Models obtained by means of stepwise multiple regression analysis on factors that explained the variation of non-synonymous substitutions (Ka) and amino acid substitutions (Aa) (dependent variables) of pikas, rat and rabbit.

The independent variables were mean January actual temperature (Tjanu, ��C) and altitude (Al, in m). Standardized (��) and nonstandardized (B) regression coefficients and their standard errors are shown. The table provides results from t-tests (t) and associated probability (P) levels.Note: The survival environment of the standard trial animal, rat and rabbit, was according to the feeding conditions in laboratory (altitude = 500 m, temperature = 20��C).