Professor University of Sherbrooke, Quebec, Canada
Background/Question/Methods
Species’ range limits are thought to be governed by two mechanisms: (i) niche limitations – environmental conditions beyond range limits are insufficient for survival and reproduction, or (ii) dispersal limitations – dispersal ability limits colonization beyond range limits. Understanding the mechanism driving range limits is important for predicting whether environmental change will affect species’ distributions. For species restricted to mountain summits, understanding range limits is timely as there is concern that climatic changes may result in increasingly restricted distributions. Here, we conducted a transplant experiment to examine the effect of niche versus dispersal limitation on the elevational range limit of the Ghost Antler Lichen (Pseudevernia cladonia), an arboreal species restricted to high-elevation mountain summits in Southeastern Québec. In 2019, we transplanted 150 Ghost Antler Lichen individuals at three sites along an elevation gradient in Parc National du Mont-Mégantic, Québec: within the species’ range (high elevation), at the edge (mid-elevation), and beyond its range (low elevation). We monitored the survival and fitness of the transplants over two years via surveys and photos. We predicted that this lichen is niche-limited, and that transplant survival and fitness would be greatest within range and decrease towards the edge and beyond its natural range.
Results/Conclusions
We observed that transplant survival and fitness was the greatest within its range and decreased towards the edge and beyond its range, supporting our prediction that the Ghost Antler Lichen is niche-limited along the elevation gradient. As the global range of this lichen is closely associated with cool and humid coniferous forests, we suggest that the cooler and more humid conditions at the summit are important environmental factors that determine this lichen’s elevational range limit. Our findings suggest that future climatic changes in these montane habitats may result in less suitable habitat for this species. In a regional context, high-elevation, humid forest habitats are uncommon in Southeastern Québec and our study site, Parc National du Mont-Mégantic, is home to a substantial protected population of the Ghost Antler Lichen.
