A digital base map for studying the Neotropical flora
Authors: Bletter Nat , Janovec John , Brosi Berry , Daly Douglas C. 
Published: February 2008

Despite advances in Geographic Information Systems (GIS) and remote–sensing technology and software, to date most systematists and other botanists working on the Neotropical flora, particularly on the monographic series Flora Neotropica, have used hard–copy maps. These maps make it possible to see basic distribution patterns, but they are highly inaccurate, and the fact that the data are not compiled in digital form means that it is difficult or impossible to retrieve the metadata (i.e., the collection data and attributes of the specimen(s) associated with each point on the map), select and combine distribution datasets for various organisms, perform spatial statistics on the distributions, or overlay species distributions onto maps of soils, climate, and other environmental variables. In an effort to help modernize Neotropical plant studies and make GIS more accessible to botanists, we have developed a digital base map of the Americas with multiple registered map layers that can be superimposed in any combination and can be used to easily create digital distribution maps from collection lists for dissemination and analysis. This base map, freely available to botanists and systematists, was made using ArcView® GIS. Several of the layers were derived from Environmental Systems Research Institute (ESRI) datasets (ArcWorld®, ArcAtlas®, Digital Chart of the World®). For a basic version of this system we obtained additional datasets on vegetation and soils (Woods Hole Research Center), elevation (U.S. Geological Survey), and EcoRegions (World Wildlife Fund); for our own projects, we have added layers from a number of additional sources and more appropriate in scale for Amazonia and the state of Acre, Brazil. The layers are being expanded upon as new datasets become available, and we are actively seeking additional sets from other sources, including geographical institutes in individual Neotropical countries. This system makes it possible to carry out a number of rather elegant analyses and visualizations, including the following: (1) plot the distributions of species and use the overlays to easily visualize coincidence of distribution patterns with geographic and environmental features; (2) map values for morphological characters onto the distribution points in order to examine character variation over the range of the species (e.g., plotting leaf size to see latitudinal or longitudinal patterns); (3) quantitatively analyze spatial statistics (e.g., examining the relationship between fruit size and rainfall); and (4) vastly increase the agility and versatility of historical biogeography techniques. Though any botanist adept at using GIS theoretically could conduct these analyses, the Americas Base Map assembles a disparate set of high–quality, botanically relevant environmental and geographic data in one place and provides instructions that obviate the need for deep expertise in GIS. This dramatically improves access to relevant geospatial data for botanists, especially in the developing world, and should serve to expand the use of GIS in plant biogeography. We anticipate that this multifaceted approach to mapping species distributions will facilitate the work of systematists and floristicians, and that it will help Neotropical plant geography to progress from conjecture to testable hypotheses. The Americas Base Map may be utilized by any botanist affiliated with a non–profit institution and with access to ArcView®, and it is available on CD by request.