Responses to spring rainfall and shading in moonworts: trait variability and the dynamics of a genus community

Abstract

In the context of ongoing global changes, long-term demographic monitoring data is crucial to assess the viability of natural populations. Such data is particularly important when large fluctuations in population size obfuscate background demographic trajectories. Here, we report results from the first 5 years of a long-term monitoring of a moonwort (Botrychium, Ophioglossaceae) community in Bic National Park, eastern Canada. Our objectives were to provide a first estimate of the composition, size, and demography of the moonwort colonies and to evaluate the putative influence of meteorological and microenvironmental variables on the density of aboveground sporophytes and sporophyte trait variability. Individuals were identified to the species level and tallied in each colony (n = 16 colonies) for the first 3 years (2019–2021) and then marked, monitored, and measured in permanent sample plots (n = 27 plots) for the last 3 years (2021–2023). Although colonies did not vary in composition (n = 8 Botrychium species), the number of emerged individuals differed yearly. Moonwort abundance, re-emergence, and trophophore height were associated with rainfall during the period of sporophyte emergence. Post-drought recovery occurred readily, which might reflect rapid recruitment or dormancy in Botrychium. Moonwort abundance declined as shrub cover and herbaceous vegetation height increased whereas trophophore size was smaller under closed tree canopy. Our results suggest spring rainfall as the limiting factor in opened habitats, whereas competition for sunlight may be limiting under closed canopy. The sizable and species-rich moonwort community of the Bic National Park provides key insights into Botrychium ecology and community dynamics.