Fox C W, Czesak M E, Wallin W G
Department of Entomology, Agricultural Science Center North, University of Kentucky, Lexington, KY 40546, USA.
J Evol Biol. 2004 Sep;17(5):1007-17. doi: 10.1111/j.1420-9101.2004.00752.x.
Evolutionary responses to selection can be complicated when there is substantial nonadditivity, which limits our ability to extrapolate from simple models of selection to population differentiation and speciation. Studies of Drosophila melanogaster indicate that lifespan and the rate of senescence are influenced by many genes that have environment- and sex-specific effects. These studies also demonstrate that interactions among alleles (dominance) and loci (epistasis) are common, with the degree of interaction differing between the sexes and among environments. However, little is known about the genetic architecture of lifespan or mortality rates for organisms other than D. melanogaster. We studied genetic architecture of differences in lifespan and shapes of mortality curves between two populations of the seed beetle, Callosobruchus maculatus (South India and Burkina Faso populations). These two populations differ in various traits (such as body size and adult lifespan) that have likely evolved via host-specific selection. We found that the genetic architecture of lifespan differences between populations differs substantially between males and females; there was a large maternal effect on male lifespan (but not on female lifespan), and substantial dominance of long-life alleles in females (but not males). The large maternal effect in males was genetically based (there was no significant cytoplasmic effect) likely due to population differences in maternal effects genes that influence lifespan of progeny. Rearing host did not affect the genetic architecture of lifespan, and there was no evidence that genes on the Y-chromosome influence the population differences in lifespan. Epistatic interactions among loci were detectable for the mortality rate of both males and females, but were detectable for lifespan only after controlling for body size variation among lines. The detection of epistasis, dominance, and sex-specific genetic effects on C. maculatus lifespan is consistent with results from line cross and quantitative trait locus studies of D. melanogaster.
当存在大量非加性效应时，对选择的进化反应可能会很复杂，这限制了我们从简单的选择模型推断种群分化和物种形成的能力。对黑腹果蝇的研究表明，寿命和衰老速率受许多具有环境和性别特异性效应的基因影响。这些研究还表明，等位基因之间的相互作用（显性）和基因座之间的相互作用（上位性）很常见，且相互作用程度在性别之间和不同环境中有所不同。然而，对于除黑腹果蝇之外的其他生物，其寿命或死亡率的遗传结构知之甚少。我们研究了两种豆象（Callosobruchus maculatus，南印度种群和布基纳法索种群）在寿命差异和死亡率曲线形状方面的遗传结构。这两个种群在各种性状（如体型和成虫寿命）上存在差异，这些性状可能是通过宿主特异性选择进化而来的。我们发现，种群间寿命差异的遗传结构在雄性和雌性之间存在很大差异；母体对雄性寿命有很大影响（对雌性寿命则没有），并且长寿等位基因在雌性中占主导地位（在雄性中则没有）。雄性中较大的母体效应是基于遗传的（没有显著的细胞质效应），这可能是由于影响后代寿命的母体效应基因存在种群差异。饲养宿主并未影响寿命的遗传结构，也没有证据表明Y染色体上的基因会影响寿命的种群差异。对于雄性和雌性的死亡率，都可以检测到基因座之间的上位性相互作用，但只有在控制品系间体型差异后，才能检测到寿命方面的上位性相互作用。对豆象寿命的上位性、显性和性别特异性遗传效应的检测结果与黑腹果蝇的品系杂交和数量性状基因座研究结果一致。
