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Because the brain is one of the energetically most expensive organs of animals, trade-offs have been hypothesized to exert constraints on brain size evolution. The expensive-tissue hypothesis predicts that the cost of a large brain should be compensated by decreasing size of other metabolically costly tissues, such as the gut. Here, we analyzed the relationships between relative brain size and the size of other metabolically costly tissues (i.e., gut, heart, lung, kidney, liver, spleen or limb muscles) among four Fejervarya limnocharis populations to test the predictions of the expensive-tissue hypothesis. We did not find that relative brain size was negatively correlated with relative gut length after controlling for body size, which was inconsistent with the prediction of the expensive-tissue hypothesis. We also did not find negative correlations between relative brain mass and relative size of the other energetically expensive organs. Our findings suggest that the cost of large brains in F. limnocharis cannot be compensated by decreasing size in other metabolically costly tissues. [ABSTRACT FROM AUTHOR]

Bergmann’s rule states that within a species of endotherms smaller individuals are found in warmer conditions, which is consistent for nearly all endotherms, while in ectotherms body size patterns are less consistent. As ectothermic vertebrates, the morphology of amphibians is likely impacted by climatic conditions. Here, we examined latitudinal variation in body size in the ranid frog, Fejervarya limnocharis, based on literature and our own data on mean body size of 3637 individuals from 50 populations and average age of 2873 individuals from 40 populations in China. The results showed that body size was positively correlated with environmental temperature, but not with precipitation. Body size was negatively correlated with latitude among populations in this species, which supported the inverse of Bergmann’s rule. Our findings suggest that a larger body size in low-latitude populations is associated with a longer growing season related to the higher environmental temperature. [ABSTRACT FROM AUTHOR]

In animals, the amount of nutrients acquired through foraging and the proportion of metabolisable energy gained is reflected in the digestive tract length. This digestion theory predicts that the consumption of food with high content of indigestible material will lead to increased gut dimensions. Here, we analyzed geographic variation in digestive tract length related to diet among 14 Fejervarya limnocharis populations to test the digestion theory. Relative digestive tract length significantly differed between males and females and among populations. The relative length of the digestive tract increased with altitude. We also found a positive correlation between the proportion of plant material and digestive tract length for both sexes, which is consistent with the prediction of the digestion theory. Our findings suggest that variation in temperature associated with altitude affects food composition, and, thereby ultimately gut morphology of individuals. [ABSTRACT FROM AUTHOR]