation: Branson, D.H. 2006. Life-history responses of ageneotettix deorum (Scudder) (Orthoptera: Acrididae) to host plant availability and population density. Journal of Kansas Entomological Society. 79(2):146-155. Interpretive Summary: The effects of variation in host plant availability and population densities on reproductive allocation in grasshoppers have received relatively little attention. The effect of increased host plant availability and population density on survival and reproductive allocation were examined in a widely distributed grasshopper, Ageneotettix deorum (Scudder). The experimental treatments consisted of ambient-level and fertilized vegetation with two A. deorum density treatments in a 2x2 factorial design. Both food plant availability and population density played important roles in the observed life history variation. Density-dependence was evident in average and proportional survival. Although the rate of egg pod production was not density-dependent, density-dependence was evident in egg pod size. Average survival did not respond to food plant availability, but reproduction was limited by host plant availability in the ambient-level. Food limited A. deorum with ambient-level resources produced egg pods more slowly and laid smaller egg pods. The rate of egg pod production averaged 64% higher with fertilized vegetation than with ambient vegetation. Given the larger reproductive responses to host plant availability than to initial density, the availability of higher protein host plants may have been the primary limiting factor for egg production. Variation in host plant availability has a much larger effect on recruitment and population dynamics than would be predicted based on survivorship alone. Technical Abstract: The effects of variation in host plant availability and population densities on reproductive allocation in grasshoppers have received relatively little attention. The effect of increased host plant availability and population density on survival and reproductive allocation were examined in a widely distributed grasshopper, Ageneotettix deorum (Scudder). The experimental treatments consisted of ambient-level and fertilized vegetation with two A. deorum density treatments in a 2x2 factorial design. Both food plant availability and population density played important roles in the observed life history variation. Density-dependence was evident in average and proportional survival. Although the rate of egg pod production was not density-dependent, density-dependence was evident in egg pod size. Average survival did not respond to food plant availability, but reproduction was limited by host plant availability in the ambient-level. Food limited A. deorum with ambient-level resources produced egg pods more slowly and laid smaller egg pods. The rate of egg pod production averaged 64% higher with fertilized vegetation than with ambient vegetation. Given the larger reproductive responses to host plant availability than to initial density, the availability of higher protein host plants may have been the primary limiting factor for egg production. Variation in host plant availability has a much larger effect on recruitment and population dynamics than would be predicted based on survivorship alone. |
