Bryophyte assembly rules across scales

Understanding how species assemble into communities is a central issue in community ecology. So far, most studies have focused on the assembly mechanisms of vascular plant communities, while the role of deterministic (environmental filtering and biotic interactions) and stochastic (e.g., dispersal limitation) processes structuring bryophyte assemblages remains poorly understood.
To evaluate how different assembly processes shape bryophyte communities in mountain streams, we examined functional trait patterns across spatial scales and along environmental gradients. To do so, we sampled 754 microhabitat plots (0.25 m2) nested within 165 sites (100-m long stream segments) and 13 sub-basins, located in the northwest and central-west of Portugal. At each spatial scale, observed functional diversity indices (Functional Richness and Rao’s quadratic entropy) were compared to random expectations derived from null models, followed by the analysis of changes in functional trait patterns along env..., The study was carried out in streams distributed 13 throughout 13 sub-basins, located in the northwest and central-west of Portugal.
Fieldwork was conducted from May 2003 to October 2008 in 165 sites, selected according to the spatial distribution and density of river networks within each sub-basin. Sites were also chosen to span the range of hydromorphological conditions.  In each site, bryophyte species abundance was registered as percentage cover using sampling plots of 0.25 m2 (0.5 m x 0.5 m), placed in distinct microhabitats recognized in the streambed structure, with different levels of submersion and substrate stability. Thus, within each site, each microhabitat plot represents a distinct micro-hydromorphological unit. The number of microhabitat plots in each of the 165 sites was proportional to the diversity of micro-hydromorphological conditions (1–18 plots per site). In total, this survey resulted in 754 microhabitat plots. At the site scale, species abundance was estimated as...,