Floral Phenology and Sex Ratio of Piratebush (Buckleya distichophylla), a Rare Dioecious Shrub Endemic to the Southern Appalachian Mountains


Ryan D. Huish

Additional Authors:

Melissa Manow, Conley K. McMullen,


March 2015


Biology, Buckleya distichophylla, phenology, piratebush, plant reproductive dioecism, rare plants, Santalaceae

ABSTRACT Piratebush (Buckleya distichophylla, Santalaceae) is a rare dioecious and hemiparasitic shrub endemic to the Appalachian Mountains of Virginia, North Carolina, and Tennessee. Previous studies on piratebush suggest sexual reproductive deficiency as a possible explanation for the rare and scattered distribution of piratebush and a concern for subsequent population decline. To further investigate the reproductive biology of piratebush, we examined sex ratio and flowering phenology in the densest population of piratebush, found on Poor Mountain in southwest Virginia. Sex ratio data were collected through field surveys along ecological transects. Results show a male-biased sex ratio (61:39) of flowering individuals, with 15% nonflowering. Size data confirm significantly smaller size for nonflowering individuals (p < 0.01), suggesting combined characteristics of size and nonflowering as an indicator of juvenility. Floral phenology data were recorded from 23 males and 20 females in varied representative elevation and aspect gradients. Flower abundance was male-dominant by >24:1. Floral phenology showed individual variation, with males beginning and ending approximately 1 wk before females, but considerable synchrony for the bulk of flower production for about 2 wk from 4 May to 16 May. Average high and low ground surface temperatures from the site are also reported. The widely male-dominant sex ratio and floral abundance, as well as variation in flower production by females, underscore the importance of ongoing investigations into the reproductive and regenerative health of this rare and scattered species.