Experimental test of assisted migration for conservation of locally range-restricted plants in Alberta, Canada

Abstract

Given projected rates of climate change, species with limited dispersal may be unable to migrate at the pace necessary to maintain their current climate niches. This could lead to increased risk of extirpation or extinction, especially for locally range-restricted species within fragmented landscapes. Assisted migration has been suggested as a proactive conservation tool to mitigate these risks. We tested assisted migration for Liatris ligulistylis and Houstonia longifolia, two perennial forbs considered ‘vulnerable’ and ‘imperilled’, respectively, in Alberta, Canada, where they are at their northern and western range limits. Both mature plants and seeds were translocated to replicate sites at four geographic locations along a north-south gradient representing the current ranges of the species (central) and areas south (warmer) and north (cooler) of their current range. L. ligulistylis adult plants thrived ∼500 km north of the species current range with survival, growth, and flowering similar to or exceeding performance in the current range, the influence of soil was also tested by comparing the performance of transplanted mature plants in soil from the source location versus the translocation (recipient) site. Plants planted into soil from the source location had increased flower bud production at all sites. Seedling establishment was significantly higher at sites north of the current range, but much lower in the southern locations. These results suggest that L. ligulistylis is in climate disequilibrium, potentially due to migration lags, and that it might be vulnerable to near-future climate vulnerability. For H. longifolia, the influence of flower morph type and location were tested. Only 8 out 130 translocated adult plants survived, five with thrum flowers and three with pin flowers; no seedling establishment was observed in the first growing season, which experienced drier than normal conditions. Among the eight adult plants, seven survived in the central location and one in the north demonstrating specific habitat requirements and conditions that may make this species difficult for translocation and establishment. Overall, locally rare and range-restricted plants with limited dispersal demonstrate climate sensitivity to current conditions and potential for assisted migration, yet species-by-species testing is needed to understand vulnerability and efficacy of this approach.