The presence and strength of post-pollination barriers in an orchid lineage that lacks pollinator specialization

We observed that CPP is stronger than early gametic incompatibility as pollen-pistil incompatibility, despite the latter occurring earlier than CPP. We did not find that species with stronger early gametic incompatibility have less CPP, as expected from a sequential development of these post-pollination barriers. CPP likely existed in the lineage before species separation and has progressively strengthened over the time of species divergence. Instead pollen-pistil incompatibilities may have evolved several times and asymmetrically after species divergence, likely prompted by ecological interactions between species during secondary contact.