UC Berkeley

The abundant floristic diversity of the Amazon rain forest has been a source of fascination for naturalists throughout history. Efforts to understand floristic patterns in this region have haven taken a wide range of interdisciplinary approaches, including taxonomic and ecological studies, historical biogeography, and evolutionary biology. These approaches have provided insights into the niches of various plants, their biogeographic history, and their cultural significance. Much work remains to be done to describe the genetic and phenotypic variation of Amazonian species and to uncover the mechanisms underlying coexistence in these extraordinarily diverse rainforests, which can support more than a hundred tree species within a single hectare.

In this dissertation, I report on an iconic and widespread palm tree throughout Amazonia, Oenocarpus bataua, which has a long history of use and association with Indigenous and local peoples of the region. I use both ecological and evolutionary perspectives to add to the growing body of literature around floristic biodiversity in the Amazon, using this species as a study system. O. bataua is a part of a small subset of hyperdominant trees in the Amazon, making it common in the landscape, yet it has not been subject to many in-depth ecological experiments or genomic studies.

In chapter 1, I report my findings from a manipulative field experiment to explore possible mechanisms that allow O. bataua to be locally dominant in the Allpahuayo-Mishana National Reserve in Iquitos, Peru. Specifically, I look at the effects of seed and seedling density and distance from adult trees on germination and survival. I found that seeds placed at an increased distance from adult trees had significantly higher germination rates than those placed underneath adult trees. I postulate that O. bataua’s effective dispersal, which has been well documented, is related to its success as a hyperdominant tree.

In chapter 2, I present a leaf transcriptome assembly and annotation for Oenocarpus bataua and identify a suite of genes involved in the production of fatty acids. I go on to compare the diversity of these genes with those of other commercial palm crops and provide additional information for O. bataua to be considered as a promising alternative source of commercial oil.

In chapter 3, I developed a set of molecular probes based on the transcriptome described in chapter 2 to study the population structure of Oenocarpus bataua in Northwestern South America in more detail. I elucidated the genetic patterns observed from populations on either side of the Andes mountain range and suggest that its arrival west of the Andes occurred after the mountains had reached significant height, and this colonization event was facilitated by the great dispersal ability of O. bataua.

Collectively, this dissertation provides insight into the ecological and evolutionary mechanisms contributing to the hyperdominance, genetic diversity, and biogeographic patterns of Oenocarpus bataua. I report various lines of evidence that allude to the importance of dispersal in the ecology of this iconic palm and speculate that this may be a common trait among hyperdominant trees. Furthermore, this project serves as a resource for both a greater understanding of tropical ecology as well as contributing to knowledge relevant to alternative sustainable forest products development.