Wednesday, October 12, 2016

[Herpetology • 2016] Evolution in the South American ‘Lost World’: Insights from Multilocus Phylogeography of Stefanias (Anura, Hemiphractidae, Stefania)


Figure 1. (a) Map of Pantepui and its location within South America (inset). (b) Aerial view of the northern part of Mount Roraima (the Prow), Guyana, showing typical tepuian sheer cliffs and lower forested slopes. Photo:  D. Bruce Means
Figure 2. Graphical representation of the historical biogeography of Stefania in eastern Pantepui.

Abstract
Aim
To investigate the influence of tepuian geomorphology on species diversification in the Pantepui biogeographical region based on the phylogenetic relationships and divergence times of tepui-endemic clades of stefania frogs (Stefania, Hemiphractidae).

Location
The ‘tepuis’ and uplands/lowlands of the Pantepui biogeographical region of northern South America, one of the least accessible and least studied areas in the world.

Methods
Two mitochondrial and two nuclear DNA sequences from 60 individuals of Stefania from 24 localities in Pantepui were employed to infer phylogenetic affinities and estimate divergence times within the genus using both concatenation and species tree analyses. Ancestral areas were inferred using multiple models in a common likelihood framework.

Results
Phylogenetic analyses revealed high diversity in the genus Stefania with 10 candidate species in the Eastern Pantepui District. Four strongly supported clades are recovered in the area, one being exclusively composed of microendemics on isolated tepui summits. Biogeographical analyses suggest episodes of fragmentation of widespread tepuian ancestors from the onset of diversification of the genus, estimated in the Oligocene (c. 26 Ma), therefore suggesting a neglected vicariant model of Pantepui evolution, the Plateau Theory.

Main conclusions
Although our results suggest that vicariance played an important role in the diversification of Stefania, speciation in Pantepui followed an intricate pattern implying multiple nonexclusive processes. Vicariance and dispersal likely influenced diversification patterns of the Pantepui fauna, possibly according to the following sequence: (1) Cenozoic vicariance; (2) reorganization of species diversity due to periods of climatic instability; (3) recent invasions (Pleistocene) of widespread upland taxa.

Keywords: ancestral areas, anuran, dispersal, divergence times, frog, molecular phylogenetics, phylogeography, tepui, Venezuela, vicariance


Philippe J. R. Kok, Valerio G. Russo, Sebastian Ratz, D. Bruce Means, Ross D. MacCulloch, Amy Lathrop, Fabien Aubret and Franky Bossuyt. 2016. Evolution in the South American ‘Lost World’: Insights from Multilocus Phylogeography of Stefanias (Anura, Hemiphractidae, Stefania).  Journal of Biogeography. DOI: 10.1111/jbi.12860 

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