Ecology of Irion County Buckwheat (Caryophyllales: Polygonaceae)

Eriogonum nealleyi , the Irion County buckwheat, is an endemic plant reported to occur in five counties (Sterling, Irion, Howard, Coke, Tom Green Counties) in Texas. We collected locality data from herbarium specimens, mapped locations for Sterling, Irion, and Tom Green Counties, and then surveyed each site. We found plants at only one site in Sterling County; however, we discovered three additional small populations in the vicinity of the recorded location. These populations were used for our study of the reproductive biology and pollination ecology. Field investigations commenced in September, when plants began flowering, and continued to November, when the last fruits matured. Based on hand pollination tests, the taxon appears to be self-incompatible, although fruit set was very low in both self and cross pollination tests. The flowers are very small, 1.5-2mm in diameter at anthesis, and occur in tight clusters in a cup-shaped involucre. Both of these features made marking and tracking results from crosses very difficult. Flowers exhibit both physical and temporal mechanisms for preventing self-pollination. Anther dehiscence occurs first. At this time the three styles are curved downward, around the pistil. Tests using peroxtesmo esterase indicator papers showed stigmas did not become receptive until later in the floral phenology when styles had straightened and were erect in the flower. At this stage, little pollen remains in the anthers and filaments now bow outward, away from receptive stigmas. Flowers produce ample, conspicuous nectar but insect visitors were rare on most observation days. Studies will resume in Fall 2017.