Evaluating pollination ecology of Pityopsis ruthii, an endangered southern Appalachian species

An important prerequisite for understanding a species is knowledge of its breeding system. Because reproductive patterns determine the genetic structure of future generations, this knowledge is crucial to plan conservation programs and manage populations of rare plants.  Decline in habitat is the primary cause of reductions to plant populations and their pollinators, which leads to further decline from genetic problems such as drift and inbreeding depression. Little is known about the endangered riparian perennial Pityopsis ruthii (Small) Small (Ruth’s golden aster), which only occurs along two river systems in the Southern Appalachian Mountains of Tennessee. Investigation of pollinator dynamics and seed set were conducted in fall 2013. Objectives were to 1) collect and identify floral visitors to P. ruthii, 2) assay carried pollen for qualitative estimates of pollination service, and 3) compare pollinator communities across the landscape to an experimental ex situ plot to contribute evidence of pollinator dynamics to gene flow and variability in seed production. Based on this study, the primary pollinators of P. ruthii include Bombus impatiens Cresson and Apis mellifera L., two common eusocial bee species. Evidence suggests that plant populations are not pollen nor pollinator limited, but that genetic differentiation and population size may be limiting sexual reproduction in this self-incompatible species. Implications for conservation include the need for reintroduction of genetically diverse genotypes and to increase plant density to increase seed production. The investigation of pollinator impact on P. ruthii is ongoing.