Data from: Maladaptive plasticity masks the effects of natural selection in the red-shouldered soapberry bug

Natural selection can produce local adaptation, but local adaptation can be masked by maladaptive plasticity. Maladaptive plasticity may arise as a result of gene flow producing novel gene combinations that have not been exposed to selection. In the 1980s, populations of the red-shouldered soapberry bug (Jadera haematoloma) were locally adapted to feed on the seeds of a native host plant and an introduced host plant; by 2014, local differentiation in beak length had been lost, likely as a consequence of increased gene flow. In this study, I assess the relative contributions of natural selection and plasticity to beak length on these two hosts. I confirm the earlier hypothesis that the host plant seedpod drives divergent natural selection on beak length. I then demonstrate that the proximate cause of the loss of observable differentiation in beak length is maladaptive plasticity, which masks persistent genetic differences between host-associated populations. Maladaptive plasticity is highest in areas where the two plants co-occur; in combination with historical measures of plasticity in hybrids, this indicates that maladaptive plasticity may be a consequence of ongoing gene flow. Although natural selection produced locally adapted genotypes in soapberry bugs, maladaptive plasticity is masking phenotypic differences between populations in nature.自然选择可产生本地适应，但本地适应可被适应不良的表型可塑性（maladaptive plasticity）所掩盖。适应不良的表型可塑性可能源于基因流（gene flow）产生了未曾经历选择的全新基因组合。20世纪80年代，红肩实球蝽（Jadera haematoloma）的不同种群已分别适应取食本土宿主植物与入侵宿主植物的种子；至2014年，其喙长（beak length）的种群间本地分化已消失，这一现象大概率由基因流增强所致。本研究旨在评估自然选择与表型可塑性对这两种宿主植物上红肩实球蝽喙长的相对贡献。本研究验证了此前提出的假说：宿主植物的果荚对红肩实球蝽喙长施加了分化性自然选择（divergent natural selection）压力。随后本研究证实，喙长可观测分化消失的直接诱因是适应不良的表型可塑性，该效应掩盖了不同宿主关联种群（host-associated populations）间持续存在的遗传差异。适应不良的表型可塑性在两种宿主植物共存的区域最为显著；结合此前对杂交种群（hybrids）可塑性的测定结果，这表明适应不良的表型可塑性可能是持续基因流的产物。尽管自然选择在红肩实球蝽种群中塑造了本地适应型基因型，但适应不良的表型可塑性掩盖了自然种群间的表型差异。