Reduction in the cumulative effect of stress-induced inbreeding depression due to intra-generational purging in Drosophila melanogaster

Environmental stress generally exacerbates the harmful effects of inbreeding and it has been proposed that this could be exploited in purging deleterious alleles from threatened inbred populations. However, understanding what factors contribute to variability in the strength of inbreeding depression (ID) observed across adverse environmental conditions remains a challenge. Here, we examined how the nature and timing of stress affects ID and the potential for purging using inbred and outbred Drosophila melanogaster larvae exposed to biotic (larval competition, bacteria infection) and abiotic (ethanol, heat) stressors compared with unstressed controls. ID was measured during (larval survival) and after (male mating success) stress exposure. The level of stress imposed by each stressor was approximately equal, averaging a 42% reduction in outbred larval survival relative to controls. All stressors induced on average the same ID, causing a threefold increase in lethal equivalents for larval...环境胁迫通常会加剧近交产生的有害效应，已有研究提出可利用这一特性从受威胁的近交种群中清除有害等位基因。然而，阐明哪些因素会导致不同逆境条件下观测到的近交衰退（inbreeding depression，下文简称ID）强度存在差异，仍是一项亟待解决的研究难题。本研究以近交与远交的黑腹果蝇（Drosophila melanogaster）幼虫为实验材料，将其分别暴露于生物胁迫（幼虫竞争、细菌感染）与非生物胁迫（乙醇、高温）环境中，并设置未受胁迫的对照组，以此探究胁迫的类型与作用时机如何影响近交衰退，以及种群清除有害等位基因的潜力。本研究在胁迫暴露期间（以幼虫存活率为指标）及暴露后（以雄性交配成功率为指标）对近交衰退程度进行了量化测定。各胁迫因子施加的胁迫强度大致相当，相较于对照组，远交幼虫的存活率平均降低了42%。所有胁迫因子平均诱导产生的近交衰退程度一致，使幼虫的致死当量数量提升至原来的三倍……