Biological Dynamics of Forest Fragments Project, Instituto Nacional de Pesquisas de Amazonica, C.P. 478, 6901–970 Manaus, Amazonas, Brazil.
Patterns of Genetic Population Differentiation in Four Species of Amazonian Frogs: A Test of the Riverine Barrier Hypothesis1
Article first published online: 15 MAR 2006
Volume 30, Issue 1, pages 104–119, March 1998
How to Cite
Gascon, C., Lougheed, S. C. and Bogart, J. P. (1998), Patterns of Genetic Population Differentiation in Four Species of Amazonian Frogs: A Test of the Riverine Barrier Hypothesis. Biotropica, 30: 104–119. doi: 10.1111/j.1744-7429.1998.tb00373.x
Received 27 September 1995; revision accepted 1 July 1996.
- Issue published online: 15 MAR 2006
- Article first published online: 15 MAR 2006
- riverine barrier hypothesis
Patterns and levels of allozyme variation among populations of Amazonian frogs were used to test the riverine barrier hypothesis of species differentiation. Two frog species were sampled from each of the two main forest habitats on both banks of the Juruá River in the southwestern Brazilian Amazon Basin at various points along its course to contrast different barrier strengths. Scarthyla ostinodactyla and Scinax rubra were sampled from flooded forest (varzea), and Physalaemus petersi and Epipedobates femoralis from non-flooded forest (terra firme). All species showed high levels of within-population genetic variation. Average Nei's (1978) and Rogers’ (1972) genetic distances between sampled sites for all species were high indicating substantial among-population differentiation. The observation of low gene flow between sampled sites within species was further substantiated with Slatkin's (1993) M̂ analyses. Randomization tests suggested that there was some population structure at a few assayed polymorphic loci that was consistent with the riverine barrier hypothesis. However, it was apparent from the raw allozyme frequency data that these results were largely driven by substantial differentiation at one or a few collecting localities rather than by basin-wide patterns of riverine differentiation. Phenograms using genetic distance matrices supported this interpretation. Patterns of geographic variation are probably more consistent with the idea of this region being a zone of secondary contact.