The ur-Iris likely had purple flowers, pollinated by insects for nectar

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The ur-Iris likely had purple flowers, pollinated by insects for nectar
Selected Iris species. (A) I. atropurpurea; (B) I. bismarckiana; (C) I. fulva; (D) I. historio; (E) I. loretti; (F) I. lutescens; (G) I. mesopotamica;(H) I. petrana; (I) I. pumila; (J) I. reticulata; (K) I. setosa; (L) I. virginica Credit: The authors

The genus Iris of flowering plants—named after the Greek rainbow goddess because of the variation in flower color—comprises over 300 species across the northern hemisphere, some of which are Vulnerable or (Critically) Endangered on the IUCN Red List of Threatened Species. Due to the poor fossil record, it is not yet known when irises first originated, but scientists believe the genus is only a few million years old, having its closest living relatives in today’s southern Africa.

“We wanted to study the factors influencing and maintaining the outstanding evolutionary divergence in irises, a young but very diverse group. We were especially interested in the evolution of flower color and morphology, because these are key traits for pollinator attraction,” says Dr. Yuval Sapir from the School of Plant Sciences of Tel Aviv University, Israel, corresponding author of a new study in the open-access journal Frontiers in Plant Science.

Modern Iris species mostly live in (semi-)deserts or mountainous environments, although some specialize in moist or wet habitats. They are typically pollinated by insects, but a few species are visited by birds, and often capable of self-fertilization (“self-compatible”). Their flowers have three upright petals, the “standards”, and three hanging sepals, the “falls”. Standards and falls aren’t always the same color, and can be dark purple, violet, pink, yellow, or white. Their lower parts form a pollination tunnel that contains both the stamens and styles, whose entrance may be marked by a ridge or “crest”, part of the falls. Crests are thought to function as guides to lead potential pollinators to the