Data from: Persistent postmating, prezygotic reproductive isolation between populations

Studying reproductive barriers between populations of the same species is
critical to understand how speciation may proceed. Growing evidence
suggests postmating, prezygotic (PMPZ) reproductive barriers play an
important role in the evolution of early taxonomic divergence. However,
the contribution of PMPZ isolation to speciation is typically studied
between species in which barriers that maintain isolation may not be those
that contributed to reduced gene flow between populations. Moreover, in
internally fertilizing animals, PMPZ isolation is related to male
ejaculate – female reproductive tract incompatibilities but few studies
have examined how mating history of the sexes can affect the strength of
PMPZ isolation and the extent to which PMPZ isolation is repeatable or
restricted to particular interacting genotypes. We addressed these
outstanding questions using multiple populations of Drosophila montana. We
show a recurrent pattern of PMPZ isolation, with flies from one population
exhibiting reproductive incompatibility in crosses with all three other
populations, while those three populations were fully fertile with each
other. Reproductive incompatibility is due to lack of fertilization and is
asymmetrical, affecting female fitness more than males. There was no
effect of male or female mating history on reproductive incompatibility,
indicating that PMPZ isolation persists between populations. We found no
evidence of variability in fertilization outcomes attributable to
different female x male genotype interactions, and in combination with our
other results, suggests that PMPZ isolation is not driven by idiosyncratic
genotype x genotype interactions. Our results show PMPZ isolation as a
strong, consistent barrier to gene flow early during speciation and
suggest several targets of selection known to affect ejaculate-female
reproductive tract interactions within species that may cause this PMPZ
isolation.