Tuesday, May 28, 2013

Iris versicolor

Dr. Edgar Anderson

Origin of species via hybridization

In the 1920s and 30s Dr. Edgar Anderson of the Missouri Botanical Gardens (MOBOT) and Associate Professor of Botany, Washington University of St. Louis made extensive field trips to examine the variation of form and structure in Iris versicolor, common blue flag. He diagrammed the great amount of genetic variation in natural populations. He found two species rather than one and began to examine how one evolved from the other. His conclusions found more variation within populations of one species than differences between the two species; another species had been involved in the evolution of Iris versicolor. The answer was through hybridization followed by chromosome doubling to produce a fertile, stable, true-breeding amphidiploid. (Melding of the complete chromosome set from each parent.)  His data included chromosome counts and concluded that Iris versicolor (2n = 108), was the amphidiploid progeny of Iris virginica (2n = 70) from the Mississippi valley and Iris setosa var. interior (2n = 38) of the Yukon. Today I. versicolor occurs almost entirely in territory that was covered by ice during Pleistocene glaciation; while I. virginica occurs in untouched areas south. I. setosa var. interior currently growing northwest of the glaciated area, was pushed south by glacial formation into the range of I. virginica. For more information regarding Dr. Anderson visit: http://www.nasonline.org/publications/biographical-memoirs/memoir-pdfs/anderson-edgar.pdf
Dr. Edgar Anderson
Every year of the past decade I have yearned to follow the footsteps of Dr. Anderson following the bloom season up the Mississippi valley. I have wanted to examine the implications of 90 years and 200 million more humans affecting the environment colonized by Iris versicolor. It could also prove useful to collect variation where it still exists to aid hybridization efforts.

Iris versicolor and I. virginica have always been appreciated for their beauty and medicinal qualities. On the practical side these irises are now included in rainwater gardens and vegetative filter strips. Scientific analysis identified these plants as hyperaccumulators, removing pesticides from soils and able to reduce levels of commonly and widely used insecticides and fungicides.
A principle example of the origin of species, of growing practical and aesthetic value, this iris deserves our foremost consideration.  

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