Effect of inbreeding on salinity tolerance in the guppy (Poecilia reticulata)

This experiment was designed to study the relationship between different le vels of inbreeding and observed inbreeding depression for salinity toleranc e, one of the most important tolerances to environmental conditions, in the guppy (Poecilia reticulata). Two generations of full-sib mating and six ge nerations of mating in the n = 10 produced individuals with an expected lev el of inbreeding coefficient of 0.375 and 0.265, respectively. A significan t decrease in the mean value of salinity tolerance, expressed by survival t ime in 35-ppt seawater, was observed in both the full-sib mated Line and th e closed line of it = 10, indicating inbreeding depression for salinity tol erance. The mean and coefficient of variation (C.V.) of salinity tolerance decreased linearly with the increase in inbreeding coefficient with a rate of 9.1% and 10.1% per 10% increase in the inbreeding coefficient, respectiv ely. Analyses among seven lines of the full-sib matings indicated that inbr eeding caused the larger reduction of the means observed in the lines havin g higher salinity tolerance at the P generation and decreased both deviatio ns of the means among the lines and CN. within each line. The linear decrea se in salinity tolerance with an increase in inbreeding coefficient suggest s that inbreeding depression for salinity tolerance results from additive c ombination among the loci responsible for inbreeding depression. (C) 2001 E lsevier Science B.V. All rights reserved.