“…Most reported surveys of electrophoretic variation in natural populations have provided evidence of nonrandom processes. Biogeographic patterns are often reported to be uniform over wide geographic ranges (11,12,17), or to reflect parallel patterns of environmental variation (18)(19)(20)(21)(22). Analysis of the allele frequencies reported in these studies also reveals nonrandom processes (23), although confusion may arise when data obtained from diverse organisms are pooled (24).…”