Geophylogeny—Merging Views of Evolution and Migration

The images in this display depict an exploration of a “geophylogenetic” visualization capability to promote understanding of phylogenetic evolution and geographic spread. The simultaneous visualization of phylogenetic relationships and spatial relationships has clear applications to epidemiology and forensics. The images shown are preliminary. They were rendered using the ArcScene application within ArcGIS 3D Analyst from a supplied phylogeny tree and geolocated strain positions.

Three examples are depicted. Two are from the worldwide Bacillus anthracis data supplied by Paul Jackson and Paul Keim of Northern Arizona University. Example 1 is a visualization of a subset of the data (the A1.a and A1.b clades). In the image, one sees how the orange A1.a and green A1.b subtrees join. Here the geography confirms the phylogeny and indicates a possible location for the inferred common ancestor of these clades. The numbered locations represent geolocated strains. Matching strains are geographically connected.

Example 2 depicts the global Bacillus anthracis distribution. Example 3 is a visualization of preliminary data on severe acute respiratory syndrome (SARS). The current work employs a simple algorithm. Strains are plotted at their observed locations. Ancestors are plotted at a height calculated by the phylogenetic distance and at a geographical location given by the centroid of the descendant’s positions.

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