Historical Diversification of a Terra-Firme Forest Bird Superspecies: A Phylogeographic Perspective on the Role of Different Hypotheses of Amazonian Diversification

Abstract

Abstract. Among those few hypotheses of Amazonian diversification amenable to falsification by phylogenetic and population genetics methods, three can be singled out because of their general application to vertebrates: the riverine barrier, the refuge, and the Miocene marine incursion hypotheses. I used phylogenetic and population genetics methods to reconstruct the diversification history of the upland (terra-firme) forest superspecies Xiphorhynchus spixii/elegans (Aves: Dendrocolaptidae) in Amazonia, and to evaluate predictions of the riverine barrier, refuge, and Miocene marine incursion hypotheses. Phylogeographic and population genetics analyses of the X. spixii/elegans superspecies indicated that the main prediction of the riverine barrier hypothesis (that sister lineages occur across major rivers) hold only for populations separated by ''clear-water'' rivers located on the Brazilian shield, in central and eastern Amazonia; in contrast, ''white-water'' rivers located in western Amazonia did not represent areas of primary divergence for populations of this superspecies. The main prediction derived from the refuge hypothesis (that populations of the X. spixii/elegans superspecies would show signs of past population bottlenecks and recent demographic expansions) was supported only for populations found in western Amazonia, where paleoecological data have failed to support past rainforest fragmentation and expansion of open vegetation types; conversely, populations from the eastern and central parts of Amazonia, where paleoecological data are consistent with an historical interplay between rainforest and open vegetation types, did not show population genetics attributes expected under the refuge hypothesis. Phylogeographic and population genetics data were consistent with the prediction made by the Miocene marine incursion hypothesis that populations of the X. spixii/elegans superspecies found on the Brazilian shield were older than populations from other parts of Amazonia. In contrast, the phylogeny obtained for lineages of this superspecies falsified the predicted monophyly of Brazilian shield populations, as postulated by the Miocene marine incursion hypothesis. In general, important predictions of both riverine barrier and Miocene marine incursion hypotheses were supported, indicating that they are not mutually exclusive; in fact, the data presented herein suggest that an interaction among geology, sea level changes, and hydrography created opportunities for cladogenesis in the X. spixii/elegans superspecies at different temporal and geographical scales.Key words. Aves, Amazonia, Miocene marine incursion hypothesis, phylogeography, population genetics, refuge hypothesis, riverine barrier hypothesis.Received March 10, 2003. Accepted February 10, 2004 The bird fauna of the Amazon lowlands in South America is the richest in the world, with over 1000 species, of which about 265 are endemic (Stotz et al. 1996;Nores 2000). As early as 1852, the British naturalist Alfred Russel Wallace put forward an evolutionary...

Avian gene trees, landscape evolution, and geology: towards a modern synthesis of Amazonian historical biogeography?

“…Despite those limitations, the reconstruction of the evolution of Tertiary and Quaternary deposits in Amazonia is of great relevance. This is because this time frame is thought to have witnessed the evolution of most of the modern Amazonian biodiversity, as indicated by several phylogeographic studies Hall and Harvey 2002;Marks et al 2002;Aleixo 2004Aleixo , 2006Armenta et al 2005;Cheviron et al 2005;Ribas et al 2005Ribas et al , 2006.…”

“…Of the four hypotheses of Amazonian diversification tested with species of the genus Xiphorhynchus, two had some of their important predictions supported: the riverine barrier and the Miocene marine incursion hypotheses (Aleixo 2002(Aleixo , 2004(Aleixo , 2006. Hence, these two hypotheses appeared not to be mutually exclusive and may together account for the diversification of the genus Xiphorhynchus in Amazonia at different temporal and geographical scales.…”

“…The pivotal role of recent studies of phylogeographic and population genetics in the critical evaluation of hypotheses of Amazonian diversification was further demonstrated by the series of papers on the avian genus Xiphorhynchus (Dendrocolaptidae); those studies tested predictions of four different hypotheses of Amazonian diversification with a broad, trans-Amazonian sampling regime (Aleixo 2002(Aleixo , 2004(Aleixo , 2006. Under the phylogeographic and population genetics frameworks, a test of the gradient (Endler 1982), riverine barrier (Gascon et al 2000), refuge (Haffer 1969), and Miocene marine incursion (Bates 2001) hypotheses of diversification would require a group of organisms with three main characteristics: high species richness, high ecological diversity, and widespread distribution.…”

“…The genus Xiphorhynchus fulfilled all the requirements above and provided an excellent model to investigate the historical diversification of Amazonian organisms: nine of the 14 currently recognized species of Xiphorhynchus occur throughout Amazonia, where they show remarkable levels of ecological as well as population differentiation (Marantz et al 2003). Therefore, phylogenetic and population genetics analyses of species in this genus provided important insights into the validity and generality of the four hypotheses of Amazonian diversification outlined above (Aleixo 2002(Aleixo , 2004(Aleixo , 2006.…”

The role of Pleistocene refugia and rivers in shaping gorilla genetic diversity in central Africa

“…In contrast, the riverine barrier hypothesis argues that tropical rivers limit species distributions (32,33) and shape intraspecific patterns of diversification (34,35). To date, support for this hypothesis is equivocal and depends heavily on the ecology and dispersal abilities of individual taxa.…”