Figure 2. . Phylogeny of the North American arenaviruses based on a neighbor-joining analysis of nucleocapsid protein amino acid sequence data. Distances and groupings were determined by using the gamma distance algorithm (alpha = 2). Branch lengths are proportional to the gamma distance between amino acid sequences. Numbers indicate the percentage of 500 bootstrap replicates that supported each labeled interior branch. WWA virus prototype strain AV 9310135 is in bold type. Nmex = Neotoma mexicana, Nalb = N. albigula, Ncin = N. cinerea, Nmic = N. micropus, and Shisp = Sigmodon hispidus.