Genomic tools to inform restoration strategies of three species of Calamagrostis in Canada’s Northwest Territories

Background/Question/Methods

Negative environmental impacts associated with vegetation decline have triggered an increase in the restoration efforts of critical landscapes. Arctic ecosystems are under extreme ecological pressure from extensive natural resource extraction combined with warming at a rate 2-3 times faster than the mean increase in global temperature. Local adaptation can be an important consideration in plant restoration, but for most native populations inhabiting arctic ecosystems, the question of “how local is local?” remains unexplored. A lack of data on genetic diversity and population structure hinders the ability to successfully establish restoration sites as genetic variation is necessary for evolutionary change to occur. Species in the Calamagrostis Adans. genus are perennial rhizomatous grasses that occur primarily in cool-temperate regions of the world. Within North America, C. canadensis, C. stricta and C. purpurascens are widespread across heterogeneous environments. However, taxonomic identification has been complicated by variation in morphology, ploidy, apomixis, and hybridization. We used ddRAD-seq to investigate genome-wide population structure and genetic diversity among 26 collections of C. canadensis (Nf 10), C. stricta (Nf 9) and C. purpurascens (Nf 7) from the Northwest Territories to aid in seed collection and identification of units for restoration projects in the Canadian Arctic.

Results/Conclusions

Our discriminant analysis of principal components (DAPC) grouped individuals into three clusters that represented the three study species. This shows that populations from the C. canadensis, C. stricta and C. purpurascens species are genetically differentiated and highly structured, despite the historically observed variation of life history traits within species. Nevertheless, we found evidence for interspecific hybridization of C. stricta with C. canadensis and C. purpurascens but not between C. purpurascens with C. Canadensis. Our DAPC showed one C. canadensis and one C. purpurascens individuals that clustered with the C. stricta population. Meanwhile, our STRUCTURE analysis identified three individuals with over 40% admixed ancestry and five individuals with over 20% admixed ancestry. Despite the presence of hybrids, we found low levels of gene diversity, heterozygosity, and high levels of FIS within each species. Our results suggest that populations of Calamagrostis species in the Northwest Territories might experience moderate rates of hybridization between species but low levels of gene flow between populations within each species, possibly due to the large geographic distance separating some populations.