Plastid marker variation reveals immigration history in Scandinavian Syntrichia norvegica and S. ruralis (Pottiaceae, Bryophyta)

Abstract

Introduction: Based on previous analyses of Syntrichia norvegica and S. ruralis, the idea of panmictic populations in Scandinavia can be rejected, despite the high dispersal capacities of wind-dispersed spores. We tested, using comprehensive European datasets, whether intraspecific phylogeographical structure reflects glacial and post-glacial history. We expected different entities to indicate immigration from known Late Glacial Maximum refugial areas, and habitat differentiation. Methods: Using plastid markers (atpB–rbcL and rpl16), we investigated 45 and 190 Scandinavian and 17 and 15 non-Scandinavian specimens of Syntrichia norvegica and S. ruralis, respectively. Key results: We revealed four intraspecific entities in Syntrichia norvegica. Two were from the Scandinavian mountains and the Alps, and one from the Scandinavian mountains only. The fourth was widespread across the Scandinavian mountains, the northern lowlands, and the Baltic Sea islands Öland and Gotland. For S. ruralis, we recovered five entities, of which three were from both Scandinavia and the Alps. One of these occurred in strongly calcareous habitats in southern Scandinavia and the Alps and dominated on Öland and Gotland. One entity was widely distributed only in Scandinavia. One was restricted to the border between boreo-nemoral and southern-boreal Scandinavia. Conclusions: The plastid haplotype distribution patterns suggest glacial survival of Syntrichia norvegica and S. ruralis in refugia south, east and possibly within ice-covered areas of Scandinavia. We hypothesise that one S. ruralis entity evolved adaptations to strongly calcareous habitats. The dominance or prevalence of specific haplotypes of both species on Öland and Gotland contributes to the unique biodiversity of these islands.