An Evolutionary Family Tree of the Bearded Irises
This diagram should be regarded as conjectural. It reflects some of the findings of Randolph and Mitra from karyotype analysis, but other relationships shown are more subjective. As far as I know, there has been no thorough study of the genetic divergence of the many species of bearded irises. My hope is that this family tree will at least provide a visual image to suggest the relationships between the various species.
Blue represents the species whose chromosomes are in sets of 12. Light blue represents 2n=24 TT diploids; dark blue represents 2n=4x=48 TTTT tetraploids.
Gold represents the species whose chromosomes are in sets of 8. Light gold represents 2n=16 PP diploids, dark gold represents 2n=4x=32 PPPP tetraploids.
Green represents the amphidiploid PPTT I. lutescens group, with 2n=40.
I. lutescens = I. olbiensis = I. chamaeiris = I. italica
I. reichenbachii = I. balkana = I. bosniaca
I. suaveolens = I. mellita
Some authors (e. g., Brian Mathew) consider some or all of the species listed in the "Germanica Group" as synonyms of I. germanica.
I. aphylla = I. hungarica, I. polonica, I. bohemica
I. pallida = I. cengialtii, I. illyrica, I. dalmatica
I. variegata = I. reginae, I. flavescens, I. rudskyi, I. mangaliae, I. virescens
A number of plants given species names are thought to be natural hybrids:
Germanica Group x Lutescens Group: Florentina, Albicans, Kochii, Kashmiriana (not the species), Germanica (not the species)
I. pallida x I. vaiegata: Plicata, Amoena, Neglecta, Squalens, Swerti, Sambucina
I. aphylla x I. pumila: Barthii (PPPT), Binata (PPPT), Benacensis (PPTT)
Modern garden varieties of TBs and BBs are TTTT tetraploids derived largely from Ii. germanica, pallida, and variegata.
Modern garden varitieties of SDBs, MDBs, and IBs are mostly derived from I. pumila and tetraploid TBs/BBs.
Modern diploid MTBs are derived from TT diploid species, in particular I. variegata.
Modern tetraploid MTBs are derived from TBs, BBs, and I. aphylla.
"Karyotype Analysis of Bearded Iris," J. Mitra, Botanical Gazette 117:4, 1956.
The World of Irises, Bee Warburton and Melba Hamblen, eds. AIS, 1978.
Brian Mathew, The Iris. Timber Press, 1981.
Unless otherwise noted, all text and illustrations copyright Tom Waters and all photographs copyright Tom or Karen Waters. Please do not reproduce without permission.