Population dynamics of Amazonian floodplain forest species support spatial variation on genetic diversity but not range expansions through time

Aim The distribution and connectivity of floodplain environments along major Amazonian rivers changed considerably over time following physiographic and climatic events. However, how historical alteration in floodplain habitats affected endemic species' demography and diversification is not fully understood. We tested if historical demographic changes of populations occurring on the floodplains of a major Amazon Basin tributary could be associated with range expansions from upper and middle sections of the river, following the establishment of widespread river-created environments during the Late Pleistocene and Holocene. Location Solimoes River, Western Amazon, South America. Taxon Myrmoborus lugubris, Thamnophilus cryptoleucus and Myrmotherula assimilis. Methods We explored spatial patterns of genetic diversity and connectivity among 13 sampled localities using thousands of UltraConserved Elements. We used a total of 73 individuals of three species with populations restricted to the Solimoes River. Range expansions were tested with spatial explicit methods designed to capture variations in allele frequency over space. To test whether the occupation of dynamic habitats could predict spatial patterns of genetic diversity, we quantified habitat preference for the three analysed species by creating a metric of habitat dynamicity over time. Results We found considerable variation in the spatial distribution of the genetic diversity between studied taxa rejecting shared population range expansions related to historical regionalized changes in habitat availability. Species with higher levels of specialization to dynamic environments have a more heterogeneous distribution of genetic diversity and reduced levels of gene flow across space. Main conclusions The demographic expansions along the Solimoes River might be linked to spatially homogeneous oscillation in the distribution of floodplain environments, promoting effective population size changes but not range expansion. Habitat specificity might be a good predictor of population connectivity along the Amazonian floodplains. (AU)