Body size rather than reflectivity explains thermal constraints on colour variation in an aposematic jewel bug

Theory posits that warning signals should converge phenotypically to reinforce predator memory, yet many aposematic species show substantial variation in warning signals within and between populations. This may reflect alternative selection pressures, such as thermoregulation, though empirical tests are limited and often overlook the full solar spectrum. We tested whether thermal trade-offs could explain warning colour variation in the aposematic cotton harlequin bug (Tectocoris diophthalmus), which is sexually dichromatic, varies within sexes, and shows clinal shifts in colour—iridescent blue-green in cooler regions, red–orange in warmer ones. We measured reflectivity across the full solar spectrum and assessed the role of ultraviolet–visible (300–700 nm) and near-infrared (700–1700 nm) light on heating, using a solar simulator and temperature controlled-chamber to isolate the effect of radiative heating. Reflectivity differences between iridescent and non-iridescent patches were ..., We measured the total hemispherical reflectance for a subset of individuals (n = 11), using an integrating sphere. We measured reflectance of the spectral range of 400–2100 nm, and measurements were calibrated against a 99% white reflectance standard and a 2% black reflectance standard. We measured the bugs alive and immediately after euthanasia to validate that reflectance remained similar post-mortem. Although our reflectance measurements do not include UV, our multispectral imaging showed that the bugs do not reflect UV and thus there is no difference in UV reflectance.
We conducted heating experiments using a solar simulator and a closed glass thermal chamber which kept the ambient air temperature in the chamber constant at 20º C. This was to isolate the effect of radiation from the solar simulator and to minimise the effects of convection and conduction. Inside the chamber, the sample bug was placed dorsal side up on a transparent acrylic platform and with a thermocouple inserted i..., , # Body size rather than reflectivity explains thermal constraints on colour variation in an aposematic jewel bug

Dataset DOI: [10.5061/dryad.7pvmcvf4j](10.5061/dryad.7pvmcvf4j)

## Description of the data and file structure

1. **tectocoris_analysis.Rmd** - code for all analyses (reflectivity, heating, and statistical). NOTE: In order for all code to run, please unzip the two zip files (heating_data.zip and bug_pics.zip) located in the \"data\" folder.
2. **specs.xlsx** - raw data from spectrophometer readings, with 3 tabs:
* **bug_specs** contains the spectrophotometer readings from the bugs. The first column \"wl\" represents wavelength in nanometres. Each subsequent column corresponds an individual reflectance measurement of bugs colour patch and shows reflectance (%) at each wavelength.
* Column names follow the naming convention: bug ID, sex, status (all bugs are dead in this dataset), colour category of the measured patch, and the spec ID (eg. \"Splice17__0__03\" or \"Splice17__...,

理论预测，警戒信号应在表型上趋于一致，以强化捕食者的记忆，但许多具有警戒色的（aposematic）物种在种群内部及种群间的警戒信号却存在显著变异。这或许反映了其他选择压力，例如体温调节，但相关实证检验较为匮乏，且往往未覆盖完整的太阳光谱范围。
我们针对具有警戒色的棉斑红蝽（Tectocoris diophthalmus）检验了体温权衡是否可解释其警戒色变异：该物种存在性二色性，且同一性别内也存在体色差异，同时体色呈现地理渐变模式——凉爽区域个体呈现虹彩蓝绿色，温暖区域则为红橙色。我们对完整太阳光谱范围内的反射率进行了测定，并利用太阳模拟器与温控箱分离辐射加热的影响，以此评估紫外-可见光（ultraviolet–visible，300–700 nm）与近红外光（near-infrared，700–1700 nm）对体温升高的作用。
虹彩斑块与非虹彩斑块间的反射率差异为……。我们使用积分球（integrating sphere）对11个个体的子集开展了总半球反射率测定。本次测定覆盖400–2100 nm的光谱范围，所有测量均以99%白反射标准板与2%黑反射标准板进行校准。我们分别对活体个体以及安乐死后即刻的个体进行了反射率测定，以验证死后反射率无显著变化。尽管本次反射率测定未覆盖紫外波段，但多光谱成像结果显示，该蝽虫无紫外反射特性，因此紫外反射率不存在差异。
我们采用太阳模拟器与密闭玻璃热箱开展加热实验，箱内环境空气温度维持在20℃。此举旨在分离太阳模拟器的辐射影响，并尽可能降低对流与热传导的干扰。实验箱内，供试蝽虫以背侧朝上的方式放置于透明亚克力平台上，并插入热电偶以……（原文截断）。
# 体型而非反射率可解释警戒色宝石蝽体色变异的热约束

数据集DOI：[10.5061/dryad.7pvmcvf4j](10.5061/dryad.7pvmcvf4j)

## 数据与文件结构说明
1. **tectocoris_analysis.Rmd**：用于所有分析的代码（涵盖反射率测定、加热实验与统计学分析）。注意：若需完整运行所有代码，请解压"data"文件夹内的两个压缩文件：heating_data.zip与bug_pics.zip。
2. **specs.xlsx**：分光光度计读数的原始数据，包含3个工作表：
* **bug_specs**：该工作表包含蝽虫的分光光度计读数。第一列"wl"代表波长，单位为纳米。后续每一列对应单只蝽虫体色斑块的反射率测量值，展示了对应波长下的反射率（百分比）。
* 列名遵循以下命名规则：蝽虫ID、性别、样本状态（本数据集内所有个体均为死后样本）、被测斑块的体色类别以及光谱ID（例如"Splice17__0__03"或"Splice17__……"）