Among the hypothesized causes of biogeographic diversity are spatial and temporal variability in ecological conditions, such as climate, soil type, topography, competition among species, dispersal abilities of species, and historical climate changes. Additional complexity is contributed by human influences, including hunting, agriculture, and forestry. This doctoral dissertation research project will use standardized biological surveys across variable forest landscapes in the western Amazon basin to test the relative influence of these different factors on the geographical distribution of bird species assemblages. Measurable proxies used to test hypothesized causes of diversity include plant species composition, structural characteristics of the forest, elevation, location relative to major dispersal barriers (rivers) and hypothesized biogeographic zones (ecoregions), distances among sites, and accessibility relative to local human settlements and regional markets. The relative influence of plant species composition vs. the physical structure of vegetation is of particular interest for investigating habitat selection in birds. Analysis of associations at local, landscape, and regional scales will test effects of spatial scale. Spatial patterns will be investigated for all bird species together and for subsets of species. Examining ecologically and phylogenetically defined species groups will allow the identification of diversity in the ways different groups may respond to particular influences. For example, hunting pressure is expected to disproportionately affect large-bodied species. If particular species groups reflect patterns observed more generally in the bird community, those groups may be identified as indicator groups that can improve the efficiency of future survey work. Results of this study may identify more complex situations in which different groups of bird species respond at different spatial scales to different factors. Nonetheless, the identification of robust associations between bird species assemblage distributions and explanatory factors may allow the inference of patterns of community distinctiveness across wide areas, subject to validation with new survey data.
Basic information about the spatial distribution of biodiversity at landscape and regional scales is relatively scarce in the Amazon basin, and the biogeographic classification of landscapes is therefore a basic goal of this research. Furthermore, the integrative approach taken by this research will help advance biogeographic theory by quantitatively assessing the biodiversity status of particular places as outcomes of multiple cultural and natural processes operating at multiple spatial scales. The production and integration of multiple forms of biogeographic information also can play a key role in the development of sustainable cultural landscapes, because biologically distinctive places have distinctive conservation values and resource use potentials. Geographic information that informs conservation and development planning is of particular value in areas where growth and landscape change are occurring rapidly, such as this project's study area surrounding the city of Iquitos in the Peruvian Amazon. As a Doctoral Dissertation Research Improvement award, this award also will provide support to enable a promising student to establish a strong independent research career.
