Opportunity for natural selection with special reference to population structural measures among the Vadde

Crow's indices of opportunity for natural selection have been studied among the Vadde, a fishing community of Kolleru Lake, Andhra Pradesh, India. The sample comes from 15 of the 60 fishing villages. The indices were computed both at the level of village and population units. A village sample of Palle, another fishing group in the area, has also been analysed for the purpose of comparison. An attempt has been made to explain variation in selection indices among the villages using population structural measures. A wide variation is found in both the fertility and mortality indices between the villages. The values were compatible with those found for other fishing groups studied previously, and in the middle of the range observed for the Indian populations (about 100) studied so far. Population structural measures are found to explain a significant amount of variation in Im and It but not in the fertility index.