Comparison of mean Tajima's D between fester and housekeeping genes. Fester genes are labeled "F", and housekeeping genes are labeled "H". There are four fester values: A-type East Coast, A-type West Coast, B1-type East Coast, C-type East Coast. Mean Tajima's D values for housekeeping genes were obtained by averaging across all six populations (Falmouth, MA, Quissett, MA, Sandwich, MA, Monterey, CA, Santa Barbara, CA and Seattle, WA). The bars from left to right correspond to the following genes: 60S ribosomal protein L13, vasa, heat shock cognate 71kda protein, vigilin, 60S ribosomal protein L10, ADP/ATP translocase 3, heat shock protein HSP-90 beta, cytoplasmic actin 2, 60S ribosomal protein L8, mitochondrial COI, 40S ribosomal protein 3A, adult-type muscle actin 2, 60S ribosomal protein L6, fester B1-type East Coast, fester A-type West Coast, fester C-type East Coast, and fester A-type East Coast.