Data from: A scenario for the evolution of selective egg colouration: the roles of enemy-free space, camouflage, thermoregulation, and pigment limitation

Behavioural plasticity can drive the evolution of new traits in animals. In oviparous species, plasticity in oviposition behaviour could promote the evolution of new egg traits by exposing them to different selective pressures in novel oviposition sites. Individual females of the predatory stink bug Podisus maculiventris are able to selectively colour their eggs depending on leaf side, laying lightly pigmented eggs on leaf undersides and more pigmented eggs, which are more resistant to ultraviolet (UV) radiation damage, on leaf tops. Here, we propose an evolutionary scenario for P. maculiventris egg pigmentation and its selective application. We experimentally tested the influence of several ecological factors that: (i) could have favoured a behavioural shift towards laying eggs on leaf tops and thus the evolution of a UV-protective egg pigment (i.e. exploitation of enemy-reduced space or a thermoregulatory benefit) and (ii) could have subsequently led to the evolution of selective pigment application (i.e. camouflage or costly pigment production). We found evidence that a higher predation pressure on leaf undersides could have caused a shift in oviposition effort towards leaf tops. We also found the first evidence of an insect egg pigment providing a thermoregulatory advantage. Our study contributes to an understanding of how plasticity in oviposition behaviour could shape the responses of organisms to ecological factors affecting their reproductive success, spurring the evolution of new morphological traits.

行为可塑性可推动动物新性状的演化。在卵生（oviparous）物种中，产卵行为（oviposition behaviour）的可塑性可通过使卵暴露于新颖产卵位点的差异化选择压力之下，促进卵相关新性状的演化。捕食性蝽类斑腹刺益蝽（Podisus maculiventris）的雌性个体可根据叶片朝向选择性地为卵着色：在叶背产下色素沉着较浅的卵，而在叶面产下对紫外线（ultraviolet, UV）辐射损伤具有更高抗性的高色素卵。本研究针对斑腹刺益蝽的卵色素沉着及其选择性着色过程提出了一套演化假说。我们通过实验检验了两类生态因子的影响：其一，这类因子可能推动向叶面产卵的行为转变，进而演化出具备紫外线防护功能的卵色素（即利用天敌密度更低的空间或获得体温调节优势）；其二，这类因子可能后续促使选择性着色行为的演化（即实现伪装或权衡色素生产的成本投入）。研究结果表明，叶背更高的捕食压力可能是促使产卵行为转向叶面的诱因。本研究同时首次获得了昆虫卵色素可带来体温调节优势的实验证据。本研究有助于深入理解产卵行为的可塑性如何塑造生物体对影响其繁殖成功的生态因子的响应，并推动新形态性状的演化。