Data from: Introgression and parental conflict underlie repeated occurrences of postzygotic isolation

Postzygotic reproductive isolation is often thought to accumulate as a
byproduct of neutral divergence. Yet, it frequently evolves rapidly, in
line with non-neutral evolution. A major driver of intrinsic postzygotic
reproductive barriers is intragenomic conflicts, such as conflict between
maternal and paternal interests in resource allocation to offspring (i.e.,
parental conflict). Parental conflict may underlie hybrid seed
inviability, a common and rapidly evolving reproductive barrier in
angiosperms. Yet, in closely related, hybridizing species, it remains
unclear how intragenomic conflicts and introgression interact to determine
the fate of incompatibility alleles in nature. Here, we explore repeated
incidences of hybrid seed inviability in a rising model: the Mimulus
guttatus species complex. Using an extensive, range-wide crossing survey,
we discover patterns of hybrid seed inviability within the widespread M.
guttatus that are better described by geography than phylogeny. These
patterns of reproductive isolation transgress species boundaries, as
geographically-proximate but phylogenetically-distant species also exhibit
similar patterns of hybrid seed inviability with allopatric populations of
M. guttatus. We find strong support that patterns of reproductive
isolation are consistent with parental conflict. Lastly, we provide
evidence that introgression may underlie shared patterns of hybrid seed
inviability between two species within this complex. Such introgression
could have led to cascading reproductive isolation with other closely
related species, creating a complex landscape of incompatibility. Overall,
this work suggests that parental conflict and introgression can interact
to shape the rapid and repeated evolution of strong reproductive isolation
in the wild.