Measuring Opportunity For Natural Selection In Two Endogamous Sub Populations Of Andhra Pradesh, South India

Introduction: Natural selection is one of the important evolutionary factors, which brings about a change in the gene pool of a population. This change is brought about by differential fertility and differential mortality. Differential fertility and mortality are due to difference in genetic fitness of individuals which can be determined in terms of viable offspring produced by the individual. These variables operates singly or jointly to determine the fitness of a particular population in a given environment. Objectives: The main object of the present work is to study the extent of variation provided for the natural selection to operate through differential mortality and also to find out the factors responsible for the variation in sub groups of Salis caste population according to Crow’s formula and the modified method suggested by Johnston and Kensinger and also to compare the present findings with some related findings from other populations of the state. Materials and Methods: In the present study, A house to house survey was conducted for demographic information on 520 families of the Sali sub populations (PS-I: 265; PS-II: 255).Data on fertility and mortality were collected through the in-depth interview with each married woman using structured schedules. The index of total selection intensity (I) and its mortality and fertility (Im and If) were calculated by using the original formula of Crow's and the modified method suggested by Johnston and Kensinger. Results: The study was observed that the total index of natural selection using Crow’s method is higher in PS-II (Pattusalis) (0.5625) than PS-I (Padmasalis) (0.3626). The index of selection due to fertility component is more than mortality component in both the subgroups. Johnston and Kensinger’s index showed the same trend of more contribution of fertility component to the total index of natural selection than mortality component. The higher contribution of fertility component to the total index among the two subgroups of Salis supports the contention that due to better living conditions and proper medical care.