A palaeobiogeographic model for biotic diversification within Amazonia over the past three million years

Abstract

Many hypotheses have been proposed to explain high species diversity in Amazonia, but few generalizations have emerged. In part, this has arisen from the scarcity of rigorous tests for mechanisms promoting speciation, and from major uncertainties about palaeogeographic events and their spatial and temporal associations with diversification. Here, we investigate the environmental history of Amazonia using a phylogenetic and biogeographic analysis of trumpeters (Aves: Psophia), which are represented by species in each of the vertebrate areas of endemism. Their relationships reveal an unforeseen 'complete' time-slice of Amazonian diversification over the past 3.0 Myr. We employ this temporally calibrated phylogeny to test competing palaeogeographic hypotheses. Our results are consistent with the establishment of the current Amazonian drainage system at approximately 3.0 -2.0 Ma and predict the temporal pattern of major river formation over Plio-Pleistocene times. We propose a palaeobiogeographic model for the last 3.0 Myr of Amazonian history that has implications for understanding patterns of endemism, the temporal history of Amazonian diversification and mechanisms promoting speciation. The history of Psophia, in combination with new geological evidence, provides the strongest direct evidence supporting a role for river dynamics in Amazonian diversification, and the absence of such a role for glacial climate cycles and refugia.

Prediction of phylogeographic endemism in an environmentally complex biome

“…We expect that more nuanced climatic analyses of other large complex biomes (e.g. sub-Saharan Africa [48], Amazonia [49] and Neotropical savannahs [50]) will help advance biodiversity prediction and conservation in tropical hotspots worldwide.…”

The Value of Including Intraspecific Measures of Biodiversity in Environmental impact Surveys is Highlighted by the Amazonian Brilliant-Thighed Frog (Allobates Femoralis)

“…In particular, the damming of rivers to generate hydroelectric power alters large areas through flooding and disruption of seasonal water flows downstream of reservoirs [7]. The value of conserving watershed ecosystems is underscored by research demonstrating that Amazonian inter-fluvial regions are known to house unique components of biodiversity [9][10].…”

Is the largest river valley west of the Andes a driver of diversification in Neotropical lowland birds?

“…In fact, 2 of the 4 species evaluated in our study (X. susurrans and M. oleagineus) have been shown to be able to potentially overcome water barriers .300 m wide (Moore et al 2008), and previous work has shown that Amazonian rivers with similar widths to the Magdalena do not represent barriers for other species in the genus Xiphorhynchus (Aleixo 2004). In contrast, examples of differentiation across other Neotropical rivers often involve species with limited dispersal abilities (e.g., trumpeters: Ribas et al 2012;antbirds: Maldonado-Coelho et al 2013). Work on species that occur in the MRV and that have lower dispersal abilities (e.g., some members of the Thamnophilidae or Troglodytidae) is necessary to determine whether the Magdalena River may indeed act as a geographic barrier for some birds (Hayes andSewlal 2004, Moore et al 2008).…”

“…Inter-Andean valleys, rivers of the Amazon Basin, and the Andean mountain range are all important barriers to gene flow responsible for isolation and population differentiation in allopatry in Neotropical birds (e.g., Aleixo 2004, Cheviron et al 2005, Ribas et al 2012, Gutiérrez-Pinto et al 2012, Maldonado-Coelho et al 2013, Smith et al 2014, Fernandes et al 2014. A less-studied mechanism of population differentiation in Neotropical birds is environmental variation, which might play a role in restricting gene flow among populations (Rundle and Nosil 2005, Peterson and Nyári 2008, Nosil and Harmon 2009, Rodriguez et al 2015.…”