DNA for genotyping was isolated from 1.0–2.0 mm tail clips by digesting with Proteinase K (Fisher) at 55°C in a buffer composed of 0.45% NP40 (Sigma), 0.45% Tween 20 (Fisher) and 1X PCR buffer (Promega). The product of this digestion was diluted (1:10) in sterile H2O and used for genotyping without further purification. Microsatellite genotyping was performed using standard PCR and gel electrophoresis protocols. Reaction conditions for each marker are listed in Additional File 1 and 2.