Bryophyte diversity on Adirondack alpine summits is maintained by dissemination and establishment of vegetative fragments and spores

Many alpine bryophytes rely primarily if not exclusively on gametophytic fragments for reproduction. The dispersal role of these fragments, however, has not been adequately addressed. The objective of this study was to determine the extent to which fragments disperse on alpine summits and the reproductive viability of those fragments. Airborne diaspores were collected from early spring snow deposits in 2008, 2009, and 2010 from the summit of Mt. Marcy, and from summer propagule traps placed on the summits of Mt. Marcy and Algonquin Peak in 2009 and 2010. All fragments collected were identified to genus and/or species, when possible. To test for reproductive viability, fragments were grown in nutrient agar under ambient conditions for a period of 17 weeks. To detect the presence of spores, collected debris was surface sterilized and cultured on separate dishes containing nutrient agar. A total of 6130 gametophytic fragments, representing 26 species, were collected. Collections were dominated by individual leaves (65%) and leafy branch fragments (32%). Up to 20% of fragments collected were found to be viable, with the majority of growth originating from stem tissue. In contrast, spore production was found to be uncommon to rare. The results of this study provide evidence that Adirondack alpine bryophyte populations are maintained by the production and dissemination of gametophore fragments during both winter and summer months, with infrequent spore production events, perhaps episodically when weather conditions are most suitable. Data also suggest that vegetative propagules may travel longer distances on these summits than originally predicted.