supported by the National Natural Science Foundation of China (Grant No. 30400047);the Training Fund of Northeast Normal University Scientific Innovation Project (Grant No. 07013);the Jilin Provincial Science and Technology Department (Grant No. 20070558 and 20090575)
Fisher's theory predicts equal sex ratios at the end of parental care if the cost associated with raising offspring of each sex is equal.However,sex ratios have important evolutionary consequences and are often biased...