Comparison of intergenic spacers (IGSs) in B. pennsylvanicus and B. floridanus. (A) A significant relationship in the lengths of homologous spacers implies a certain conservation of spacer length (Spearman's ρ = 0.7895; p < 0.0001), but B. pennsylvanicus IGSs are generally longer (average 290 bp) than those of B. floridanus (average 180 bp) (Wilcoxon Rank sum test, p < 0.0001). Homologous spacers were identified based on their positions in the genomes. IGSs that lacked a homolog were excluded. (B) B. pennsylvanicus IGSs (open circles) generally have lower %GC and shorter lengths than ORFs (filled squares). Horizontal lines mark the average %GC for ORFS (32.1%; solid line) and IGSs (20.0%; dashed line). Additionally the base composition of all homologous, nonzero IGSs were compared and show no strong correlation, yet cluster around ∼20% GC in both genomes (unpublished data).
