Intra-species ecological divergence in irises

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.

Flower of Iris atropurpurea in NET population and distribution map of I. atropurpurea. — (A) Flower of *Iris atropurpurea* in NET population. (B) Distribution map of *I. atropurpurea*. All known populations are marked as dots. Red dots represent extinct populations. Circles denote populations used in this study and their codes. (C) Flowers of *I. atropurpurea* covered to prevent natural pollination. (D) Premature seeds of *I. atropurpurea*, representing the range of seed sizes. (E) Premature seeds in a capsule. Six of the seeds (marked with arrows) are viable.

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.