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Research Project: Genetic Characterization, Genetic Improvement, and Best Horticultural Management Practices for Subtropical/Tropical Ornamental Germplasm

Location: Subtropical Horticulture Research

Title: Contrasting andean geodynamics drive evolution of lowland taxa in western Amazonia

Author
item Roncal, Julissa - Memorial University Of Newfounland
item Couderc, Marie - Institut De Recherche En Sciencies De La Sante
item Baby, Patrice - Universite De Tours
item Kahn, Francis - Universidad Nacional De Cordoba
item Millan, Betty - Universidad Nacional De Cordoba
item Meerow, Alan
item Pintaud, Jean-christophe - Institut De Recherche En Sciencies De La Sante

Submitted to: Journal of Biogeography
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 7/28/2014
Publication Date: 3/11/2015
Citation: Roncal, J., Couderc, M., Baby, P., Kahn, F., Millan, B., Meerow, A.W., Pintaud, J. 2015. Contrasting andean geodynamics drive evolution of lowland taxa in western Amazonia. Journal of Biogeography. DOI: 10.1111/jbi.12518.

Interpretive Summary: The Nazca plate subduction and the eastward Andean orogenic wedge propagation in western Amazonia caused the retreat of the aquatic Pebas system and the formation of arches or ridges that influenced the modern configuration of the upper Amazon drainage. These palaeogeographical changes in topographic relief and river dynamics are thought to have influenced the diversification of biota through vicariance. We used a palm lineage of 15 species (Astrocaryum sect. Huicungo:Arecaceae) to test this hypothesis that had received contrasting empirical evidence. A total of 78 palm individuals were collected in the field, for which five chloroplast and two nuclear DNA fragments were sequenced. We reconstructed a total evidence Bayesian phylogeny with diversification times to detect phylogeographic breaks. We used a population genetic approach to test for past demographic expansions, and a Bayesian phylogeographic spatial diffusion approach to propose a model of colonization and diversification in western Amazonia. We found a phylogeographic break at ca. 5°S, defined by two main clades that diversified ca. 6.7 and 7.3 Ma in the rising sub-Andean foothills of central Peru, and in the subsiding northern Amazonian foreland basin, respectively. These dates coincided with sub-Andean foothills uplift around 9 Ma, and the transcontinental modern drainage and sedimentation plain of the northern Amazonian foreland basin, which started around 5 Ma. We found evidence of past ancestral population expansion into western Amazonia, and no clear genetic differentiation imposed by river barriers or arches. Our results support the role of dispersal of a group of palm trees into western Amazonia, followed by speciation within two areas of contrasting geological activity, tectonic uplift versus subsidence, in the last eight Myr, to explain the origin of lowland tropical forest plants.

Technical Abstract: Using a palm lineage of 15 species (Astrocaryum sect. Huicungo), we tested an hypothesis that past geologic events in western Amazonia influenced the modern configuration of the upper Amazon drainage and thus diversification and distribution of these palsm, which found only in this region. The changes in topographic relief and river dynamics are thought to have influenced the diversification of plants and animals through genetic isolation. A total of 78 palm individuals were collected in the field, for which five chloroplast and two nuclear DNA fragments were sequenced. We estimated diversification times and used a population genetic approach to test for past population expansions, and proposed a model of colonization and diversification in western Amazonia. We found that a significant break at around 5°S latitude that defined two main clusters of species that diversified about 6.7 and 7.3 million years ago in the rising sub-Andean foothills of central Peru, and in the subsiding northern Amazonian foreland basin, respectively. These dates coincided with sub-Andean foothills uplift around 9 million years ago, and the modern drainage and sedimentation plain of the northern Amazonian foreland basin, which started around 5 million years ago. We found evidence of past ancestral population expansion into western Amazonia, and no clear genetic differentiation imposed by river barriers or topographic arches. Our results support the role of dispersal of a group of palm trees into western Amazonia, followed by speciation within two areas of contrasting geological activity in the last eight million years ago to explain the origin of lowland tropical forest plants.