Abstract :
[en] Aim Bryophytes exhibit the lowest rates of endemism among biota in Macaronesia and differ in diversity patterns from angiosperms by the widespread occurrence of endemics within and among archipelagos. In this study, we test the hypothesis that high dispersal ability erodes phylogeographic signal and hampers the chances of diversification in bryophytes using the leafy liverwort Radula lindenbergiana as a model.
Location Macaronesia, Europe, South Africa
Methods 84 samples were collected across the species distribution range and sequenced at four cpDNA loci (atpB-rbcL, trnG, trnL, and rps4). Phylogenetic reconstructions and Bayesian ancestral area reconstructions were used in combination with population genetic statistics (H, Nst, Fst) to describe the pattern of present genetic diversity in R. lindenbergiana and infer its biogeographic history.
Results The two regions with the highest haplotypic diversity are Madeira and the Canary Islands. Ancestral area reconstructions suggest that Macaronesia was colonized at least twice independently and that the haplotypes currently found in Western Europe share a Macaronesian common ancestor. Whilst analysis of molecular variance and Nst statistics indicate that present-day patterns of genetic variation have a globally significant biogeographic component, Fst values among Macaronesian archipelagos, North Africa, and the Iberian Peninsula, were not significant.
Main conclusions The apparent lack of speciation amongst Macaronesian bryophytes hides actual patterns of diversification at the molecular level. The occurrence of Canarian endemic haplotypes across several islands, along with the non-significant Fst and Nst among islands, North Africa and the Iberian Peninsula, suggest intense dispersal. The occurrence of endemic haplotypes suggests, however, that dispersal does not completely prevent diversification. The high diversity found among Macaronesian haplotypes, together with the Macaronesian origin of all the haplotypes found in Western Europe, suggests that Macaronesian archipelagos could have served as a refugium during the Quaternary glaciations and as a source for re-colonization of Europe.
