Molecular Phylogenetics and Evolution 44 (2007) 825–837 www.elsevier.com/locate/ympev 1055-7903/$ - see front matter  2007 Elsevier Inc. All rights reserved. doi:10.1016/j.ympev.2007.01.012 Tests of biogeographic hypotheses for diversiWcation in the Amazonian forest frog, Physalaemus petersi W. Chris Funk a,¤,1 , Janalee P. Caldwell b , Colin E. Peden a , José M. Padial c , Ignacio De la Riva d , David C. Cannatella a a Section of Integrative Biology, University of Texas, 1 University Station C0930, Austin, TX 78712, USA b Sam Noble Oklahoma Museum of Natural History, Department of Zoology, University of Oklahoma, 2401 Chautauqua Ave., Norman, OK 73032, USA c Museo de Historia Natural Noel KempV Mercado, Area de Zoología, P.O. Box 2489, Santa Cruz de Sierra, Bolivia d Museo de Ciencias Naturales-CSIC, C/José Gutierrez Abascal 2, 28006 Madrid, Spain Received 15 September 2006; revised 17 January 2007; accepted 25 January 2007 Available online 15 February 2007 Abstract Several hypotheses have been proposed to explain the biogeographic processes that generate the high species richness of the Amazon basin. We tested two of them in a terra Wrme (upland) forest frog species, Physalaemus petersi: (1) the riverine barrier hypothesis; and (2) the elevational gradient hypothesis. Mitochondrial DNA sequence data (2.4 kb) from the 12S, 16S, and intervening valine tRNA genes were obtained from 65 P. petersi individuals and 4 outgroup taxa and analyzed with a combination of phylogenetic and population genetic approaches. Moderate support for the riverine barrier hypothesis was found for one of the three rivers examined, but little evi- dence was found for the elevational gradient hypothesis. Phylogenetic analyses revealed that high levels of sequence divergence (an aver- age of 4.57–4.79%) separate three well-supported clades from the northwestern, southwestern, and eastern Amazon. Strong evidence for recent population expansion in P. petersi in the southwestern region of the Amazon basin was also uncovered.  2007 Elsevier Inc. All rights reserved. Keywords: Physalaemus; Frog; Amazon basin; Mitochondrial DNA; Phylogeography; Speciation; Population expansion 1. Introduction The processes that generate the high species richness of the Amazon basin have fascinated evolutionary biologists and naturalists since the 19th century (Bates, 1863; von Humboldt, 1808; Wallace, 1853). Historically, investiga- tions of these processes relied primarily on distributional data of extant taxa (e.g., HaVer, 1969; Wallace, 1852). How- ever, molecular phylogeographic studies of populations and recently diverged species (e.g., Aleixo, 2004; Cheviron et al., 2005; da Silva and Patton, 1993; Glor et al., 2001; HoVman and Baker, 2003; Kronauer et al., 2005; Lessa et al., 2003; Lougheed et al., 1999; Lovette, 2004; Marks et al., 2002; Patton et al., 2000; Zamudio and Greene, 1997), coupled with hypothesis testing, promise to illuminate our understanding of speciation processes in the Amazon basin. Several biogeographic mechanisms have been proposed to explain diversiWcation in the Amazon, including allo- patric speciation via riverine barriers (Wallace, 1852), for- est refugia (HaVer, 1969, 1997), marine incursions (Nores, 1999; Webb, 1995), historic mountain ridges (Räsänan et al., 1990), or climatic disturbance (Bush, 1994; Colinv- aux et al., 1996; Colinvaux, 1998), as well as parapatric speciation caused by divergent selection across ecological gradients (Endler, 1977). Some sites in the Amazon Basin have the highest known species richness of amphibians (Duellman, 1978, 1988, 1999), yet studies of amphibian speciation in an explicit phylogeographic framework have just started (Chek et al., 2001; Lougheed et al., 1999; Symula et al., 2003). * Corresponding author. Fax: +1 541 758 8806. E-mail address: cfunk@usgs.gov (W.C. Funk). 1 Present address: USGS Forest and Rangeland Ecosystem Science Cen- ter, 3200 SW JeVerson Way, Corvallis, OR 97331, USA. brought to you by CORE View metadata, citation and similar papers at core.ac.uk provided by Digital.CSIC