Data from: Hybridization and reproductive isolation between diploid Erythronium mesochoreum and its tetraploid congener E. albidum (Liliaceae)

Polyploidy has played an important role in angiosperm diversification, but
how polyploidy contributes to reproductive isolation remains poorly
understood. Most work has focused on postzygotic reproductive barriers,
and the influence of ploidy differences on prezygotic barriers is
understudied. To address these gaps, we quantified hybrid occurrence,
interspecific self-compatibility differences, and the contributions of
multiple pre- and postzygotic barriers to reproductive isolation between
diploid Erythronium mesochoreum (Liliaceae) and its tetraploid congener E.
albidum. Reproductive isolation between the study species was nearly
complete, and naturally occurring hybrids were infrequent and largely
sterile. Although postzygotic barriers effected substantial reproductive
isolation when considered in isolation, the study species’ spatial
distributions and pollinator assemblages overlapped little, such that
interspecific pollen transfer is likely uncommon. We did not find evidence
that E. albidum and E. mesochoreum differed in mating systems, indicating
that self-incompatibility release may not have fostered speciation in this
system. Ultimately, we demonstrate that E. albidum and E. mesochoreum are
reproductively isolated by multiple, hierarchically-operating barriers,
and we add to the currently limited number of studies demonstrating that
early acting barriers such as pollinator-mediated isolation can be
important for effecting and sustaining reproductive isolation in
diploid-polyploid systems.