@ARTICLE{TreeBASE2Ref21953, author = {Nicolai M. N?rk and Charlotte Scheriau and Santiago Madri??n}, title = {Explosive radiation in p?ramo Hypericum ? rates of diversification among New World lineages}, year = {2013}, keywords = {Adaptive Radiation, Andes Mountains, diversification, Hypericum, rDNA ITS phylogenetics, Neotropics, P?ramos}, doi = {10.3389/fgene.2013.00175}, url = {http://www.frontiersin.org/Evolutionary_and_Population_Genetics/10.3389/fgene.2013.00175/abstract}, pmid = {24062764}, journal = {Frontiers in Genetics ? Evolutionary and Population Genetics. Special volume: Effects of mountain formation and uplift on biological diversity}, volume = {4}, number = {175}, pages = {}, abstract = {High-elevation Andean grasslands, the p?ramos, ranging from ca. 2800 m to the snow line, harbor one of the fastest evolving biomes worldwide since their appearance in the northern Andes 3?5 million years (Ma) ago. Hypericum (St. John?s worth) has with over 63% of its Neotropical species a center of diversity in these high Mountain ecosystems. Using nuclear rDNA internal transcribed spacer (ITS) sequences of a broad sample of South American Hypericum species we investigate phylogenetic patterns, estimate divergence times, and provide the first insights into diversification rates within the genus in the Neotropics. Two lineages appear to have independently dispersed into South America around 3.5 Ma ago, one of which has radiated in the p?ramos (Hypericum section Brathys). We find strong support for the paraphyly of H. sect. Trigynobrathys, several species of which group within H. sect. Brathys, while others are found in temperate lowland South America (H. sect. Trigynobrathys s.str.). All p?ramo species of Hypericum group in one clade. Within these p?ramo Hypericum species unparalleled phenotypic evolution has taken place (life forms from arborescent to prostrate shrubs) evidently in a short time frame. We hypothesize multiple mechanisms to be responsible for the low differentiation in the ITS region contrary to the high morphological diversity found in Hypericum in the p?ramo. Amongst these may be ongoing hybridization and incomplete lineage sorting, as well as the putative adaptive radiation, which may explain the contrast between phenotypic diversity and the close genetic relationships.} }

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