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Abstract
Understanding the mechanisms and patterns of how energy is allocated into the reproductive components of offspring size and number is central to life-history theory. I examined the utility of X-ray photography for determining offspring size and number in freshwater turtles then used X-ray photographs from a long-term mark recapture study to investigate hypotheses of reproductive allocation in three species. Patterns of reproductive allocation varied markedly within and among species. Overall, egg size varied as a function of maternal body size and age, intra-annual clutch frequency, allocation of continuous resources into integral numbers of offspring, and environmental variation. Clutch size varied with maternal body size, clutch frequency, and environmental variation. I examine how effectively the data support theoretical models of reproductive allocation, identify limitations of fundamental biological findings necessary to address the issues, and suggest empirical research that will enhance future consideration of the topic.