Data from: Testing main Amazonian rivers as barriers across time and space within widespread taxa

Aim: Present Amazonian diversity patterns can result from many different
mechanisms and, consequently, the factors contributing to divergence
across regions and/or taxa may differ. Nevertheless, the river-barrier
hypothesis (RBH) is still widely invoked as a causal process in divergence
of Amazonian species. Here we use model-based phylogeographic analyses to
test the extent to which major Amazonian rivers act similarly as barriers
across time and space in two broadly distributed Amazonian taxa. Local:
Amazon rainforest. Taxon: The lizard Gonatodes humeralis
(Sphaerodactylidae) and the tree frog Dendropsophus leucophyllatus
(Hylidae). Methods: We obtained RADseq data for samples distributed across
main river barriers, representing main Areas of Endemism previously
proposed for the region. We conduct model-based phylogeographic and
genetic differentiation analyses across each population pair. Results:
Measures of genetic differentiation (based on FST calculated from genomic
data) show that all rivers are associated with significant genetic
differentiation. Parameters estimated under investigated divergence models
showed that divergence times for populations separated by each of the 11
bordering rivers were all fairly recent. The degree of differentiation
consistently varied between taxa and among rivers, which is not an
artifact of any corresponding difference in the genetic diversities of the
respective taxa, or to amounts of migration based on analyses of the
site-frequency-spectrum. Main conclusions: Taken together, our results
support a dispersal (rather than vicariance) history, without strong
evidence of congruence between these species and rivers. However, once a
species crossed a river, populations separated by each and every river
have remained isolated – in this sense, rivers act similarly as barriers
to any further gene flow. This result suggests differing degrees of
persistence and gives rise to the seeming contradiction that the
divergence process indeed varies across time, space, and species, even
though major Amazonian rivers have acted as secondary barriers to gene
flow in the focal taxa.