Abstract
Life history theory predicts that animals often produce fewer offspring of larger size and indicate a stronger trade-off between the number and size of offspring to cope with increasing environmental stress. In order to evaluate this prediction, we tested the life history characteristics of Bufo minshanicus at eight different altitudes on the eastern Tibetan Plateau, China. Our results revealed a positive correlation between female SVL and clutch size or egg size, revealing that larger females produce more and larger eggs. However, high-altitude toads seem to favor more offspring and smaller egg sizes when removing the effect of female SVL, which is counter to theoretical predictions. In addition, there was an overall significantly negative relationship between egg size and clutch size, indicative of a trade-off between egg size and fecundity. Therefore, we suggest that higher fecundity, rather than larger egg size, is a more effective reproductive strategy for this species of anuran living at high-altitude environments.
Highlights
Life-history theory suggests that females should be able to optimize their allocation of resources between current breeding efforts and future survival[1]
Clutch size increased with increasing altitude and latitude
There was a negative association between clutch size and egg size, indicating a population-level trade-off between fecundity and egg size
Summary
Life-history theory suggests that females should be able to optimize their allocation of resources between current breeding efforts and future survival[1]. The trade-off between offspring number and size suggests that selection will produce more small eggs or abundant larvae under scarce resources and stressful environments, which is known as r-selection[9]. We investigated altitudinal variations in Bufo minshanicus life history traits, focusing on a trade-off between egg size and clutch size. Bufo minshanicus is a species endemic to high altitude regions of the eastern Tibetan Plateau in China. Widespread species that occupy many thermal environments provide testable models for understanding the evolution of life-history responses to altitude. Studies across altitudes provide a good approach to understand life-history evolution in stressful environments. We predict that altitude would be (1) negatively correlated with clutch size, (2) positively associated with egg size, and (3) positively correlated with female SVL. We tested the prediction that (4) there is a trade-off between egg size and clutch size
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