Doctor of Philosophy (PhD)


Biological Sciences

Document Type



Amazonia has the largest and most biodiverse tropical forest on the planet. However, the distributions of its species are still poorly understood, even for well-studied vertebrates such as birds. Available distribution maps for Amazonian birds often lack accuracy in delimiting the area where species occur. Existing distributional information for Amazonian birds is often limited to species-level level taxonomy, even though many Amazonian bird subspecies represent biological species. Here, I investigate the geographic distributions of 4,148 bird taxa (species and subspecies) using museum scientific specimens as the primary source of data. To build the data base I use more than 600,000 specimen records as point localities. In Chapter 2, I revised locality information from museum specimens and the literature to draw the distributional ranges for each taxon as range polygons. I then used the distributional ranges to define Amazonian zoogeographic regions based on distributional patterns. I found that maps of Amazonian bird distributions at the subspecies level better capture the regional diversity of birds in Amazonia. This new distributional dataset of Amazonian birds allows biodiversity studies (e.g. macroecology, evolution, conservation) to be conducted at the subspecies level. This will facilitate biogeographic, ecological, evolutionary, and conservation research on birds in the most diverse region in the world. In Chapter 3, I used the database to map avian contact zones throughout Amazonia and its adjoining regions. By grouping avian taxa into phylogenetically related groups, I was able to map regions where close related taxa replace each other, often at hybrid zones. I found groups of taxon turnovers at the same geographic location. These suture zones were found throughout the entire Amazonian region, but most were associated with large rivers. In lowland Amazonia, rivers coincide with the location of most suture zones, as rivers are clear but often permeable dispersal barriers to birds in this region of the world. My results in Chapter 3 corroborated the observation that Amazonian rivers tend to have a diminished barrier effect close to their headwaters. The conservation status of 3,320 bird taxa was the focus of Chapter 4. I used the range polygons created in Chapter 2 as a proxy for the extent of occurrence (EOO) of Amazonian birds. I integrated the EOO of each taxon with their distributional records (locality points) to generate models of environmental suitability in both current and future climatic scenarios. I also incorporate current and future deforestation information into the different projected scenarios. Based on the size of distributional area of each taxon in each scenario modelled, I classified 3,320 taxa in one of the IUCN’s Red-List categories using the criterium B1 (i.e. geographic distribution). I found that avian taxa from all Amazonian regions will be impacted by future environmental conditions, but to different degrees. Birds ranging along the eastern slopes of the Andes will face the greatest reduction in their range. In south and east Amazonia the high rates of deforestation combined with more extreme future climate conditions will heavily diminish distributions. My conclusions based on subspecific taxa provide a finer granularity to current IUCN conservation classifications.



Committee Chair

Brumfield, Robb T.



Available for download on Monday, December 08, 2025