Assessing gene flow between Dicranum scoparium Hedw. and D. bonjeanii De Not. (Dicranaceae) using single nucleotide polymorphisms (SNPs)

Abstract While hybridisation in vascular plants has received considerable attention, hybridisation in bryophytes is still relatively understudied. Here we investigate hybridisation between two species from the moss genus Dicranum Hedw. Dicranum scoparium Hedw. and D. bonjeanii De Not. are two moss species of the D. scoparium species complex with partially overlapping morphology and habitat ranges. This study aimed to investigate a potential hybridisation pathway between the two species by using single nucleotide polymorphisms (SNP), morphologically identifying the sex of the specimens and analysing potential sex-specific SNP markers, focusing on southern Sweden. The species differ by D. scoparium being polymorphic and D. bonjeanii monomorphic for the used SNP markers. The SNP markers genetically separate D. scoparium and D. bonjeanii specimens, although admixture between the species was observed on a limited scale. This admixture appears to originate from unidirectional fertilisation of D. bonjeanii by D. scoparium (with a genome skewed towards D. scoparium as a result), possibly followed by back-crossing of first-generation hybrids with D. scoparium. Male expressing specimens were completely absent in the D. bonjeanii samples, making a fertilisation of D. bonjeanii by males of D. scoparium more likely. No sex-specificity was observed in the used SNP markers.