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INTRASPECIFIC VARIABILITY IN LIFE HISTORY TACTICS: AN ANALYSIS OF HOLBROOKIA MACULATA AND SCELOPORUS UNDULATUS IN THE SANDHILLS OF NEBRASKA
Abstract
Factors affecting the expression of life history traits in the iguanid lizards, Holbookia maculata and Sceloporus undulatus, were studied at a Sandhills prairie in western Nebraska. In one study, the potential affects of interspecific competition were assessed through reciprocal removal experiments. To test for competition, the response of each species to the removal of the other species was compared to a control grid on which both species were present. The variables analyzed for the effects of competition were population density, survivorship, growth rate, size-specific body mass, home range size, and habitat association. Only the survivorship of adult Sceloporus was suggestive of competitive interaction between the two species. In a second study, the reproductive patterns of Holbrookia and Sceloporus were monitored during 1978, 1981, and 1982. Both species demonstrated significant between-year differences in reproductive potential. Each year, yearling Holbrookia produced one clutch while older Holbrookia produced two clutches. The first clutch of older Holbrookia was significantly smaller in 1978 than in 1981 and 1982. There was no significant among year difference in the size of the second clutch or in the size of the one clutch produced by yearlings. Sceloporus, while showing little variation in clutch size among years, produced two clutches in 1978 and 1982 and three clutches in 1981. Unlike previous reports of between-year variation in reproduction of lizards, the variation was not attributed to differences in resource abundance. Alternatively, it is suggested that temperature, due to its effect on assimilation efficiency, is the most important factor inducing proximate variation in Nebraska lizards. Energy budgets were constructed and reproductive efforts calculated for both species. Analysis of reproductive effort indicated little between-year variation for Holbrookia while reproductive effort of Sceloporus was much more variable among years. The implications of differential plasticity in reproductive effort among the two species are discussed. A model is presented which defines the relationship between resource availability and physiological effiency due to temperature and their effect on variation in life history traits. Other studies of reproduction and competition in lizards are analyzed in terms of the model.
Subject Area
Ecology
Recommended Citation
JONES, STEVEN MATTHEW, "INTRASPECIFIC VARIABILITY IN LIFE HISTORY TACTICS: AN ANALYSIS OF HOLBROOKIA MACULATA AND SCELOPORUS UNDULATUS IN THE SANDHILLS OF NEBRASKA" (1983). ETD collection for University of Nebraska-Lincoln. AAI8404814.
https://digitalcommons.unl.edu/dissertations/AAI8404814