McClelland et al. 2023 RSOS Calcium Data.csv from Eggshell composition and surface properties of avian brood-parasitic species compared with 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) parasitic and non-parasitic species, or (ii) 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）的卵具备多重适应性，以欺骗宿主并优化其在宿主巢内的发育进程。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，但寄生卵需应对诸多特殊挑战，例如高微生物负载、快速产卵以及宿主亲鸟的卵排斥行为。本研究旨在探究育雏寄生鸟类的蛋壳是否具备以下两类特征之一：(1) 适配育雏寄生策略的特化结构属性；或(2) 因巢环境相似而与宿主卵结构属性趋同。我们对多个系统发育与地理分布均具多样性的育雏寄生类群（涵盖7个独立育雏寄生鸟类支系中的4个）、其宿主以及寄生鸟类的近缘物种的蛋壳开展了三项指标测定：表面形貌（surface topography，即粗糙度）、润湿性（wettability，即表面斥水能力）以及钙含量（calcium content）。此前已有研究证实，蛋壳结构的这些属性会影响微生物感染风险与蛋壳整体强度等性状。在系统发育校正的分析框架下，我们发现：(1) 寄生鸟类与非寄生鸟类之间，以及(2) 寄生鸟类与其宿主之间，蛋壳粗糙度、润湿性与钙含量均无整体显著性差异。育雏寄生鸟类卵的润湿性与钙含量，并未较随机预期更接近其宿主卵的对应指标。与之相反，育雏寄生鸟类卵的平均表面粗糙度，较随机预期更接近其宿主卵的对应指标，这表明育雏寄生鸟类可能已演化出在该性状上匹配宿主巢环境的产卵策略。本研究测定的性状在寄生鸟类与包括宿主在内的非寄生鸟类间均无整体显著性差异，这表明系统发育信号、对巢环境与胚胎发育的通用适应性，均强于寄生生活方式对这些蛋壳属性的影响。