Assessing Reproductive Potential In A Federally Listed Species: Differential Staining For Pollen Viability In Spiraea Virginiana

Spiraea virginiana Britton (Rosaceae) is a rare federally-listed, clonal shrub that inhabits riparian zones within the Ohio River drainage. The species often occurs in areas of high disturbance and predominantly uses asexual reproduction to propagate from upstream populations. Although the species' known range suggests that sexual reproduction played an important role in its evolutionary history, sexual reproduction is currently almost non-existent. Pollination studies have shown that the species can produce fertile seeds; however, this has not been witnessed in wild populations. Determining the role of pollen viability with regards to lack of fertile seed formation is an important step towards understanding the sexual reproductive barriers experienced in this species. In this study, pollen viability was determined through in vivo studies on a Motic BA410E research microscope and utilizing a modified Alexander’s stain that differentiates viable and aborted pollen. Inflorescences were collected along the south fork of the New River before anthesis while pollen was mature, but anthers were non-dehiscent. This study aimed to assess pollen viability among populations that were collected along this river drainage to help determine if pollen viability is a major contributing factor to sexual reproductive barriers within this species.