Eco-Geography and Phenology Are the Major Drivers of Reproductive Isolation in the Royal Irises, a Species Complex in the Course of Speciation.

The continuous nature of speciation implies that different species are found at different stages of divergence, from no- to complete reproductive isolation. This process and its underlying mechanisms are best viewed in incipient species. Moreover, the species complex can offer unique insight into how reproductive isolation (RI) has evolved.