Friday, May 16, 2008

St. Francois Mountains' dwarf spiderwort

As I write, scattered throughout the dry igneous woodlands of Missouri's St. Francois Mountains blooms the diminutive purple flower of Tradescantia longipes, known locally as dwarf spiderwort. Found in the igneous hills of the Ozark Highlands of Missouri and Arkansas' Ouachita Mountains, T. longipes represents one of many Ozark endemic wildflowers with close relatives in the genus of more common (though no less exquisite) plants. As I discovered today, even, poking up through the rich sedge layer in my Columbia backyard is a thick stand of the taller, rangier spiderwort (T. ohiensis), slated for transplanting to the front yard where it will share company with literally hundreds of wild geranium plants.

But in the dappled sunlight of an afternoon in the St. Francois Mountains, the common occurrence of the deep, rich purple flowers of dwarf spiderwort reminded me that I was, indeed, in a safe place, a managed woodland that cradled biodiversity. The short, squat habit of the plant is vastly different from the common spiderworts. Gazing deep into the flowers with my trusty hand lens, I discovered stamens covered in thick bright yellow filaments (I tried, repeatedly in vain, to capture it in a photo, but my great camera gave me an emphatic "no!" to the close up command). Apparently, the yellow stamen hairs, coupled with the pleasant scent of the flower itself attract its main pollinators, bees and syrphids (though other pollinators sometimes include other Diptera, Coleoptera, some beetles, ants, and rarely butterflies). The fringed stamen provides a function other than attraction; the navigation obstacles provided by the lugubrious hairs may cause bees to drop the pollen particles onto the hairs, which then retain the pollen and allow the flower to (however inadvertently) pollinate itself. The stamen hairs may also serve as footholds for the insects, or even determine insect behaviour altogether. Whether accidental or spontaneous, the stamen hairs offer some semblance of reproductive integrity.

The stamen hairs in another species of Tradescantia serve as indicators of radiation and chemical pollution. The normally blue stamen hairs turn pink when under the influence of radiation or chemical pollution. The stamen hair test has proven so fool proof that Kyoto University and Brookhaven National Laboratory have formalized stamen hair mutation tests as a means to detect gene mutation due to chemical or radiation pollution.

But far away from Kyoto or any lab to speak of, the thriving population of T. longipes in the St. Francois Mountains is in its full glory these days, awaiting honeybees who have been documented gorging on the pollen of over 73 flowers consecutively.

From my 100+ pictures from a big tract of the St. Francois Mountains closed to the public, see a rare-for-the-area dolomite glade, wild hyacinth (Camassia scilloides), and serene dry igneous woodlands, complete with beloved short leaf pine.

1 comment:

Ted M. said...

Hi Allison,

I happened to see this the night before a planned hike in Madison Co. - I'd never heard of dwarf spiderwort but wondered if I might see it. See it I did - I recognized it instantly, and it was a thrill knowing I was looking at a true Ozark endemic. I'll be including pics in my forthcoming post about the day.

Serendipity at its finest!