Meyer, E. M.; Galloway, L. F.; Eckert, A. J.

An \'\'abominable mystery\'\': angiosperm sexual systems have been a source of both interest and frustration for the botanical community since Darwin. The evolutionary stability, overall frequency, and distribution of self-fertilization and mixed-mating systems have been addressed in a variety of studies. However, there has been no recent study which directly addresses our knowledge of mating systems across families, the adequacy of existing data, or the potential for biases. Here, we present an updated dataset of mating systems across flowering plants covering 6,781 species and 212 families. We find that the vast majority of our data on mating systems comes from a small number of disproportionally-sampled families, and that families with significant proportions of dioecious or monoecious species are much more likely to be undersampled. This suggests that systematic study bias may mean we know less about this vital facet of plant life than we think.