Data files, R code, and figures for Isolating barriers at the early stages of speciation in trees: insights from Metrosideros polymorpha on Hawaiʻi Island

The reproductive barriers that evolve early and drive plant speciation are not often known, but reported in recent reviews to be predominantly prezygotic. We used varieties of the hyper-variable landscape-dominant tree, Metrosideros polymorpha, to uncover the post-pollination, prezygotic and F1-stage post-zygotic barriers emerging at the early stages of speciation in trees.We report four contrasting patterns and strengths of predominantly postzygotic isolation in the four taxon pairs examined, including protracted F1 mortality. These results highlight the importance of intrinsic postzygotic barriers at the early stages of speciation in trees and the extended temporal scale over which they may appear in long-lived species.