FIGURE 1. Maps of freshwater fish diversity and AARP in the MMRS.
From the following article:
Neutral metacommunity models predict fish diversity patterns in Mississippi–Missouri basin
Rachata Muneepeerakul, Enrico Bertuzzo, Heather J. Lynch, William F. Fagan, Andrea Rinaldo & Ignacio Rodriguez-Iturbe
Nature 453, 220-222(8 May 2008)
doi:10.1038/nature06813
a, Local species richness (LSR), or 
diversity, of the freshwater fish in each DTA (that is, at the USGS HUC8 scale; see the text) of the MMRS. b, The AARP of the MMRS.