Evolutionary patterns and processes of the high Andean genera Demosthenesia, Pellegrinia, Polyclita, Rusbya, and Siphonandra (Vaccinieae: Ericaceae)




Ortiz Valencia, Edgardo Manuel Martín

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The Andean uplift is arguably the most important geologic event that led to the diversification of the richest biota in the planet. By the end of the Miocene, the Andes reached almost half their current elevation and their eastern slopes intercepted, condensed, and precipitated enough westward-moving moist air from the Amazon to cause the formation of montane forests. Later, climatic oscillations during the Pleistocene heavily affected the distribution of upper montane forests. Today, the upper belt of these forests, also known as cloud forest, possesses the highest levels of endemism in the world, however, the processes that drove this diversification are still poorly understood. To investigate these processes, I selected the blueberry tribe, Vaccinieae, that contains ~1,760 species mostly concentrated in the Neotropics and particularly abundant in the montane forests of the eastern Andean slopes. In chapter 1, I focus on a group of five endemic genera (Demosthenesia, Pellegrinia, Polyclita, Rusbya, and Siphonandra) that inhabit the cloud forest up to timberline at ~3000-3500 masl. I investigate if they share a single or multiple evolutionary origins by constructing the largest and most robust time-calibrated phylogeny of the tribe to date and performing diversification and historical biogeographic analyses. In chapter 2, I use a phylogenomic approach seeking to further resolve the relationships of the most recently diverged groups, Demosthenesia and Rusbya. Finally, in chapter 3, I explore the effects of Pleistocene climatic oscillations on the present geographic and genetic structure of the widespread blueberry species Demosthenesia mandonii, and attempt to locate areas that might have served as Pleistocene refugia. My results indicate that the five genera do not share a single origin, however their divergence dates are contemporaneous at ~6 Ma. At a larger scale, the Neotropical blueberries have multiple evolutionary origins, with a main radiation influenced by both the uplift of the Andes and Cenozoic temperatures. Lastly, the population analysis of D. mandonii, suggests a severe contraction of its range during the last glacial maximum followed by re-expansion towards the present, this species most likely survived the las glaciation in a single Pleistocene refugium located in the Urubamba valley (Cusco, Peru).



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