Investigations Into the Reproductive Biology of the Southern Appalachian Endemic Piratebush (Buckleya distichophylla): Pollination Biology, Fruit Development, and Seed Germination

Published:

April – 2019

Author

Ryan Huish

Additional Authors

Amy E. Faivre, Melissa Manow, Conley K. McMullen

Endemic to the mountains of Tennessee, North Carolina and Virginia, piratebush (Buckleya distichophylla, Santalaceae) is a rare, dioecious, hemi-parasitic shrub with a scattered and isolated distribution. Vegetative reproduction and few visible seedlings within the densest population of piratebush on Poor Mountain in southwest Virginia emphasize the need for research into this species’ reproductive biology to inform conservation strategies. Pollination data showed no evidence for wind pollination; instead multiple diurnal floral visitors to staminate flowers were observed. Fluorescence microscopy of stigma and styles on initiated fruits revealed almost 95% with pollen deposition. Most initiated fruits (52%) had tube growth continue to the base of the style, indicating potential fertilization. Pollination experiments showed outcrossing was necessary for fruit set. Non-pollinated flowers in bags had 0% fruit development, whereas fruit development in both open pollinated (86%) (p< 0.0001) and hand pollinated (65%) treatments (p<0.0001) were significantly greater. Embryo viability analysis indicated 73% of seeds had healthy embryos. Germination trials indicated that seeds must undergo stratification for successful germination. Germination for control (70.9%) and 10 min bleach (72.6%) treatments were significantly higher than mechanically scarified fruits/seeds (27.2%), suggesting a potentially negative impact that rodent gnawing would have on seed germination. Further, evidence of heavy seed predation was observed. These results suggest that there may be sufficient pollinators, successful outcrossing and seed development, and that embryos are viable and have the potential to germinate, but imply that seed predation may be a key reproductive constraint for piratebush.

Keywords

Buckleya distichophylla, piratebush, reproductive biology of rare plants, Santalaceae, seed predation and germination