Results from Crosses between Spontaneously Haploidized Diploid Strains and the Haploid Ancestor

<p>MGR of progeny of a sexual cross of three spontaneously haploidized diploid strains (A, B, and C; see <a href="http://www.plosgenetics.org/article/info:doi/10.1371/journal.pgen.0030068#pgen-0030068-g002" target="_blank">Figure 2</a>B) and the haploid ancestor. For each cross, 40 progeny were analyzed. The solid arrow indicates the MGR class containing the evolved haploidized parent, the dashed arrow indicates the MGR class of the haploid nonevolved ancestral strain (WG631). The variety of MGRs found among the progeny and the absence of clear phenotypic classes indicates the presence of multiple adaptive mutations. Most combinations of these mutations give rise to a MGR intermediate between the values of the two parents of the cross. In all crosses considerable genetic variation in MGR exists among the 40 progeny (ANOVA data: A, <i>F</i>_39,163 = 12.43, <i>p</i> < 0.0001; B, <i>F</i>_39,195 = 35.09, <i>p</i> < 0.0001; C, <i>F</i>_39,192 = 63.45, <i>p</i> < 0.0001). We compared the MGR of the progeny with the lowest MGR of each cross with the MGR of the ancestral stain (WG561 and WG615) and found that for two crosses this MGR is significantly lower than the MGR of the ancestor (A, <i>t</i>₁₆ = 1.04, <i>p</i> = 0.31; B, <i>t</i>₁₆ = 4.77, <i>p</i> = 0.00020; C, <i>t</i>₁₃ = 6.57, <i>p</i> < 0.0001).