The original version of this Article contained several errors. In Figure 3a, both axes were incorrectly labelled as "PC2". The correct x axis label is "PC1". The present affiliation of Warren E Johnson with the Walter Reed Biosystematics Unit, Smithsonian Institution, was inadvertently omitted. The following statement was also omitted from the Acknowledgements: “Portions of this manuscript were prepared while W.E.J held a National Research Council Research Associateship Award at the Walter Reed Army Institute of Research and the published material reflects the views of the authors and should not be construed to represent those of the Department of the Army or the Department of Defense.” The initials “W.J” in the Author Contributions statement should have been listed as “W.E.J”. These errors have now been corrected in both the PDF and HTML versions of the Article.