Speciation is often described as a continuum, from minor divergence of populations to complete reproductive isolation between species. Within-species population divergence can shed light on the first steps of speciation and the mechanisms underlying it.
Yardeni et al. show that ecological divergence of Iris atropurpurea populations is associated with partial reproductive isolation. They find no spatial pattern of reproductive isolation, suggesting that ecological differentiation is predominant over isolation by distance and reduced gene flow in this species. These findings also have implications for conservation management and genetic rescue of the highly fragmented and endangered I. atropurpurea.