Data from: Linking isotopes and panmixia: high within-colony variation in feather δ2H, δ13C, and δ15N across the range of the American white pelican

Complete panmixia across the entire range of a species is a relatively rare phenomenon; however, this pattern may be found in species that have limited philopatry and frequent dispersal. American white pelicans (Pelecanus erythrorhyncos) provide a unique opportunity to examine the role of long-distance dispersal in facilitating gene flow in a species recently reported as panmictic across its broad breeding range. This species is also undergoing a range expansion, with new colonies arising hundreds of kilometers outside previous range boundaries. In this study, we use a multiple stable isotope (δ2H, δ13C, δ15N) approach to examine feather isotopic structuring at 19 pelican colonies across North America, with the goal of establishing an isotopic basemap that could be used for assigning individuals at newly established breeding sites to source colonies. Within-colony isotopic variation was extremely high, exceeding 100‰ in δ2H within some colonies (with relatively high variation also observed for δ13C and δ15N). The high degree of within-site variation greatly limited the utility of assignment-based approaches (42% cross-validation success rate; range: 0–90% success). Furthermore, clustering algorithms identified four likely isotopic clusters; however, those clusters were generally unrelated to geographic location. Taken together, the high degree of within-site isotopic variation and lack of geographically-defined isotopic clusters preclude the establishment of an isotopic basemap for American white pelicans, but may indicate that a high incidence of long-distance dispersal is facilitating gene flow, leading to genetic panmixia.

在物种的整个分布范围内实现完全泛交（panmixia）是较为罕见的现象，但该繁殖模式可见于恋巢性（philopatry）有限且频繁发生扩散的物种。美国白鹈鹕（Pelecanus erythrorhyncos）为研究长距离扩散在促进基因流中的作用提供了独特契机——该物种近期被报道在其广阔的繁殖分布范围内呈现泛交特征。该物种同时正经历分布范围扩张，新繁殖群会在距原分布边界数百公里的区域形成。本研究采用多重稳定同位素（δ2H、δ13C、δ15N）方法，对北美19个鹈鹕繁殖群的羽毛同位素结构进行分析，旨在建立同位素基础图谱，用于将新建立繁殖地的个体溯源至其起源繁殖群。各繁殖群内部的同位素变异程度极高，部分群体的δ2H变异幅度超过100‰，δ13C与δ15N同样观测到显著变异。群体内的高同位素变异极大限制了个体溯源方法的应用效能，交叉验证成功率仅为42%，成功率区间为0%至90%。此外，聚类算法识别出4个潜在同位素聚类群，但这些聚类群与地理分布基本无关联。综合来看，群体内高同位素变异与无地理关联的同位素聚类特征，使得无法为美国白鹈鹕构建同位素基础图谱，但这也暗示长距离扩散事件频发，促进了基因交流，最终导致种群遗传泛交。