The genetic structure of the flatfish Solea vulgaris was investigated
on several spatial scales and at the temporal level through analysis o
f electrophoretic variation at 8 to 12 polymorphic enzyme loci. No dif
ferentiation was apparent at the temporal scale. Some differentiation
was detected at and above the regional scale. Isolation by distance wa
s evidenced by the significant correlation between genetic and geograp
hic distances, and by the consistency of the results of multiple-locus
correspondence analysis with geographic sampling patterns. The analys
is suggested that the geographic unit of population structure (i.e. a
geographical area corresponding to a panmictic or nearly panmictic pop
ulation) lies within a radius of the order of 100 km. The isolation-by
-distance pattern in S. vulgaris contrasted with the known genetic str
uctures of other flatfish species of the northeastern Atlantic and Med
iterranean in a way that may be related to the range of their respecti
ve temperature tolerances for eggs and larvae.