02248nas a2200157   4500008004100000020001600041245010900057210006900166300000800235490000600243520163400249100002301883700002401906700002501930856013501955       2013                        eng d  a- 1664-802100aExplosive radiation in high Andean <i>Hypericum</i>– Rates of diversification among New World lineages0 aExplosive radiation in high Andean iHypericumi Rates of diversif  a1750 v43 a<p>The p&aacute;ramos, high-elevation Andean grasslands ranging from ca. 2800m to the snow line, harbor one of the fastest evolving biomes worldwide since their appearance in the northern Andes 3&ndash;5 million years (Ma) ago. Hypericum (St. John&rsquo;s wort), with over 65% of its Neotropical species, has a center of diversity in these high Mountain ecosystems. Using nuclear rDNA internal transcribed spacer (ITS) sequences of a broad sample of New World 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&aacute;ramos (Brathys). We find strong support for the polyphyly of section Trigynobrathys, several species of which group within Brathys, while others are found in temperate lowland South America (Trigynobrathys s.str.). All p&aacute;ramo species of Hypericum group in one clade. Within these p&aacute;ramo Hypericum species enormous 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&aacute;ramos. Amongst these may be ongoing hybridization and incomplete lineage sorting, as well as the putative adaptive radiation, which can explain the contrast between phenotypic diversity and the close phylogenetic relationships.</p>
1 aNürk, Nicolai, M.1 aScheriau, Charlotte1 aMadriñán, Santiago  uhttp://www.frontiersin.org/Journal/Abstract.aspx?s=1254&name=evolutionary_and_population_genetics&ART_DOI=10.3389/fgene.2013.00175