Scientific Note: Facultative Perenniality in the Dwarf Sundew (Drosera brevifolia)

摘要

The dwarf sundew (Drosera brevifolia') occurs from Uruguay to Virginia. Disjunct populations occur in the southeastern U.S. with the northernmost in Kentucky. Despite this wide distribution, relatively little is known about the biology of this species. It has been described as both annual and biennial. The endangered Kentucky population is considered biennial, but occasionally, live, mature plants have dead flower stalks in early autumn suggesting some may be perennial. In 2013, 40 sundews that germinated in the fall of 2012 were marked as they flowered in 2013. They were observed into a third growing season in 2014 until the end of July. Sixteen plants (40%) died after setting seeds in their second growing season, while nine (22.5%) remained alive,flowered, and set seeds again the following year. Seven of these were still alive at the end of July 2014. Fifteen plants were puzzling as the leaves were dead after setting seeds in their second growing season, but were alive May 2014, of which 12 flowered. This study confirms that at least a portion of the Kentucky population of D. brevifolia is perennial. This is probably facultative perenniality because some plants only survive to a third growing season when precipitation falls evenly over the growing seasons and when no hot, dry periods occur. Mild winters without extensive snow cover may contribute to facultative perenniality as well.