Evolution in the high-altitude Páramo ecosystem
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Date
29/06/2016Author
Gomez Gutierrez, Maria Camila
Metadata
Abstract
The Páramo ecosystem is the most diverse high-altitude ecosystem on Earth with
more than 4000 species of vascular plants. A naturally fragmented ecosystem, it also
houses one of the youngest and fastest evolving biota. In this thesis, molecular data
from the South American species of Oreobolus (Cyperaceae) and Páramo
representatives within the Melastomeae tribe (Melastomataceae) were used to
investigate the impact of Andean orogeny and recent climatic fluctuations on
diversification processes.
Chapter Two highlights the role of Andean uplift in the diversification of Páramo
species of Oreobolus as shown by their faster diversification rates compared to other
southern hemisphere species. It is suggested that Oreobolus may have reached South
America from Australia during the Pliocene through two independent long-distance
dispersal events to the northern and southern Andes. This strong north-south
geographic structure is evident in the species phylogeny. Chapter Three is a
phylogeographic study of the South American species of Oreobolus that reveals
complex relationships between and within species. Levels of haplotype sharing,
measures of genetic distinctiveness and recent divergence times point to incomplete
lineage sorting confounding species boundaries. Additionally, the role in species
diversification of the contraction and expansion of Páramo islands during the
climatic fluctuations of the Quaternary is supported by genetic data. Chapter Four
showed that colonisation of Páramo within the largely Neotropical Melastomeae tribe occurred repeatedly during the Pliocene. Species-poor Páramo lineages such as
Castratella may highlight a possible role for extinction in some taxa. In Chapter Four
I also suggested that frost adapted temperate lineages may have had an adaptative
advantage that may have contributed towards a greater number of species at higher
elevations.