Outcrossing mating system of the early-divergent moonwort fern (Botrychium lunaria, Ophioglossaceae) revealed in the European Alps

Premise of the Research. Vascular plants depend on sexual recombination for generating new genetic variability to meet environmental needs. Nevertheless, members of the early-divergent fern genus Botrychium (Ophioglossaceae) typically maintain gametophytic selfing and show strong inbreeding within populations. To explain this evolutionary anomaly, the existence of previous or current but undiscovered outcrossing, genetically rich, precursors of the existing genetically depauperate taxa has been hypothesized. 

Methodology. Using allele expression at thirteen independently assorting enzyme loci, we compared allelic diversity and levels of heterozygosity in 471 Botrychium lunaria individuals across sixteen populations in the Alps and Jura Mountains of Switzerland. We examined habitat characteristics influencing mating systems and investigated population genetic structure based on a discriminant analysis of principal components and a graph-theoretic framework. We tested the pattern of is...