Partridge Linda, Fowler Kevin
Institute of Cell, Animal and Population Biology, University of Edinburgh, Zoology Building, West Mains Rd, Edinburgh, EH9 3JT, UK.
Evolution. 1992 Feb;46(1):76-91. doi: 10.1111/j.1558-5646.1992.tb01986.x.
Aging may be a consequence of mutation accumulation or of negative pleiotropic correlations between performance late and earlier in the lifespan. This study used artificial selection on flies derived from two different base stocks to produce "young" and "old" lines, propagated by breeding from young and old adults respectively. Virgin and mated adults of both sexes from the "old" lines lived longer than "young" line flies. "Young" and "old" mated females did not differ in fecundity or fertility early in the lifespan, but "old" line females had higher fecundity and fertility late in life. The results therefore suggested either that the response to selection had revealed the effect of mutation accumulation, or that pleiotropy involving characters other than early fecundity must have been involved. Development time from egg to adult was longer in the "old" lines. Competition of selected line larvae from one base stock against mutant marked larvae from the same base stock revealed that, at a wide range of larval densities, "old" line larvae showed lower survival rates than "young" line larvae. Thorax length and wet weight were significantly greater in the "old" line flies from one base stock. The results may imply that the selection regime in the "old" lines favored extended growth during development to produce a more durable adult soma, despite the cost in increased larval mortality and delayed reproduction, because the potential reproductive benefits later in life were increased. However, the differences between larvae from "old" and "young" lines could also be attributable to density differences, and this possibility needs systematic investigation.
衰老可能是突变积累的结果，也可能是寿命后期与早期表现之间负向多效性关联的结果。本研究对源自两种不同基础种群的果蝇进行人工选择，以培育出“年轻”和“年老”品系，分别通过年轻成虫和老龄成虫繁殖来传代。“年老”品系的未交配和已交配的雌雄成虫寿命均长于“年轻”品系的果蝇。“年轻”和“年老”已交配雌蝇在寿命早期的繁殖力和生育力并无差异，但“年老”品系雌蝇在寿命后期具有更高的繁殖力和生育力。因此，结果表明，对选择的响应要么揭示了突变积累的影响，要么一定涉及了除早期繁殖力之外的其他性状的多效性。“年老”品系从卵到成虫的发育时间更长。将来自一种基础种群的选定品系幼虫与来自同一基础种群的突变标记幼虫进行竞争，结果显示，在广泛的幼虫密度范围内，“年老”品系幼虫的存活率低于“年轻”品系幼虫。来自一种基础种群的“年老”品系果蝇的胸长和湿重显著更大。结果可能意味着，“年老”品系中的选择机制有利于发育过程中的延长生长，以产生更持久的成虫躯体，尽管代价是幼虫死亡率增加和繁殖延迟，因为后期潜在的繁殖益处增加了。然而，“年老”和“年轻”品系幼虫之间的差异也可能归因于密度差异，这种可能性需要进行系统研究。
