To what extent are bryophytes efficient dispersers?

• Bryophytes are typically seen as extremely efficient dispersers. Experimental evidence suggests that efficient short- and long-distance dispersal coupled with random colonization leads to an inverse isolation effect. Under the latter, a higher genetic diversity of colonizing propagules is expected with increasing isolation, counteracting differentiation beyond the range of short-distance dispersal. • This expectation is tested from a review of evidence on spatial genetic structure and analyses of isolation-by-distance (IBD) at different scales. • A decay of the IBD signal, characterized by non-significant slopes between kinship coefficients and distance, was observed in 2/3 of the investigated datasets beyond 100m. A second slope shift was observed at distances larger than 100km, with a proportion of significant slopes in >50% of the datasets. • The decay of the IBD signal beyond 100m, which reflects the rapid decrease of spore densities with increasing distance from the source, is consistent with the inverse isolation hypothesis. Persistence of a significant IBD signal at medium ranges in 1/3 of the cases suggests, however, that the inverse isolation effect is not a rule in bryophyte spore dispersal. Furthermore, the higher proportion of significant isolation-by-distance patterns observed at scales over 100km likely marks the limits of regional dispersal, beyond which an increasingly smaller proportion of spores travel. • We discuss the differences between experimental and genetic estimates of spore dispersal and conclude that geographic distance remains a significant proxy of spore colonization rates, with major consequences for our understanding of actual migration capacities in bryophytes, and hence, our capacity to model range shifts in a changing world.