Data from: Inferring riverscape dispersal processes from fish biodiversity patterns

Dispersal patterns are recognized as a main determinant of biodiversity
structure, particularly in rivers. The dendritic organization of rivers,
waterflow direction, large distance immigrants from the outlet, and
fragmentation by dams combine to produce a complex dispersal scenario.
Unraveling the role, magnitude and spatial scale at which these different
dispersal sources determine metacommunity diversity is challenging and
demands a large amount of spatiotemporal information, which is rarely
available. Here, we incorporated alternative dispersal hypotheses in
coalescent and lottery models, contrasting their predictions with observed
fish diversity in the Negro River basin of Uruguay, South America.
Evidence from different models but supporting the same hypothesis was
combined, finding support for i) a dispersal constrained by the
riverscape—with no role for direct immigration from the metacommunity; ii)
an asymmetric neighbor dispersal, sharply decaying in upward but not in
downward river directions; iii) an outlet as a source of individuals that
affects diversity even at distant communities; and finally iv) a strong
effect of dams, indicating that fish diversity at the riverscape level is
now affected by dam constraints on individual movement. Both observed
alpha (r=0.58) and beta (r=0.54) diversity were well predicted by the
selected model, with a positive and a U-shaped association with
communities centrality. Process stochasticity—variation in diversity
metrics along realizations of the same assembly process— in alpha and beta
diversity were negatively and hump-shaped associated with communities
centrality. The ongoing fragmentation of rivers worldwide demands a
mechanistic understanding of the role of large-scale dispersal on
ecosystem diversity and stability. Selecting models and combining evidence
from different models allows the present research to advance on the
relative support for hypotheses with a comparatively limited amount of
empirical information, thus highlighting the potential of
theoretical-empirical approaches for identifying the mechanisms that shape
biodiversity.