Mean pure-strain (black bars) and hybrid (shaded bars) brood sizes. Mean pure-strain is the midparent value. Numbers above the bars indicate heterosis values. Asterisks indicate significance of difference between pure-strains and hybrids in a Student's t test. ***P < 0.001.
Click et al. BMC Evolutionary Biology 2009 9:75 doi:10.1186/1471-2148-9-75