Data for: Ebony underpins Batesian mimicry in melanic stoneflies

The evolution of Batesian mimicry – whereby harmless species avoid
predation through their resemblance to harmful species – has long
intrigued biologists. In rare cases, Batesian mimicry is linked to
intraspecific colour variation, in which only some individuals within a
population resemble a noxious ‘model’. Here, we assess intraspecific
colour variation within a widespread New Zealand stonefly, wherein highly
melanised individuals of Zelandoperla closely resemble a chemically
defended aposematic stonefly, Austroperla cyrene. We assess convergence in
the colour pattern of these two species, compare their relative
palatability to predators, and use genome-wide association mapping to
assess the genetic basis of this resemblance. Our analysis reveals that
melanised Zelandoperla overlap significantly with Austroperla in colour
space, but are significantly more palatable to predators, implying that
they are indeed Batesian mimics. Analysis of 194,773 genome-wide SNPs
reveals an outlier locus (ebony) strongly differentiating melanic versus
non-melanic Zelandoperla. Genotyping of 338 specimens from a single
Zelandoperla population indicates that ebony explains nearly 70% of the
observed variance in melanism. As ebony has a well-documented role in
insect melanin biosynthesis, our findings indicate this locus has a
conserved function across deeply divergent hexapod lineages.
Distributional records suggest a link between the occurrence of melanic
Zelandoperla and the forested ecosystems where the model Austroperla is
abundant, suggesting the potential for adaptive shifts in this system
underpinned by environmental change.

贝茨拟态（Batesian mimicry）的演化机制——即无害物种通过模拟有害物种的外形以规避捕食——长期以来一直是生物学家关注的核心议题之一。在极少数情况下，贝茨拟态会与种内体色变异相关联，即种群内仅部分个体能够模拟具有化学防御能力的‘模型物种’。本研究以一种分布广泛的新西兰石蝇为研究对象，对其种内体色变异展开分析：该类群中高度黑化的泽兰襀属（Zelandoperla）个体，与具有化学防御机制的警戒色石蝇——澳石蝇（Austroperla cyrene）——外形高度相似。本研究对这两个物种的体色模式趋同性进行了评估，比较二者对捕食者的相对适口性，并通过全基因组关联作图（genome-wide association mapping）解析该拟态相似性的遗传基础。分析结果显示，黑化泽兰襀个体与澳石蝇在色彩空间中的分布存在显著重叠，但前者对捕食者的适口性显著更高，这表明它们确实属于典型的贝茨拟态物种。对194773个全基因组单核苷酸多态性位点（SNPs）的分析表明，一个异常位点（黑檀基因ebony）能够显著区分黑化与非黑化的泽兰襀个体。对来自单个泽兰襀种群的338份标本进行基因分型后发现，黑檀基因能够解释近70%的黑化性状观测变异。鉴于黑檀基因在昆虫黑色素生物合成中的功能已有充分研究佐证，本研究结果显示，该位点在亲缘关系极远的六足类支系中均具有保守功能。分布记录显示，黑化泽兰襀的出现与模型物种澳石蝇富集的森林生态系统存在显著关联，这表明该系统存在由环境变化驱动的适应性演化潜力。