McClelland et al. 2023 RSOS Hydrophobicity Data.csv from Eggshell composition and surface properties of avian brood-parasitic species compared to non-parasitic species

The eggs of avian obligate brood-parasitic species have multiple adaptations to deceive hosts and optimize development in host nests. While the structure and composition of the eggshell in all birds is essential for embryo growth and protection from external threats, parasitic eggs may face specific challenges such as high microbial loads, rapid laying and ejection by the host parents. We set out to assess whether eggshells of avian brood-parasitic species have either (1) specialized structural properties, to meet the demands of a brood-parasitic strategy or (2) similar structural properties to eggs of their hosts, due to the similar nest environment. We measured the surface topography (roughness), wettability (how well surfaces repel water) and calcium content of eggshells of a phylogenetically and geographically diverse range of brood-parasitic species (representing four of the seven independent lineages of avian brood-parasitic species), their hosts and close relatives of the parasites. These components of the eggshell structure have been demonstrated previously to influence such factors as the risk of microbial infection and overall shell strength. Within a phylogenetically controlled framework, we found no overall significant differences in eggshell roughness, wettability and calcium content between (<i>i</i>) parasitic and non-parasitic species, or (<i>ii</i>) parasitic species and their hosts. Both the wettability and calcium content of the eggs from brood-parasitic species were not more similar to those of their hosts' eggs than expected by chance. By contrast, the mean surface roughness of the eggs of brood-parasitic species was more similar to that of their hosts’ eggs than expected by chance, suggesting brood-parasitic species may have evolved to lay eggs that match the host nest environment for this trait. The lack of significant overall differences between parasitic and non-parasitic species, including hosts, in the traits we measured, suggests that phylogenetic signal, as well as general adaptations to the nest environment and for embryo development, outweigh any influence of a parasitic lifestyle on these eggshell properties.

专性育雏寄生鸟类（avian obligate brood-parasitic species）的鸟卵拥有多重适应性特征，用以骗过宿主并优化其在宿主巢内的发育。尽管所有鸟类的蛋壳结构与组成均对胚胎发育及抵御外界威胁至关重要，但寄生鸟卵仍需应对诸多特殊挑战，例如高微生物负荷、快速产卵以及被宿主亲鸟驱逐。本研究旨在探究，育雏寄生物种的蛋壳是否具备两类特征：其一，为适配育雏寄生策略而演化出的特化结构特性；其二，因栖息于相似巢环境而与宿主鸟卵结构相似的特性。我们针对涵盖7个独立鸟类育雏寄生演化支中的4个、且系统发育与地理分布均具多样性的育雏寄生物种及其宿主与寄生近缘类群，测定了其蛋壳的表面形貌（粗糙度，roughness）、润湿性（wettability，即表面拒水能力）与钙含量。此前已有研究证实，蛋壳结构的上述三类属性会影响微生物感染风险与蛋壳整体强度等性状。在系统发育校正分析框架下，我们未发现寄生与非寄生鸟类间，或寄生物种与其宿主间在蛋壳粗糙度、润湿性与钙含量上存在总体显著差异。育雏寄生物种鸟卵的润湿性与钙含量，并未比随机预期结果更接近其宿主鸟卵的对应性状。与之相反，育雏寄生物种鸟卵的平均表面粗糙度，比随机预期结果更接近其宿主鸟卵的对应性状，这表明育雏寄生物种可能已演化出在该性状上匹配宿主巢环境的产卵策略。我们所测定的性状在寄生与非寄生物种（包括宿主）间未出现总体显著差异，这表明系统发育信号，以及对巢环境与胚胎发育的一般性适应，其对蛋壳性状的影响要强于寄生生活方式带来的影响。