Walling Craig A, Stamper Clare E, Smiseth Per T, Moore Allen J
Centre for Ecology and Conservation, School of Biosciences, University of Exeter, Cornwall Campus, Penryn, Cornwall TR10 9EZ, United Kingdom.
Proc Natl Acad Sci U S A. 2008 Nov 25;105(47):18430-5. doi: 10.1073/pnas.0803146105. Epub 2008 Nov 13.
Sex differences in parenting are common in species where both males and females provide care. Although there is a considerable body of game and optimality theory for why the sexes should differ in parental care, genetics can also play a role, and no study has examined how genetic influences might influence differences in parenting. We investigated the extent that genetic variation influenced differences in parenting, whether the evolution of differences could be constrained by shared genetic influences, and how sex-specific patterns of genetic variation underlying parental care might dictate which behaviors are free to evolve in the burying beetle Nicrophorus vespilloides. Females provided more direct care than males but did not differ in levels of indirect care or the number of offspring they were willing to rear. We found low to moderate levels of heritability and evolvability for all 3 parenting traits in both sexes. Intralocus sexual conflict was indicated by moderately strong intersex genetic correlations, but these were not so strong as to represent an absolute constraint to the evolution of sexual dimorphism in care behavior. Instead, the pattern of genetic correlations between parental behaviors showed sex-specific tradeoffs. Thus, differences in the genetic correlations between parental traits within a sex create sex-specific lines of least evolutionary resistance, which in turn produce the specific patterns of sex differences in parental care. Our results therefore suggest a mechanism for the evolution of behavioral specialization during biparental care if uniparental and biparental care behaviors share the same genetic influences.
在双亲都参与抚育后代的物种中，亲代抚育存在性别差异是很常见的。尽管有大量的博弈论和最优性理论来解释两性在亲代抚育方面为何会存在差异，但基因也可能发挥作用，而且尚无研究探讨基因影响如何影响亲代抚育的差异。我们研究了基因变异在多大程度上影响亲代抚育的差异，差异的进化是否会受到共享基因影响的限制，以及亲代抚育背后基因变异的性别特异性模式如何决定埋葬虫（Nicrophorus vespilloides）中哪些行为能够自由进化。雌性提供的直接抚育比雄性更多，但在间接抚育水平或愿意抚养的后代数量上没有差异。我们发现两性的这三种亲代抚育特征的遗传力和进化潜力都处于低到中等水平。适度较强的两性间遗传相关性表明存在基因座内的性冲突，但这些相关性并不强到足以对抚育行为的两性异形进化构成绝对限制。相反，亲代行为之间的遗传相关性模式显示出性别特异性的权衡。因此，同一性别内亲代特征之间遗传相关性的差异产生了性别特异性的最小进化阻力线，进而产生了亲代抚育中性别差异的特定模式。所以我们的研究结果表明，如果单亲抚育行为和双亲抚育行为受到相同的基因影响，那么在双亲抚育过程中行为特化的进化就存在一种机制。
