Department of Biology, Queen's University, Kingston, ON, Canada.
BMC Evol Biol. 2011 Jun 6;11:156. doi: 10.1186/1471-2148-11-156.
Sex differences in the magnitude or direction of mutational effect may be important to a variety of population processes, shaping the mutation load and affecting the cost of sex itself. These differences are expected to be greatest after sexual maturity. Mutation-accumulation (MA) experiments provide the most direct way to examine the consequences of new mutations, but most studies have focused on juvenile viability without regard to sex, and on autosomes rather than sex chromosomes; both adult fitness and X-linkage have been little studied. We therefore investigated the effects of 50 generations of X-chromosome mutation accumulation on the fitness of males and females derived from an outbred population of Drosophila melanogaster.
Fitness declined rapidly in both sexes as a result of MA, but adult males showed markedly greater fitness loss relative to their controls compared to females expressing identical genotypes, even when females were made homozygous for the X. We estimate that these mutations are partially additive (h ~ 0.3) in females. In addition, the majority of new mutations appear to harm both males and females.
Our data helps fill a gap in our understanding of the consequences of sexual selection for genetic load, and suggests that stronger selection on males may indeed purge deleterious mutations affecting female fitness.
突变效应的大小或方向的性别差异可能对各种群体过程很重要，塑造突变负荷并影响性本身的成本。这些差异预计在性成熟后最大。突变积累 (MA) 实验提供了最直接的方法来检查新突变的后果，但大多数研究都集中在幼体活力上，而不考虑性别，并且集中在常染色体上，而不是性染色体上；成人适应性和 X 连锁都很少被研究。因此，我们调查了 50 代 X 染色体突变积累对来自黑腹果蝇外群的雄性和雌性适应性的影响。
由于 MA，两性的适应性迅速下降，但与表达相同基因型的对照相比，雄性的适应性损失明显更大，即使雌性对 X 染色体为纯合子。我们估计这些突变在雌性中部分是累加的（h ~ 0.3）。此外，大多数新突变似乎对雄性和雌性都有害。
我们的数据有助于填补我们对遗传负荷的性选择后果的理解中的空白，并表明对雄性的更强选择确实可能消除影响雌性适应性的有害突变。
