Amazon floodplains is a mosaic of environments who occupy more than 10% of basin
and harbor countless species of animals and plants. In this context, the associeted
avifauna exhibit different degrees of dependence related to use of microhabitats. Despite
its ecological importance, the organisms’ population dynamics that use these
environments are not well known, as well as the historical mechanisms that influenced
the formation of these landscapes. Thus, this study evaluated the population dynamics
of four forest birds species specialized in the Amazon floodplains use. Among these, were
evaluated a generalist specie in the floodplain use (Hypocnemoides melanopogon) and
three species that use preferably fluvial islands (Myrmotherula assimilis, Myrmoborus
lugubris and Thamnophilus nigrocinereus), environments arranged discretely in
landscape. When considering archipelagos situated in lower Negro River, despite
evidences of gene flow between islands, subtle signals indicate that genetic diversity is
heterogeneously distributed across the landscape. In a broader geographic scale,
lineages of birds specialists of insular environments exhibited distinctions between Negro
and other great rivers of Amazon. These results contrast with other studies that indicated
no genetic structure in specialized birds in the amazon’s floodplains. It should be noted
that such response was not observed in the generalist specie of flooded areas,
suggesting that the organisms’ ecological characteristics can influence genetic diversity
in these habitats. The temporal congruence of divergences between lineages of Negro
and Solimões are evidences that paleoclimatic and geologic process related to the
formation of landscape in recent past (Pleistocene) were possibly responsible by the
current organization of these species. Finally, the species studied does not showed
remarkable signals of population expansion, a similar result to that achieved for other
floodplains’ birds, but are contrasting to those obtained in lowland (Terra Firme)
organisms. This answer can be an idicative of constant avaliability of floodplains during
the transition Pleistocene/Holocene.
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