Assisted migration as a conservation strategy for rapid climate change: Investigating extended photoperiod and mycobiont distributions of Habenaria repens Nuttall (Orchidaceae) as a case study

Brian George Keel (2007)

This dissertation proposes assisted migration (the intentional movement of a plant beyond the boundary of its present range) as a plant conservation strategy in a changing climate and within a fragmented landscape. Orchids are a unique family of plants that have an obligate requirement for mycorrhizal fungi, and therefore, an ideal group to use as a model for plant/microbe conservation in a changing climate. I examined two factors that may influence the application of assisted migration to orchids. I evaluated the effects of an extended photoperiod on orchid seed germination and seedling development (plants migrating to higher latitudes will be subjected to extended photoperiods during the growing season relative to the seed source), and I assessed the range of a specific terrestrial orchid's mycobionts. Habenaria repens Nuttall, a native of the New World tropics and subtropics, was used as a model for North American terrestrial orchids. Habenaria repens seed from Florida was subjected to the photoperiod of three locations, 14.75 h (seed source), 16.25 h (southern Pennsylvania), and 20 h (northern Quebec). Percent seed germination was highest for the 16.25 h photoperiod (37.0%), and lowest for the 20 h photoperiod (15.1 %). After germination, seedlings showed a trend for better growth as the photoperiod was extended with best growth attained under the 20 h photoperiod. To determine the range of H. repens' mycobionts, nylon mesh seed packets that permit fungi to enter and form mycorrhizal associations with the seed were employed as a means of capturing fungi. Seed packets were sown at five sites within the Atlantic coastal plain in North Carolina, Virginia and Maryland, and one site in upstate New York. Retrieved seed packets produced six fungal strains, all tentatively identified as members of the genus Epulorhiza. Findings of this project emphasize that the successful establishment of an orchid population at a particular site, assuming the site is otherwise acceptable for the orchid, is ultimately dependent on the presence of compatible mycobiont strains.