E. De Matthaeis et al., Isolation by distance in equilibrium and nonequilibrium populations of four talitrid species in the Mediterranean Sea, EVOLUTION, 54(5), 2000, pp. 1606-1613
Allozymic variation at 21-23 loci was studied in 28 populations of Talitrus
saltator, 23 populations of Orchestia montagui, 13 populations of O. steph
enseni, and five populations of Platorchestia platensis from the Mediterran
ean Basin. Different levels of gene flow (Nm(e)) were detected within each
species at the scale of the whole Mediterranean: O. montagui and P. platens
is had low population structure, with levels of Nm(e) greater than or equal
to 1, whereas the T. saltator and O. stephenseni populations have values o
f Nm(e), < 1. The relationship between Nm(e), and geographic distance was a
nalyzed to test for the presence of an isolation by distance pattern in the
spatial genetic variation within each species. A model of isolation by dis
tance is useful to describe the pattern of genetic structuring of study spe
cies at the scale of the whole Mediterranean: geographic distance explained
from 28% to 70% of the variation in gene flow. In the Aegean area all spec
ies showed an island model of genetic structuring regardless of the levels
of gene flow.