Batesian mimicry, in which harmless organisms resemble unpalatable or harmful species, is a well‐studied adaptation for predation avoidance. The females of some Batesian mimic species comprise mimetic and nonmimetic individuals. Mimetic females of such polymorphic species clearly have a selective advantage due to decreased predation pressure, but the selective forces that maintain nonmimetic females in a population remain unclear. In the swallowtail butterfly, Papilio polytes, female polymorphism is controlled by the H (mimetic) and h (nonmimetic) alleles at a single autosomal locus. Here, we examined whether the dominant H allele has a deleterious effect on the pre‐adult survival rate (egg‐to‐adult emergence rate). We repeated an assortative mating‐like treatment—that is breeding of males and females whose mothers had the same phenotype (mimetic or nonmimetic)—for three consecutive generations, while avoiding inbreeding. Results showed that pre‐adult survival rate decreased over generations only in lines derived from mothers with the mimetic phenotype (hereafter, mimetic‐assorted lines). This lowered survival was due to an increased mortality at the final instar larval stage and the pupal stages. Interestingly, the pre‐adult mortality in the mimetic‐assorted lines seemed to be associated with a male‐biased sex ratio at adult emergence. These results suggest that the dominant H allele displays a mildly deleterious effect that is expressed more strongly in females and homozygous individuals than in heterozygous individuals. We propose that this cost of mimicry in larval and pupal stages contributes to the maintenance of female‐limited polymorphism in P. polytes.

中文翻译：

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拟态基因降低凤蝶多类动物的成体前存活率：一种在贝氏拟态中维持雌性有限多态性的可能新机制

贝氏拟态，其中无害的生物体类似于难吃或有害的物种，是一种经过充分研究的避免捕食的适应性。一些贝氏拟态物种的雌性包括拟态个体和非拟态个体。由于捕食压力降低，这种多态性物种的拟态雌性显然具有选择优势，但在种群中维持非拟态雌性的选择力仍不清楚。在燕尾蝶 Papilio polytes 中，雌性多态性由单个常染色体位点的 H（模拟）和 h（非模拟）等位基因控制。在这里，我们检查了显性 H 等位基因是否对成虫前存活率（卵到成虫出现率）产生有害影响。我们连续三代重复了一种类似交配的处理——即繁殖具有相同表型（模仿或非模仿）的母亲的雄性和雌性，同时避免近亲繁殖。结果表明，仅在来自具有模拟表型的母亲的品系（以下称为模拟分类品系）中，成虫前存活率会随着世代的推移而下降。这种降低的存活率是由于最后龄幼虫阶段和蛹阶段的死亡率增加。有趣的是，拟态组合品系中的成年前死亡率似乎与成年出现时偏向男性的性别比例有关。这些结果表明显性 H 等位基因显示出轻微的有害作用，在女性和纯合个体中比在杂合个体中表达得更强烈。